[{"Name":"Types of Skeletal Systems","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"The Exoskeleton","Duration":"6m 25s","ChapterTopicVideoID":28735,"CourseChapterTopicPlaylistID":286919,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.380","Text":"Well, I\u0027m very glad that you\u0027re back with more videos."},{"Start":"00:04.380 ","End":"00:07.320","Text":"Now there are going to be a whole bunch of videos that are going to discuss"},{"Start":"00:07.320 ","End":"00:11.560","Text":"the skeletal systems of various organisms and,"},{"Start":"00:11.560 ","End":"00:15.464","Text":"of course, we\u0027re going to concentrate primarily on humans."},{"Start":"00:15.464 ","End":"00:17.490","Text":"What\u0027s a skeletal system?"},{"Start":"00:17.490 ","End":"00:20.655","Text":"Skeletal system is necessary to support the body."},{"Start":"00:20.655 ","End":"00:22.410","Text":"It\u0027s going to be something which is going to be"},{"Start":"00:22.410 ","End":"00:25.380","Text":"hard and therefore it\u0027s going to be able to"},{"Start":"00:25.380 ","End":"00:31.470","Text":"protect internal organs and it\u0027s going to allow for the movement of an organism."},{"Start":"00:31.470 ","End":"00:34.710","Text":"Now interestingly, there are actually"},{"Start":"00:34.710 ","End":"00:38.060","Text":"3 different skeleton designs in"},{"Start":"00:38.060 ","End":"00:42.980","Text":"various organisms that fulfill the functions that we just mentioned before."},{"Start":"00:42.980 ","End":"00:47.210","Text":"One, the first one is a hydrostatic skeleton."},{"Start":"00:47.210 ","End":"00:49.850","Text":"Actually, this is not a hard skeleton,"},{"Start":"00:49.850 ","End":"00:52.250","Text":"it\u0027s a fluid-based support that we\u0027ll find,"},{"Start":"00:52.250 ","End":"00:54.920","Text":"for instance, in earthworms."},{"Start":"00:54.920 ","End":"00:59.270","Text":"There\u0027s water pressure inside that\u0027s"},{"Start":"00:59.270 ","End":"01:04.340","Text":"inside this earthworm which is creating some structure,"},{"Start":"01:04.340 ","End":"01:08.053","Text":"some pressure that is keeping its shape,"},{"Start":"01:08.053 ","End":"01:10.250","Text":"and we\u0027ll see how that works in a minute."},{"Start":"01:10.250 ","End":"01:13.030","Text":"Then there\u0027s something called an exoskeleton."},{"Start":"01:13.030 ","End":"01:15.320","Text":"That\u0027s a shell that\u0027s on the outside of"},{"Start":"01:15.320 ","End":"01:19.495","Text":"the organism and it does have hard parts on the outside."},{"Start":"01:19.495 ","End":"01:22.155","Text":"We\u0027ll look at that a little bit more in detail."},{"Start":"01:22.155 ","End":"01:24.840","Text":"Then, finally, there\u0027s the endoskeleton."},{"Start":"01:24.840 ","End":"01:26.480","Text":"That\u0027s the skeleton we all think about,"},{"Start":"01:26.480 ","End":"01:30.775","Text":"the bones that we have inside of the human body."},{"Start":"01:30.775 ","End":"01:36.020","Text":"That\u0027s where we\u0027re going to concentrate most of this discussion."},{"Start":"01:36.020 ","End":"01:39.485","Text":"Now let\u0027s go back and start our discussion"},{"Start":"01:39.485 ","End":"01:42.665","Text":"with the hydrostatic skeleton that I mentioned,"},{"Start":"01:42.665 ","End":"01:46.385","Text":"for instance, is inside an earthworm but not only."},{"Start":"01:46.385 ","End":"01:54.079","Text":"It\u0027s formed by a fluid-filled compartment which is under pressure."},{"Start":"01:54.079 ","End":"01:56.510","Text":"There has to be some pressure there."},{"Start":"01:56.510 ","End":"02:01.145","Text":"The organs within this compartment are supported by that aqueous fluid."},{"Start":"02:01.145 ","End":"02:05.570","Text":"In other words, it\u0027s floating in that aqueous fluid and it"},{"Start":"02:05.570 ","End":"02:10.804","Text":"also resists internal compression because there is some sort of a skin,"},{"Start":"02:10.804 ","End":"02:12.790","Text":"some sort of membrane around it,"},{"Start":"02:12.790 ","End":"02:15.095","Text":"so if it\u0027s compressed,"},{"Start":"02:15.095 ","End":"02:19.670","Text":"the pressure there keeps it more or less in its own shape."},{"Start":"02:19.670 ","End":"02:24.365","Text":"It\u0027s found in soft-bodied animals such as sea anemones,"},{"Start":"02:24.365 ","End":"02:26.135","Text":"earthworms that we mentioned,"},{"Start":"02:26.135 ","End":"02:31.220","Text":"Cnidaria, that\u0027s different kinds of invertebrates,"},{"Start":"02:31.220 ","End":"02:34.855","Text":"for instance, the kind you see over here on the right."},{"Start":"02:34.855 ","End":"02:40.804","Text":"Now let\u0027s list see then how something can move even if it has no skeleton,"},{"Start":"02:40.804 ","End":"02:43.130","Text":"even if it has no hard skeleton,"},{"Start":"02:43.130 ","End":"02:46.010","Text":"that is, say a hydrostatic skeleton."},{"Start":"02:46.010 ","End":"02:48.175","Text":"Let\u0027s look at earthworms."},{"Start":"02:48.175 ","End":"02:51.222","Text":"The movement achieved by contraction of muscles,"},{"Start":"02:51.222 ","End":"02:53.560","Text":"there still are muscles in these things,"},{"Start":"02:53.560 ","End":"02:58.990","Text":"and what they do is they change the way the fluid moves around inside."},{"Start":"02:58.990 ","End":"03:03.259","Text":"The muscle contraction changes the shape of the organism,"},{"Start":"03:03.259 ","End":"03:05.870","Text":"pushing the fluid back and forth."},{"Start":"03:05.870 ","End":"03:12.110","Text":"For instance, the earthworm moves with these waves, by peristaltic waves,"},{"Start":"03:12.110 ","End":"03:19.190","Text":"which shorten and lengthen the body and therefore it can move forward or backward."},{"Start":"03:19.190 ","End":"03:22.970","Text":"The hydrostatic skeleton moves the organism,"},{"Start":"03:22.970 ","End":"03:29.105","Text":"but it\u0027s really not very efficient for terrestrial animals."},{"Start":"03:29.105 ","End":"03:33.470","Text":"Let\u0027s now move on to the exoskeleton."},{"Start":"03:33.470 ","End":"03:37.595","Text":"Remember that\u0027s the skeleton which is on the outside of an organism,"},{"Start":"03:37.595 ","End":"03:39.530","Text":"and we saw shelves, for instance,"},{"Start":"03:39.530 ","End":"03:43.370","Text":"of snails, but there are other kinds of exoskeletons,"},{"Start":"03:43.370 ","End":"03:45.290","Text":"for instance, in arthropods,"},{"Start":"03:45.290 ","End":"03:47.015","Text":"insects, and things of that sort."},{"Start":"03:47.015 ","End":"03:49.340","Text":"What does it do? This exoskeleton, well,"},{"Start":"03:49.340 ","End":"03:54.259","Text":"provides defense against predators because it\u0027s on the outside,"},{"Start":"03:54.259 ","End":"03:56.060","Text":"it supports the body, of course,"},{"Start":"03:56.060 ","End":"04:00.020","Text":"and it also allows for movement because there are"},{"Start":"04:00.020 ","End":"04:04.520","Text":"muscles that are attached to different parts of the exoskeleton,"},{"Start":"04:04.520 ","End":"04:11.665","Text":"and the contraction of those muscles can then move different parts of the body."},{"Start":"04:11.665 ","End":"04:17.660","Text":"As with vertebrates, these muscles cross a joint."},{"Start":"04:17.660 ","End":"04:24.570","Text":"We\u0027ll have joints in exoskeleton-served organisms as well."},{"Start":"04:24.570 ","End":"04:27.995","Text":"Arthropods like insects, spiders, crustaceans,"},{"Start":"04:27.995 ","End":"04:32.405","Text":"and whatnot have these exoskeletons as we mentioned."},{"Start":"04:32.405 ","End":"04:35.660","Text":"Also, mollusks will have these."},{"Start":"04:35.660 ","End":"04:37.830","Text":"For instance, crabs."},{"Start":"04:37.830 ","End":"04:42.170","Text":"Let\u0027s look at the exoskeleton in more detail."},{"Start":"04:42.170 ","End":"04:45.800","Text":"It\u0027s composed of a thin outer layer,"},{"Start":"04:45.800 ","End":"04:54.140","Text":"which is called an epicuticle and a thick inner layer, that is chitin."},{"Start":"04:54.140 ","End":"04:55.955","Text":"Has a protein called chitin,"},{"Start":"04:55.955 ","End":"04:58.220","Text":"which is called the procuticle."},{"Start":"04:58.220 ","End":"04:59.990","Text":"You can see here for instance,"},{"Start":"04:59.990 ","End":"05:04.925","Text":"that we have the epicuticle and we have the procuticle,"},{"Start":"05:04.925 ","End":"05:08.730","Text":"which is composed of different layers itself,"},{"Start":"05:08.730 ","End":"05:11.855","Text":"and there\u0027ll be a basement membrane under that."},{"Start":"05:11.855 ","End":"05:19.265","Text":"There can be glands and there can be various kinds of protrusions through this cuticle."},{"Start":"05:19.265 ","End":"05:24.230","Text":"Now let\u0027s have a look and see what this chitin layer is."},{"Start":"05:24.230 ","End":"05:31.775","Text":"Chitin actually is not a protein but it\u0027s a strong flexible polysaccharide."},{"Start":"05:31.775 ","End":"05:33.050","Text":"It\u0027s a derivative of glucose,"},{"Start":"05:33.050 ","End":"05:35.600","Text":"of course as many polysaccharides are,"},{"Start":"05:35.600 ","End":"05:40.610","Text":"and it\u0027s secreted by this epidermal layer that we saw before."},{"Start":"05:40.610 ","End":"05:47.285","Text":"You can see these various organisms that have this chitin exoskeleton,"},{"Start":"05:47.285 ","End":"05:50.945","Text":"whereas other organisms can have"},{"Start":"05:50.945 ","End":"05:58.175","Text":"a much stiffer exoskeleton that is formed with calcium carbonate,"},{"Start":"05:58.175 ","End":"06:01.640","Text":"for instance, snails or various mollusks."},{"Start":"06:01.640 ","End":"06:09.405","Text":"That\u0027s a calcium carbonate exoskeleton as opposed to a chitin exoskeleton."},{"Start":"06:09.405 ","End":"06:13.280","Text":"Because the exoskeleton is acellular,"},{"Start":"06:13.280 ","End":"06:15.320","Text":"in other words, it doesn\u0027t have cells in it,"},{"Start":"06:15.320 ","End":"06:17.480","Text":"in order for the animals to grow,"},{"Start":"06:17.480 ","End":"06:20.330","Text":"they have to shed this exoskeleton,"},{"Start":"06:20.330 ","End":"06:25.710","Text":"and so we\u0027ll see there is shedding of this exoskeleton."}],"ID":30248},{"Watched":false,"Name":"The Endoskeleton - Skull","Duration":"9m 22s","ChapterTopicVideoID":28734,"CourseChapterTopicPlaylistID":286919,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.235","Text":"Now we\u0027re continuing with the discussion of the different types of skeletal systems,"},{"Start":"00:06.235 ","End":"00:10.380","Text":"and we\u0027re going to be looking at the endoskeleton."},{"Start":"00:10.380 ","End":"00:12.000","Text":"\"Endo\" means inside,"},{"Start":"00:12.000 ","End":"00:15.765","Text":"so it\u0027s going to be what we\u0027re really familiar with,"},{"Start":"00:15.765 ","End":"00:18.315","Text":"as a skeleton,"},{"Start":"00:18.315 ","End":"00:20.100","Text":"in other words, bones."},{"Start":"00:20.100 ","End":"00:24.885","Text":"We\u0027re going to be looking and seeing how 1 bone is connected to the other bone,"},{"Start":"00:24.885 ","End":"00:29.730","Text":"much like the song that such and such is connected to the suction such bone."},{"Start":"00:29.730 ","End":"00:35.030","Text":"The bones consist of hard mineralized structures that are located within,"},{"Start":"00:35.030 ","End":"00:40.360","Text":"not outside, but located within the soft tissue of organisms."},{"Start":"00:40.360 ","End":"00:44.700","Text":"Of course, that provides support for the body,"},{"Start":"00:44.700 ","End":"00:49.145","Text":"and it allows movement through the contraction of muscles."},{"Start":"00:49.145 ","End":"00:52.350","Text":"It protects internal organs."},{"Start":"00:52.350 ","End":"00:53.909","Text":"If we look, for instance, at the ribcage,"},{"Start":"00:53.909 ","End":"00:55.410","Text":"it protects what\u0027s inside."},{"Start":"00:55.410 ","End":"00:59.040","Text":"Our skull protects what\u0027s inside."},{"Start":"00:59.040 ","End":"01:01.695","Text":"It\u0027s found in all organisms,"},{"Start":"01:01.695 ","End":"01:05.218","Text":"even in things like sponges."},{"Start":"01:05.218 ","End":"01:07.400","Text":"It\u0027s called spicules."},{"Start":"01:07.400 ","End":"01:13.300","Text":"Those are these things that are actually within the sponge,"},{"Start":"01:13.300 ","End":"01:15.320","Text":"different shaped kinds of things,"},{"Start":"01:15.320 ","End":"01:17.390","Text":"these spicules, but of course,"},{"Start":"01:17.390 ","End":"01:24.980","Text":"we\u0027re going to be concerned primarily with bones that are found in mammals like us."},{"Start":"01:24.980 ","End":"01:29.029","Text":"Of course, vertebrates\u0027 bones are composed of tissues."},{"Start":"01:29.029 ","End":"01:32.060","Text":"In other words, these bones are alive,"},{"Start":"01:32.060 ","End":"01:36.945","Text":"whereas the sponges don\u0027t really have real different tissues."},{"Start":"01:36.945 ","End":"01:41.029","Text":"They have different parts of the sponge,"},{"Start":"01:41.029 ","End":"01:45.580","Text":"but not necessarily as each of them alive."},{"Start":"01:45.580 ","End":"01:50.420","Text":"Let\u0027s see what these bones are all about."},{"Start":"01:50.420 ","End":"01:58.330","Text":"The bones store minerals and lipids in addition to providing what we saw before."},{"Start":"01:58.330 ","End":"02:02.850","Text":"Interestingly, there is bone marrow on the inside of these bones,"},{"Start":"02:02.850 ","End":"02:04.055","Text":"some of them at least,"},{"Start":"02:04.055 ","End":"02:09.575","Text":"and those are going to be places where there\u0027s a manufacturer of blood cells."},{"Start":"02:09.575 ","End":"02:16.190","Text":"Now let\u0027s look at specific different bones and different structures."},{"Start":"02:16.190 ","End":"02:19.715","Text":"We\u0027ll start with the axial skeleton."},{"Start":"02:19.715 ","End":"02:25.440","Text":"You can see there\u0027s an axis here that\u0027s going to include the skull,"},{"Start":"02:25.440 ","End":"02:27.345","Text":"and the vertebra,"},{"Start":"02:27.345 ","End":"02:32.915","Text":"and we\u0027re going to have the ribcage, for instance."},{"Start":"02:32.915 ","End":"02:34.790","Text":"There is going to be,"},{"Start":"02:34.790 ","End":"02:41.675","Text":"in addition to that, an appendicular skeleton."},{"Start":"02:41.675 ","End":"02:43.730","Text":"What\u0027s this appendicular skeleton?"},{"Start":"02:43.730 ","End":"02:45.110","Text":"These are the appendages,"},{"Start":"02:45.110 ","End":"02:48.615","Text":"our arms and our legs."},{"Start":"02:48.615 ","End":"02:51.710","Text":"They consist of the arms and legs,"},{"Start":"02:51.710 ","End":"02:54.005","Text":"themselves, but also various girdle."},{"Start":"02:54.005 ","End":"02:57.530","Text":"You\u0027ll see that there is this girdle over here in our pelvis,"},{"Start":"02:57.530 ","End":"03:03.330","Text":"and there\u0027s another girdle over here which is our shoulder blades."},{"Start":"03:03.880 ","End":"03:06.965","Text":"There\u0027s the pectoral girdle,"},{"Start":"03:06.965 ","End":"03:09.635","Text":"that\u0027s the one that is up on top,"},{"Start":"03:09.635 ","End":"03:13.730","Text":"and there is the pelvic girdle which is the one underneath."},{"Start":"03:13.730 ","End":"03:15.560","Text":"Now there are lots of different bones."},{"Start":"03:15.560 ","End":"03:17.720","Text":"There are about 270 bones at birth,"},{"Start":"03:17.720 ","End":"03:19.430","Text":"but some of them fuse together,"},{"Start":"03:19.430 ","End":"03:21.920","Text":"so when we count at the end of the day,"},{"Start":"03:21.920 ","End":"03:25.480","Text":"we\u0027ve got about 206 bones by adulthood."},{"Start":"03:25.480 ","End":"03:29.920","Text":"Let\u0027s look now at the axial skeleton in more detail,"},{"Start":"03:29.920 ","End":"03:35.165","Text":"and we\u0027ll see that there are about 80 bones in the human."},{"Start":"03:35.165 ","End":"03:38.695","Text":"These include the skull,"},{"Start":"03:38.695 ","End":"03:42.240","Text":"there are these ossicles in the inner ear,"},{"Start":"03:42.240 ","End":"03:45.343","Text":"there\u0027s another bone that we\u0027ll see later called the hyoid bone,"},{"Start":"03:45.343 ","End":"03:46.805","Text":"it\u0027s free floating,"},{"Start":"03:46.805 ","End":"03:49.495","Text":"and there\u0027s the ribcage."},{"Start":"03:49.495 ","End":"03:52.430","Text":"Of course, these are included and the main functions"},{"Start":"03:52.430 ","End":"03:55.160","Text":"of all of these are to provide support and protection for the brain,"},{"Start":"03:55.160 ","End":"03:57.026","Text":"as we mentioned before, and the spinal cord"},{"Start":"03:57.026 ","End":"03:59.690","Text":"because inside the spinal cord, in the middle,"},{"Start":"03:59.690 ","End":"04:03.675","Text":"there are these nerves that innervate the lower parts of our body, of course,"},{"Start":"04:03.675 ","End":"04:07.040","Text":"and it also provides support and protection for"},{"Start":"04:07.040 ","End":"04:10.925","Text":"the organs that are in the central body cavity."},{"Start":"04:10.925 ","End":"04:17.250","Text":"They also provide attachment surfaces for muscles that move the head,"},{"Start":"04:17.250 ","End":"04:20.125","Text":"the neck, and the trunk."},{"Start":"04:20.125 ","End":"04:27.995","Text":"Now they also have functions in movement that are important for respiration."},{"Start":"04:27.995 ","End":"04:30.805","Text":"For instance, your ribcage moves up and down,"},{"Start":"04:30.805 ","End":"04:34.160","Text":"and it also stabilizes parts of"},{"Start":"04:34.160 ","End":"04:40.070","Text":"the appendicular skeleton that\u0027s going to support the arms and legs."},{"Start":"04:40.070 ","End":"04:42.365","Text":"Let\u0027s now look at more detail,"},{"Start":"04:42.365 ","End":"04:45.275","Text":"and let\u0027s concentrate on the skull."},{"Start":"04:45.275 ","End":"04:49.590","Text":"The skull consists of 22 different bones that,"},{"Start":"04:49.590 ","End":"04:53.045","Text":"as you can see, fuse together after birth."},{"Start":"04:53.045 ","End":"04:56.529","Text":"The cranium is this upper part."},{"Start":"04:56.529 ","End":"05:00.945","Text":"There is the facial skeleton that\u0027s in our face."},{"Start":"05:00.945 ","End":"05:03.735","Text":"The main function of these bones, of course,"},{"Start":"05:03.735 ","End":"05:07.250","Text":"are to provide protection for the brain,"},{"Start":"05:07.250 ","End":"05:10.370","Text":"which is inside, and also to provide an orbit,"},{"Start":"05:10.370 ","End":"05:15.305","Text":"that is an area in which the eyes are positioned."},{"Start":"05:15.305 ","End":"05:17.990","Text":"The skull provides an anchor for"},{"Start":"05:17.990 ","End":"05:21.500","Text":"the tendinous and muscular attachments of the muscles of the skull and face."},{"Start":"05:21.500 ","End":"05:23.455","Text":"So we\u0027ve got muscles,"},{"Start":"05:23.455 ","End":"05:26.510","Text":"lots of detailed muscles that are, for instance,"},{"Start":"05:26.510 ","End":"05:32.540","Text":"in our face, and the skull provides an attachment for these things."},{"Start":"05:32.540 ","End":"05:34.655","Text":"Let\u0027s delve deeper."},{"Start":"05:34.655 ","End":"05:37.115","Text":"So let\u0027s look at the cranial bones."},{"Start":"05:37.115 ","End":"05:40.405","Text":"The 8 bones are frontal bone,"},{"Start":"05:40.405 ","End":"05:43.215","Text":"there are 2 parietal bones,"},{"Start":"05:43.215 ","End":"05:47.805","Text":"1 on each side, 2 temporal bones, 1 on each side,"},{"Start":"05:47.805 ","End":"05:50.235","Text":"and occipital bone,"},{"Start":"05:50.235 ","End":"05:51.885","Text":"that\u0027s in the back,"},{"Start":"05:51.885 ","End":"06:00.590","Text":"and the ethmoid bone which is a small bone that\u0027s found in the front behind the nose."},{"Start":"06:00.590 ","End":"06:05.240","Text":"Now these bones form the cranial cavity which encloses"},{"Start":"06:05.240 ","End":"06:07.040","Text":"the brain and serves as an attachment site for"},{"Start":"06:07.040 ","End":"06:10.835","Text":"the various muscles that we\u0027ve described briefly before."},{"Start":"06:10.835 ","End":"06:16.875","Text":"Although each of these bones develop separately during embryogenesis,"},{"Start":"06:16.875 ","End":"06:18.980","Text":"in the adult, they\u0027re fused together,"},{"Start":"06:18.980 ","End":"06:22.790","Text":"and they make this very tight structure in which"},{"Start":"06:22.790 ","End":"06:27.610","Text":"the bones don\u0027t move with respect to one another."},{"Start":"06:27.610 ","End":"06:32.570","Text":"Now in the ear, you remember when we discussed the way we hear,"},{"Start":"06:32.570 ","End":"06:35.555","Text":"there are also some very small bones."},{"Start":"06:35.555 ","End":"06:38.150","Text":"There\u0027s the malleus, the incus,"},{"Start":"06:38.150 ","End":"06:40.700","Text":"and the stapes that are in the inner ear."},{"Start":"06:40.700 ","End":"06:44.165","Text":"Each of them move a little bit to amplify"},{"Start":"06:44.165 ","End":"06:49.650","Text":"the sounds that comes into our ear and strikes the tympanic membrane."},{"Start":"06:49.650 ","End":"06:51.980","Text":"Here are some of more very small bones,"},{"Start":"06:51.980 ","End":"06:54.860","Text":"in the body they\u0027re actually the smallest bones in the body,"},{"Start":"06:54.860 ","End":"06:56.905","Text":"and they\u0027re located in the middle ear,"},{"Start":"06:56.905 ","End":"07:01.880","Text":"and increase the volume of the sounds that come into"},{"Start":"07:01.880 ","End":"07:08.945","Text":"our ear so that they can then be registered in our nervous system."},{"Start":"07:08.945 ","End":"07:14.670","Text":"Interestingly, the 3 auditory ossicles are unique to mammals."},{"Start":"07:14.670 ","End":"07:19.255","Text":"Other organisms that are not mammals don\u0027t have them."},{"Start":"07:19.255 ","End":"07:23.925","Text":"Now let\u0027s look at the front of the skull."},{"Start":"07:23.925 ","End":"07:31.180","Text":"We\u0027ll see that there\u0027s a facial skeleton consisting of 14 bones that are the nasal,"},{"Start":"07:31.180 ","End":"07:38.205","Text":"the maxillary, that\u0027s above the teeth,"},{"Start":"07:38.205 ","End":"07:42.250","Text":"there\u0027s the zygomatic, palatine,"},{"Start":"07:43.000 ","End":"07:49.000","Text":"that\u0027s on the side of our face and side the eyes,"},{"Start":"07:49.000 ","End":"07:53.040","Text":"lacrimal means things that have to do with the eyes,"},{"Start":"07:53.040 ","End":"07:55.845","Text":"so that\u0027s where we see these,"},{"Start":"07:55.845 ","End":"07:59.925","Text":"and the inferior nasal conchae, and the mandible."},{"Start":"07:59.925 ","End":"08:02.340","Text":"Again, these have to do with nose,"},{"Start":"08:02.340 ","End":"08:05.840","Text":"and the mandible is this very large bone which is on the bottom that"},{"Start":"08:05.840 ","End":"08:10.045","Text":"moves to which are attached to the lower teeth."},{"Start":"08:10.045 ","End":"08:13.085","Text":"Now all of these bones actually are paired on"},{"Start":"08:13.085 ","End":"08:17.540","Text":"each side of the face except for the mandible which goes all the way across,"},{"Start":"08:17.540 ","End":"08:23.000","Text":"and the vomer which is part of the nose."},{"Start":"08:23.000 ","End":"08:25.520","Text":"These form the face. They provide cavities"},{"Start":"08:25.520 ","End":"08:27.710","Text":"for the sense organs of the eyes, mouth, and nose,"},{"Start":"08:27.710 ","End":"08:32.480","Text":"and they protect the entrances to the digestive and respiratory tracts,"},{"Start":"08:32.480 ","End":"08:36.230","Text":"and of course, they\u0027re attachment points for the facial muscles,"},{"Start":"08:36.230 ","End":"08:38.745","Text":"as we\u0027ve discussed before."},{"Start":"08:38.745 ","End":"08:43.380","Text":"Lastly, let\u0027s look at the hyoid bone."},{"Start":"08:43.380 ","End":"08:45.125","Text":"It\u0027s not really attached to anything."},{"Start":"08:45.125 ","End":"08:48.340","Text":"It is a solitary bone that lies"},{"Start":"08:48.340 ","End":"08:52.060","Text":"below the mandible that we see here in the front of the neck,"},{"Start":"08:52.060 ","End":"08:55.944","Text":"and it\u0027s considered a component of the axial skeleton,"},{"Start":"08:55.944 ","End":"08:59.226","Text":"but it\u0027s not really found in the skull."},{"Start":"08:59.226 ","End":"09:04.345","Text":"It moves as a base for the tongue that is above it,"},{"Start":"09:04.345 ","End":"09:07.540","Text":"and it also holds up the larynx,"},{"Start":"09:07.540 ","End":"09:09.975","Text":"which is the voice box,"},{"Start":"09:09.975 ","End":"09:13.115","Text":"that is below it."},{"Start":"09:13.115 ","End":"09:18.130","Text":"It is the only bone in humans that does not connect,"},{"Start":"09:18.130 ","End":"09:19.555","Text":"does not articulate,"},{"Start":"09:19.555 ","End":"09:22.400","Text":"with any other bone."}],"ID":30249},{"Watched":false,"Name":"The Endoskeleton - Rib Cage","Duration":"8m ","ChapterTopicVideoID":28733,"CourseChapterTopicPlaylistID":286919,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.195","Text":"I see that you\u0027re back to continue our discussion of the types of skeletal muscles."},{"Start":"00:06.195 ","End":"00:09.524","Text":"We were talking about the endoskeleton,"},{"Start":"00:09.524 ","End":"00:15.720","Text":"and we\u0027ve been looking primarily in the last video at the skull."},{"Start":"00:15.720 ","End":"00:19.859","Text":"So let\u0027s continue with that discussion and discuss the mandible,"},{"Start":"00:19.859 ","End":"00:25.410","Text":"which is the bone to which our lower teeth are attached and which moves up and down."},{"Start":"00:25.410 ","End":"00:27.350","Text":"It\u0027s the largest bone in the skull,"},{"Start":"00:27.350 ","End":"00:30.210","Text":"and it forms the lower jaw."},{"Start":"00:30.210 ","End":"00:32.820","Text":"It articulates, it means that connects,"},{"Start":"00:32.820 ","End":"00:38.028","Text":"with the base of the skull and controls the opening to the airway,"},{"Start":"00:38.028 ","End":"00:39.375","Text":"that\u0027s where we breathe,"},{"Start":"00:39.375 ","End":"00:41.760","Text":"and also to the gut."},{"Start":"00:41.760 ","End":"00:49.050","Text":"The food goes down through the teeth and so does air that goes into our mouth."},{"Start":"00:49.050 ","End":"00:53.330","Text":"In animals with teeth, the mandible brings the surfaces of the teeth in contact with"},{"Start":"00:53.330 ","End":"00:59.900","Text":"the maxillary teeth that are on top so that they can chew."},{"Start":"00:59.900 ","End":"01:04.895","Text":"Now let\u0027s move down a bit and have a look at the vertebral column,"},{"Start":"01:04.895 ","End":"01:07.085","Text":"or the spinal column."},{"Start":"01:07.085 ","End":"01:10.070","Text":"Of course, this surrounds and protects the spinal cord,"},{"Start":"01:10.070 ","End":"01:14.350","Text":"that\u0027s the nerve that goes down through our spine."},{"Start":"01:14.350 ","End":"01:16.710","Text":"It also supports the head and acts as"},{"Start":"01:16.710 ","End":"01:20.600","Text":"an attachment point for the ribs and the muscles of the back,"},{"Start":"01:20.600 ","End":"01:22.790","Text":"and neck, and so on."},{"Start":"01:22.790 ","End":"01:27.650","Text":"Originally, it develops as a series of 33 vertebrae,"},{"Start":"01:27.650 ","End":"01:32.840","Text":"but then it\u0027s reduced to 24 by fusion,"},{"Start":"01:32.840 ","End":"01:37.265","Text":"as we\u0027ve seen is the case before, in the skull."},{"Start":"01:37.265 ","End":"01:39.200","Text":"Now let\u0027s look at the different parts."},{"Start":"01:39.200 ","End":"01:41.720","Text":"First of all, there\u0027s the sacrum,"},{"Start":"01:41.720 ","End":"01:46.040","Text":"the sacral vertebrae, which are shown down here,"},{"Start":"01:46.040 ","End":"01:48.950","Text":"they\u0027re at the bottom of the vertebrae."},{"Start":"01:48.950 ","End":"01:52.490","Text":"There were 5 of them, and they fuse into 1 in adults."},{"Start":"01:52.490 ","End":"01:56.110","Text":"There\u0027s the coccyx, which is just below it."},{"Start":"01:56.110 ","End":"02:01.385","Text":"There are typically 3 or 5 vertebrae there that also fuse into 1."},{"Start":"02:01.385 ","End":"02:03.500","Text":"At age 70, roughly,"},{"Start":"02:03.500 ","End":"02:07.910","Text":"all of these fuse together, creating 1 bone."},{"Start":"02:07.910 ","End":"02:11.150","Text":"Let\u0027s look at other vertebrae."},{"Start":"02:11.150 ","End":"02:13.310","Text":"The cervical vertebrae,"},{"Start":"02:13.310 ","End":"02:14.885","Text":"there are 7 of them."},{"Start":"02:14.885 ","End":"02:18.965","Text":"There are 12 thoracic vertebrae."},{"Start":"02:18.965 ","End":"02:22.600","Text":"There are 5 lumbar vertebrae."},{"Start":"02:22.600 ","End":"02:31.535","Text":"Almost all mammals have the 7 cervical vertebrae that I mentioned above,"},{"Start":"02:31.535 ","End":"02:33.455","Text":"regardless of body size."},{"Start":"02:33.455 ","End":"02:36.345","Text":"But there are a few exceptions."},{"Start":"02:36.345 ","End":"02:38.490","Text":"Manatees, for instance,"},{"Start":"02:38.490 ","End":"02:40.830","Text":"the 2-toed sloths,"},{"Start":"02:40.830 ","End":"02:45.125","Text":"and 3-toed sloths have different numbers."},{"Start":"02:45.125 ","End":"02:51.350","Text":"But in general, we have 7 cervical vertebrae."},{"Start":"02:51.350 ","End":"02:56.300","Text":"Now, each of the vertebra has a large hole in the center."},{"Start":"02:56.300 ","End":"02:58.250","Text":"Here\u0027s 1 vertebra,"},{"Start":"02:58.250 ","End":"03:00.035","Text":"and you can see there\u0027s a hole in the center,"},{"Start":"03:00.035 ","End":"03:03.125","Text":"through that, the spinal cord passes."},{"Start":"03:03.125 ","End":"03:05.365","Text":"Also there\u0027s a notch on"},{"Start":"03:05.365 ","End":"03:11.540","Text":"the side of each of them through which the spinal nerves can exit from"},{"Start":"03:11.540 ","End":"03:14.569","Text":"the spinal cord so that they can innervate"},{"Start":"03:14.569 ","End":"03:22.190","Text":"the areas in the limbs and in the other parts of the thorax."},{"Start":"03:22.190 ","End":"03:25.025","Text":"Now, the spine is not straight up and down."},{"Start":"03:25.025 ","End":"03:28.955","Text":"It has curves as you can see in this picture."},{"Start":"03:28.955 ","End":"03:35.075","Text":"The adult vertebral column has 4 curvatures along its length."},{"Start":"03:35.075 ","End":"03:39.665","Text":"The cervical curvature, the thoracic curvature,"},{"Start":"03:39.665 ","End":"03:47.225","Text":"the lumbar curvature, and the sacral curvature as we move down the spine."},{"Start":"03:47.225 ","End":"03:54.215","Text":"The thoracic and sacral curvatures curve inwards relative to the front of the body."},{"Start":"03:54.215 ","End":"04:00.690","Text":"Whereas the cervical and the lumbar curvatures curve outwards relative to the body."},{"Start":"04:00.690 ","End":"04:06.050","Text":"These curvatures of course increase the vertebral column\u0027s strength,"},{"Start":"04:06.050 ","End":"04:08.945","Text":"its flexibility, its ability to absorb shock."},{"Start":"04:08.945 ","End":"04:11.870","Text":"For instance, if there is some load on the spine,"},{"Start":"04:11.870 ","End":"04:13.350","Text":"then it doesn\u0027t just crack,"},{"Start":"04:13.350 ","End":"04:17.570","Text":"it can bend a little bit and accommodate all that extra weight."},{"Start":"04:17.570 ","End":"04:24.365","Text":"Now, in between the various vertebrae are intervertebral discs."},{"Start":"04:24.365 ","End":"04:27.065","Text":"I\u0027m sure you\u0027ve heard of something called a slipped disc."},{"Start":"04:27.065 ","End":"04:28.180","Text":"That\u0027s what we\u0027re talking about."},{"Start":"04:28.180 ","End":"04:31.730","Text":"There are these discs that are between the bone,"},{"Start":"04:31.730 ","End":"04:36.545","Text":"and they are sometimes called annulus fibrosus."},{"Start":"04:36.545 ","End":"04:41.240","Text":"It\u0027s a tough outer covering of some cartilage that provides support."},{"Start":"04:41.240 ","End":"04:46.295","Text":"Then inside, there\u0027s this soft jelly-like center that provides the cushioning."},{"Start":"04:46.295 ","End":"04:49.280","Text":"Each disc lies between the adjacent vertebrae,"},{"Start":"04:49.280 ","End":"04:52.890","Text":"as we said before, from the top to the bottom."},{"Start":"04:52.890 ","End":"04:56.600","Text":"So it forms joints that allow some movement and also"},{"Start":"04:56.600 ","End":"05:01.880","Text":"cushioning that can be important when we\u0027re walking or we\u0027re running."},{"Start":"05:01.880 ","End":"05:05.975","Text":"The nucleus pulposus hardens and becomes"},{"Start":"05:05.975 ","End":"05:10.680","Text":"less elastic with age and that reduces the ability to absorb shocks."},{"Start":"05:10.680 ","End":"05:15.090","Text":"That\u0027s 1 of the features of aging."},{"Start":"05:15.090 ","End":"05:19.280","Text":"Now let\u0027s look at the thoracic cage,"},{"Start":"05:19.280 ","End":"05:21.965","Text":"or what\u0027s called the ribcage."},{"Start":"05:21.965 ","End":"05:27.710","Text":"The skeleton consists of the ribs themselves, of the sternum,"},{"Start":"05:27.710 ","End":"05:30.080","Text":"which is right in the center,"},{"Start":"05:30.080 ","End":"05:33.920","Text":"and the costal cartilages."},{"Start":"05:33.920 ","End":"05:40.415","Text":"The costal cartilages are cartilage that attach the ribs to the sternum."},{"Start":"05:40.415 ","End":"05:44.465","Text":"This, of course, encloses and protects the organs"},{"Start":"05:44.465 ","End":"05:49.370","Text":"inside the thoracic cavity that include the heart and the lungs,"},{"Start":"05:49.370 ","End":"05:51.250","Text":"very important that they be protected."},{"Start":"05:51.250 ","End":"05:53.810","Text":"It provides support for the shoulder girdles"},{"Start":"05:53.810 ","End":"05:56.990","Text":"and the upper limbs and serves as the attachment point for the diaphragm,"},{"Start":"05:56.990 ","End":"05:59.045","Text":"which is underneath,"},{"Start":"05:59.045 ","End":"06:00.870","Text":"over here that helps us breathe,"},{"Start":"06:00.870 ","End":"06:03.628","Text":"it pushes up and down and moves our lungs,"},{"Start":"06:03.628 ","End":"06:05.480","Text":"the muscles of the back,"},{"Start":"06:05.480 ","End":"06:06.830","Text":"they\u0027ll be on top, and the chest,"},{"Start":"06:06.830 ","End":"06:08.390","Text":"and neck, and shoulders."},{"Start":"06:08.390 ","End":"06:13.790","Text":"These ribs can help change the volume of"},{"Start":"06:13.790 ","End":"06:18.785","Text":"this area with the muscles around it that enable the breathing,"},{"Start":"06:18.785 ","End":"06:21.415","Text":"actually, cause really the breathing."},{"Start":"06:21.415 ","End":"06:24.965","Text":"Now let\u0027s look at the sternum in more detail."},{"Start":"06:24.965 ","End":"06:30.800","Text":"The sternum is this long flat bone that\u0027s at the interior of the chest,"},{"Start":"06:30.800 ","End":"06:35.570","Text":"and it\u0027s formed from 3 bones that fuse in the adult."},{"Start":"06:35.570 ","End":"06:37.550","Text":"It connects, as we said before,"},{"Start":"06:37.550 ","End":"06:42.820","Text":"the costal cartilages with the anterior ribcage."},{"Start":"06:42.820 ","End":"06:48.200","Text":"It also helps in protecting the torso organs because the cartilage has"},{"Start":"06:48.200 ","End":"06:54.065","Text":"some flexibility and doesn\u0027t allow penetration of hard objects."},{"Start":"06:54.065 ","End":"06:56.045","Text":"The ribs, themselves,"},{"Start":"06:56.045 ","End":"06:57.365","Text":"there are 12 of them."},{"Start":"06:57.365 ","End":"06:59.240","Text":"They are curved, and they attach to"},{"Start":"06:59.240 ","End":"07:03.275","Text":"the thoracic vertebrae that are in the back and in the front,"},{"Start":"07:03.275 ","End":"07:06.409","Text":"form the ribcage,"},{"Start":"07:06.409 ","End":"07:08.110","Text":"connecting to the sternum."},{"Start":"07:08.110 ","End":"07:12.000","Text":"Their function also is to aid with breathing,"},{"Start":"07:12.000 ","End":"07:15.860","Text":"with respiration, and for protection of what\u0027s inside."},{"Start":"07:15.860 ","End":"07:21.495","Text":"We divide the ribs into true ribs, that are the bone,"},{"Start":"07:21.495 ","End":"07:30.770","Text":"and the false ribs that are at the bottom here that don\u0027t attach directly to the sternum."},{"Start":"07:30.770 ","End":"07:36.235","Text":"They do it indirectly through these connect pieces of cartilage,"},{"Start":"07:36.235 ","End":"07:38.990","Text":"somewhat of an artificial definition,"},{"Start":"07:38.990 ","End":"07:40.805","Text":"but it\u0027s what we have."},{"Start":"07:40.805 ","End":"07:46.880","Text":"Pairs 11 and 12 are what are called free floating ribs because they don\u0027t connect here."},{"Start":"07:46.880 ","End":"07:48.800","Text":"There\u0027s 2 of them. They\u0027re 11 and 12."},{"Start":"07:48.800 ","End":"07:52.805","Text":"They don\u0027t connect at all to the sternum."},{"Start":"07:52.805 ","End":"07:58.380","Text":"The costal cartilage is what does this connection."}],"ID":30250},{"Watched":false,"Name":"The Endoskeleton - Arms and Hands","Duration":"4m 48s","ChapterTopicVideoID":28736,"CourseChapterTopicPlaylistID":286919,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.400","Text":"Let\u0027s move on with our discussion of"},{"Start":"00:03.400 ","End":"00:08.565","Text":"the skeletal systems by looking at the appendicular skeleton,"},{"Start":"00:08.565 ","End":"00:11.710","Text":"the appendages, that\u0027s our arms and legs,"},{"Start":"00:11.710 ","End":"00:16.360","Text":"go into more detail about which bones there are in each of those appendices."},{"Start":"00:16.360 ","End":"00:19.990","Text":"There are lots of these bones,"},{"Start":"00:19.990 ","End":"00:21.805","Text":"126 or so of them,"},{"Start":"00:21.805 ","End":"00:23.320","Text":"and there, of course,"},{"Start":"00:23.320 ","End":"00:25.540","Text":"are the upper and lower limbs."},{"Start":"00:25.540 ","End":"00:27.130","Text":"On the upper one,"},{"Start":"00:27.130 ","End":"00:29.990","Text":"we have the shoulder girdle,"},{"Start":"00:29.990 ","End":"00:35.775","Text":"sometimes we call this the pectoral girdle as well."},{"Start":"00:35.775 ","End":"00:37.885","Text":"It\u0027s on top of the shoulder blades."},{"Start":"00:37.885 ","End":"00:40.240","Text":"We have the pelvic girdle."},{"Start":"00:40.240 ","End":"00:45.360","Text":"These are these flat bones both on the top and the bottom to which attach,"},{"Start":"00:45.360 ","End":"00:48.380","Text":"on the case of the pelvic girdle, the lower limbs,"},{"Start":"00:48.380 ","End":"00:52.790","Text":"and in the case of the shoulder girdle, the upper limbs."},{"Start":"00:52.790 ","End":"00:56.820","Text":"If we look at the pectoral girdle in more detail,"},{"Start":"00:56.820 ","End":"00:58.140","Text":"here it\u0027s shown in blue,"},{"Start":"00:58.140 ","End":"01:04.370","Text":"we can see that it provides points of attachment to the upper limbs that we can see up"},{"Start":"01:04.370 ","End":"01:10.640","Text":"here and to the axial skeleton, to our vertebra."},{"Start":"01:10.640 ","End":"01:16.258","Text":"The human pectoral girdle then consists of a bone called the clavicle,"},{"Start":"01:16.258 ","End":"01:17.600","Text":"this one that goes across,"},{"Start":"01:17.600 ","End":"01:21.020","Text":"sometimes it\u0027s called the collarbone that\u0027s in the interior in the front of us,"},{"Start":"01:21.020 ","End":"01:26.400","Text":"and the scapula, that\u0027s the shoulder blade in the back, in the posterior."},{"Start":"01:26.400 ","End":"01:29.350","Text":"Some mammalian species such as dog and horse,"},{"Start":"01:29.350 ","End":"01:34.195","Text":"have only the scapula and they don\u0027t have the clavicle."},{"Start":"01:34.195 ","End":"01:36.470","Text":"The collarbone, the clavicles,"},{"Start":"01:36.470 ","End":"01:38.630","Text":"are S-shaped and they lie"},{"Start":"01:38.630 ","End":"01:41.780","Text":"horizontally across the front of the thorax and position the arms."},{"Start":"01:41.780 ","End":"01:44.030","Text":"We all can see them from the outside,"},{"Start":"01:44.030 ","End":"01:45.260","Text":"so we know what they are."},{"Start":"01:45.260 ","End":"01:48.575","Text":"Sometimes they\u0027re called a beauty bone."},{"Start":"01:48.575 ","End":"01:50.030","Text":"They\u0027re quite fragile."},{"Start":"01:50.030 ","End":"01:51.965","Text":"If you get hit on 1 of them,"},{"Start":"01:51.965 ","End":"01:55.520","Text":"you can get fractured [inaudible], fairly common fracture."},{"Start":"01:55.520 ","End":"01:57.410","Text":"It articulates, that is,"},{"Start":"01:57.410 ","End":"02:04.150","Text":"it contacts the sternum in the front and the scapula in the back."},{"Start":"02:04.150 ","End":"02:05.820","Text":"So the scapulae,"},{"Start":"02:05.820 ","End":"02:07.605","Text":"in plural here,"},{"Start":"02:07.605 ","End":"02:12.260","Text":"are the shoulder bone, it\u0027s that bone that\u0027s in the back that we saw before."},{"Start":"02:12.260 ","End":"02:14.150","Text":"It\u0027s flat, it\u0027s triangular,"},{"Start":"02:14.150 ","End":"02:18.883","Text":"and it supports the muscles that cross the shoulder,"},{"Start":"02:18.883 ","End":"02:23.030","Text":"and it\u0027s important for the function of the shoulder joint."},{"Start":"02:23.030 ","End":"02:26.180","Text":"Now, the spine of the scapula,"},{"Start":"02:26.180 ","End":"02:28.190","Text":"that\u0027s the top of it,"},{"Start":"02:28.190 ","End":"02:30.620","Text":"it\u0027s this ridge that runs across the back,"},{"Start":"02:30.620 ","End":"02:35.690","Text":"and it facilitates a broad area of attachment for muscles to the bone."},{"Start":"02:35.690 ","End":"02:41.610","Text":"Let\u0027s move on now to the upper limb to the arms,"},{"Start":"02:41.610 ","End":"02:47.465","Text":"and here we can see the bones that we just finished talking about."},{"Start":"02:47.465 ","End":"02:51.820","Text":"The arms here then contain about 30 bones,"},{"Start":"02:51.820 ","End":"02:58.565","Text":"and there\u0027s a single bone called the humerus which is at the top,"},{"Start":"02:58.565 ","End":"03:02.150","Text":"which is articulated to the ulna and the radius."},{"Start":"03:02.150 ","End":"03:05.280","Text":"They are down below. That\u0027s called the forearm, that area."},{"Start":"03:05.280 ","End":"03:06.710","Text":"Then there\u0027s the hand, of course,"},{"Start":"03:06.710 ","End":"03:09.350","Text":"which contains many different bones,"},{"Start":"03:09.350 ","End":"03:11.180","Text":"about 27 of them,"},{"Start":"03:11.180 ","End":"03:17.210","Text":"that are in different groups called phalanges, metacarpals, and carpels."},{"Start":"03:17.210 ","End":"03:20.870","Text":"Now, as we said,"},{"Start":"03:20.870 ","End":"03:24.920","Text":"an articulated point or a joint is where 2 bones come together."},{"Start":"03:24.920 ","End":"03:27.305","Text":"Interestingly, if you have a look at"},{"Start":"03:27.305 ","End":"03:31.130","Text":"the bones that are in the lower arm or in the forearm,"},{"Start":"03:31.130 ","End":"03:32.525","Text":"the ulna and the radius,"},{"Start":"03:32.525 ","End":"03:36.755","Text":"they can turn with respect to 1 another and that allows"},{"Start":"03:36.755 ","End":"03:41.030","Text":"us to turn our hands over, as you can see,"},{"Start":"03:41.030 ","End":"03:44.585","Text":"pronation or supination,"},{"Start":"03:44.585 ","End":"03:49.280","Text":"the way our hand is facing the humerus is"},{"Start":"03:49.280 ","End":"03:56.790","Text":"articulating with the scapula at the shoulder and the forearm at the elbow."},{"Start":"03:56.790 ","End":"03:59.135","Text":"The humerus connects up on top,"},{"Start":"03:59.135 ","End":"04:00.487","Text":"and at the bottom,"},{"Start":"04:00.487 ","End":"04:05.124","Text":"the forearm, it articulates with the radius and the ulna."},{"Start":"04:05.124 ","End":"04:11.220","Text":"Of course, it\u0027s really the ulna that articulates"},{"Start":"04:11.220 ","End":"04:16.950","Text":"with the carpal bones that are down in the hands over here."},{"Start":"04:16.950 ","End":"04:19.505","Text":"Now let\u0027s look at the hand in more detail."},{"Start":"04:19.505 ","End":"04:24.305","Text":"It contains 8 bones in the wrist and the carpal area,"},{"Start":"04:24.305 ","End":"04:27.605","Text":"5 bones in the metacarpal area,"},{"Start":"04:27.605 ","End":"04:29.719","Text":"that\u0027s in the palm of the hand,"},{"Start":"04:29.719 ","End":"04:33.860","Text":"and 14 bones of the digits of the fingers,"},{"Start":"04:33.860 ","End":"04:36.950","Text":"the phalanges, that are at the bottom."},{"Start":"04:36.950 ","End":"04:42.690","Text":"Each digit, each of these consists of 3 phalanges, 1,"},{"Start":"04:42.690 ","End":"04:44.485","Text":"2, 3,"},{"Start":"04:44.485 ","End":"04:45.980","Text":"except for the thumb,"},{"Start":"04:45.980 ","End":"04:49.700","Text":"which as you can see contains only 2."}],"ID":30251},{"Watched":false,"Name":"The Endoskeleton - Pelvis and Legs","Duration":"6m 32s","ChapterTopicVideoID":28732,"CourseChapterTopicPlaylistID":286919,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.580","Text":"Now we\u0027re going to continue our discussion by"},{"Start":"00:02.580 ","End":"00:06.630","Text":"moving down the body into this area of the pelvis,"},{"Start":"00:06.630 ","End":"00:13.800","Text":"the pelvic girdle, which attaches to the lower limbs of the axial skeleton."},{"Start":"00:13.800 ","End":"00:17.490","Text":"Its primary role is to support the weight of the upper body."},{"Start":"00:17.490 ","End":"00:20.235","Text":"It\u0027s quite large, this area."},{"Start":"00:20.235 ","End":"00:22.560","Text":"It supports this upper body,"},{"Start":"00:22.560 ","End":"00:26.490","Text":"both when sitting and when we\u0027re"},{"Start":"00:26.490 ","End":"00:32.025","Text":"standing by transferring the weight to the lower limbs when we\u0027re standing."},{"Start":"00:32.025 ","End":"00:40.220","Text":"It has these deep sockets with robust ligaments that attaches the femur,"},{"Start":"00:40.220 ","End":"00:42.875","Text":"that\u0027s the upper bone of the leg,"},{"Start":"00:42.875 ","End":"00:45.245","Text":"very firmly to the body."},{"Start":"00:45.245 ","End":"00:50.940","Text":"The pelvic girdle is further strengthened by 2 large hip bones."},{"Start":"00:50.940 ","End":"00:54.755","Text":"People often will break these bones when they get older."},{"Start":"00:54.755 ","End":"01:00.035","Text":"These are the bones that get broken part of the pelvic girdle."},{"Start":"01:00.035 ","End":"01:04.280","Text":"This very important hip joint is the junction"},{"Start":"01:04.280 ","End":"01:09.360","Text":"where the hip joins the leg to the trunk of the body."},{"Start":"01:09.970 ","End":"01:14.300","Text":"Let\u0027s look at these bones more carefully."},{"Start":"01:14.300 ","End":"01:19.550","Text":"The hip bones, sometimes they\u0027re called the coxal bones,"},{"Start":"01:19.550 ","End":"01:25.460","Text":"in adults are formed by the fusion of 3 pairs of bones: the ilium,"},{"Start":"01:25.460 ","End":"01:30.064","Text":"the ischium, and the pubis."},{"Start":"01:30.064 ","End":"01:34.190","Text":"These are 3 different bones that are formed separately in the fetus,"},{"Start":"01:34.190 ","End":"01:36.395","Text":"but fused in the adult,"},{"Start":"01:36.395 ","End":"01:40.009","Text":"and they create this pelvis."},{"Start":"01:40.009 ","End":"01:44.345","Text":"Now the pelvis of men and women is a little bit different."},{"Start":"01:44.345 ","End":"01:47.195","Text":"The female pelvis is larger,"},{"Start":"01:47.195 ","End":"01:51.380","Text":"and it has a somewhat different geometry,"},{"Start":"01:51.380 ","End":"01:53.540","Text":"although in general, it\u0027s the same."},{"Start":"01:53.540 ","End":"01:57.590","Text":"Of course, it has to have a geometry which allows for"},{"Start":"01:57.590 ","End":"02:03.310","Text":"childbirth and also to support a growing fetus."},{"Start":"02:03.310 ","End":"02:06.615","Text":"It has to be stronger from that standpoint."},{"Start":"02:06.615 ","End":"02:10.144","Text":"That\u0027s what we see here."},{"Start":"02:10.144 ","End":"02:11.735","Text":"Whereas in the male,"},{"Start":"02:11.735 ","End":"02:15.530","Text":"it has to be thicker and heavier and that has to"},{"Start":"02:15.530 ","End":"02:20.970","Text":"support the heavier build that typically men have."},{"Start":"02:21.110 ","End":"02:28.274","Text":"Let\u0027s look at the lower limbs now that extend below the pelvis."},{"Start":"02:28.274 ","End":"02:31.250","Text":"We have a thigh, of course,"},{"Start":"02:31.250 ","End":"02:33.935","Text":"and we have a leg,"},{"Start":"02:33.935 ","End":"02:36.495","Text":"and we have a foot."},{"Start":"02:36.495 ","End":"02:40.310","Text":"In the thigh, we\u0027ve got only 1 bone."},{"Start":"02:40.310 ","End":"02:42.920","Text":"It\u0027s very large, long."},{"Start":"02:42.920 ","End":"02:44.495","Text":"It\u0027s the largest bone in the body."},{"Start":"02:44.495 ","End":"02:46.070","Text":"It\u0027s the femur."},{"Start":"02:46.070 ","End":"02:48.050","Text":"The end of it is the patella,"},{"Start":"02:48.050 ","End":"02:50.270","Text":"that\u0027s the kneecap, covering the knee."},{"Start":"02:50.270 ","End":"02:53.840","Text":"Then looking further down in the leg,"},{"Start":"02:53.840 ","End":"02:57.755","Text":"we have the tibia and the fibula."},{"Start":"02:57.755 ","End":"03:02.223","Text":"Tibia is less strong than the femur,"},{"Start":"03:02.223 ","End":"03:05.300","Text":"but it\u0027s really our shin bone."},{"Start":"03:05.300 ","End":"03:07.949","Text":"Then we have the tarsals in the leg,"},{"Start":"03:07.949 ","End":"03:10.115","Text":"this is similar to what we had in the hand,"},{"Start":"03:10.115 ","End":"03:12.650","Text":"and we\u0027ve got metatarsals and phalanges,"},{"Start":"03:12.650 ","End":"03:16.175","Text":"similar to what we saw before in the hand."},{"Start":"03:16.175 ","End":"03:21.770","Text":"The lower limb bones are thicker and stronger than the upper limb bones."},{"Start":"03:21.770 ","End":"03:24.620","Text":"This is because the legs here have to support"},{"Start":"03:24.620 ","End":"03:28.640","Text":"the entire body and not just move other things around."},{"Start":"03:28.640 ","End":"03:31.190","Text":"Now let\u0027s look at these bones in more detail."},{"Start":"03:31.190 ","End":"03:34.700","Text":"Looking first at the femur, this thigh bone,"},{"Start":"03:34.700 ","End":"03:36.611","Text":"the top bone,"},{"Start":"03:36.611 ","End":"03:40.340","Text":"it\u0027s the only bone in the upper leg."},{"Start":"03:40.340 ","End":"03:42.110","Text":"We said there\u0027s only 1. It\u0027s the longest,"},{"Start":"03:42.110 ","End":"03:43.940","Text":"heaviest, strongest bone in the body,"},{"Start":"03:43.940 ","End":"03:50.045","Text":"and it articulates with the pelvis over here to form the proximal end of the hip joint."},{"Start":"03:50.045 ","End":"03:53.075","Text":"Then at the other end is the knee joint."},{"Start":"03:53.075 ","End":"03:56.045","Text":"Then it has the patella that covers it."},{"Start":"03:56.045 ","End":"03:58.062","Text":"Here\u0027s that patella, the kneecap."},{"Start":"03:58.062 ","End":"04:00.685","Text":"It\u0027s a triangular bone."},{"Start":"04:00.685 ","End":"04:06.920","Text":"Inside there is also embedded a tendon of the femoral extensors,"},{"Start":"04:06.920 ","End":"04:09.882","Text":"called the quadriceps,"},{"Start":"04:09.882 ","End":"04:13.019","Text":"are these tendons that are inside,"},{"Start":"04:13.019 ","End":"04:17.210","Text":"and it improves knee extension by reducing friction."},{"Start":"04:17.210 ","End":"04:21.350","Text":"The tibia, moving further down the large bone,"},{"Start":"04:21.350 ","End":"04:24.590","Text":"it\u0027s in the shin here,"},{"Start":"04:24.590 ","End":"04:26.930","Text":"is located directly below the knee,"},{"Start":"04:26.930 ","End":"04:28.745","Text":"and it\u0027s the second-largest bone."},{"Start":"04:28.745 ","End":"04:35.840","Text":"It articulates with the femur on 1 end and with the tarsal bones at the other end,"},{"Start":"04:35.840 ","End":"04:38.840","Text":"at the proximal end and the distal end."},{"Start":"04:38.840 ","End":"04:44.170","Text":"It\u0027s responsible for transmitting all that weight of the body to the foot."},{"Start":"04:44.170 ","End":"04:47.317","Text":"The fibula, which is the smaller bone,"},{"Start":"04:47.317 ","End":"04:49.820","Text":"it\u0027s on the back of the tibia,"},{"Start":"04:49.820 ","End":"04:51.170","Text":"parallels with it,"},{"Start":"04:51.170 ","End":"04:53.015","Text":"and articulates with the tibia,"},{"Start":"04:53.015 ","End":"04:54.815","Text":"but it\u0027s considerably smaller."},{"Start":"04:54.815 ","End":"04:56.795","Text":"It doesn\u0027t really bear weight,"},{"Start":"04:56.795 ","End":"04:59.720","Text":"but it acts as a site for muscle attachment and"},{"Start":"04:59.720 ","End":"05:03.530","Text":"forms the lateral part of the ankle joint,"},{"Start":"05:03.530 ","End":"05:10.280","Text":"so it helps move the foot relative to the leg."},{"Start":"05:10.280 ","End":"05:18.365","Text":"However, fast-running animals have a reduced ulna in the front leg and the fibula."},{"Start":"05:18.365 ","End":"05:21.985","Text":"They don\u0027t articulate it nearly as much."},{"Start":"05:21.985 ","End":"05:24.670","Text":"At the bottom, we\u0027ve got the foot,"},{"Start":"05:24.670 ","End":"05:27.450","Text":"which have the tarsal bones."},{"Start":"05:27.450 ","End":"05:29.800","Text":"It includes the calcaneus,"},{"Start":"05:29.800 ","End":"05:34.005","Text":"that\u0027s the heel bone really that projects posteriorly as the heel,"},{"Start":"05:34.005 ","End":"05:37.030","Text":"and the ankle then transmits the weight of the body"},{"Start":"05:37.030 ","End":"05:40.255","Text":"from the tibia and fibula to the foot."},{"Start":"05:40.255 ","End":"05:42.295","Text":"We\u0027ve got the metatarsals,"},{"Start":"05:42.295 ","End":"05:45.115","Text":"which are very similar to what we have in the hands,"},{"Start":"05:45.115 ","End":"05:51.625","Text":"5 of them, and then we have the phalanges that are at the very end."},{"Start":"05:51.625 ","End":"05:56.365","Text":"The tarsals and metatarsals form this longitudinal arch in the foot."},{"Start":"05:56.365 ","End":"05:57.854","Text":"That\u0027s the arch that\u0027s in our foot."},{"Start":"05:57.854 ","End":"06:00.250","Text":"You can see it displayed over here."},{"Start":"06:00.250 ","End":"06:03.310","Text":"It\u0027s an adaptation for carrying the weight,"},{"Start":"06:03.310 ","End":"06:05.930","Text":"adjust on our rear legs."},{"Start":"06:05.930 ","End":"06:07.610","Text":"Then we\u0027ve got the phalanges,"},{"Start":"06:07.610 ","End":"06:12.100","Text":"of which there are 14 bones in those toes."},{"Start":"06:12.100 ","End":"06:14.210","Text":"Each toe consists of 3 phalanges,"},{"Start":"06:14.210 ","End":"06:16.190","Text":"except for the big toe,"},{"Start":"06:16.190 ","End":"06:17.630","Text":"which has only 2,"},{"Start":"06:17.630 ","End":"06:20.960","Text":"and that\u0027s reminiscent of our thumb in our hands."},{"Start":"06:20.960 ","End":"06:25.775","Text":"The toes are very important for providing posture and balance,"},{"Start":"06:25.775 ","End":"06:31.710","Text":"and they support some of the body weight as well while we\u0027re walking."}],"ID":30252}],"Thumbnail":null,"ID":286919},{"Name":"Bone","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Bone Classification","Duration":"5m 30s","ChapterTopicVideoID":28723,"CourseChapterTopicPlaylistID":286920,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.130","Text":"In the previous video,"},{"Start":"00:02.130 ","End":"00:05.690","Text":"we gave you an introduction to bones in general,"},{"Start":"00:05.690 ","End":"00:09.333","Text":"and we discussed which bones are connected to which other bones,"},{"Start":"00:09.333 ","End":"00:12.435","Text":"a general survey of the bones in the body."},{"Start":"00:12.435 ","End":"00:16.260","Text":"In this video, we\u0027re going to discuss more closely what"},{"Start":"00:16.260 ","End":"00:20.160","Text":"bones are made of and how they change,"},{"Start":"00:20.160 ","End":"00:23.280","Text":"how they grow, how they get reabsorbed,"},{"Start":"00:23.280 ","End":"00:26.279","Text":"how they model themselves,"},{"Start":"00:26.279 ","End":"00:28.570","Text":"how they repair themselves after injury."},{"Start":"00:28.570 ","End":"00:35.330","Text":"We know that bone is a connective tissue that constitutes what\u0027s called the endoskeleton."},{"Start":"00:35.330 ","End":"00:37.430","Text":"Remember we talked about an exoskeleton."},{"Start":"00:37.430 ","End":"00:40.100","Text":"Animals like us have endoskeletons,"},{"Start":"00:40.100 ","End":"00:49.444","Text":"our skeletons are inside the body and they are divided into several different groups."},{"Start":"00:49.444 ","End":"00:52.520","Text":"They\u0027re classified by their shape,"},{"Start":"00:52.520 ","End":"00:55.220","Text":"basically, there are long bones,"},{"Start":"00:55.220 ","End":"00:57.019","Text":"there are short bones."},{"Start":"00:57.019 ","End":"01:02.675","Text":"There are flat bones like the sternum that\u0027s in the front of our chest."},{"Start":"01:02.675 ","End":"01:07.895","Text":"There are sesamoid bones like in the shape of a sesame seed,"},{"Start":"01:07.895 ","End":"01:10.670","Text":"like the patella, for instance, on our kneecap."},{"Start":"01:10.670 ","End":"01:15.860","Text":"There are irregular bones that have all sorts of strange shapes like the vertebra,"},{"Start":"01:15.860 ","End":"01:19.040","Text":"for instance, there are sutural bones."},{"Start":"01:19.040 ","End":"01:23.810","Text":"A suture is something that is like a tie,"},{"Start":"01:23.810 ","End":"01:26.300","Text":"we can say during surgery we suture,"},{"Start":"01:26.300 ","End":"01:29.000","Text":"it means we we stitch things up."},{"Start":"01:29.000 ","End":"01:30.920","Text":"There are bones in the skull,"},{"Start":"01:30.920 ","End":"01:33.935","Text":"for instance, which are sutural bones."},{"Start":"01:33.935 ","End":"01:39.020","Text":"Now let\u0027s look at each of these bones in greater detail,"},{"Start":"01:39.020 ","End":"01:42.760","Text":"starting with the long bones."},{"Start":"01:42.760 ","End":"01:48.900","Text":"These are defined as bones that are longer than they are wide,"},{"Start":"01:50.020 ","End":"01:54.595","Text":"and these bones also have a shaft,"},{"Start":"01:54.595 ","End":"01:57.275","Text":"and they have 2 different ends."},{"Start":"01:57.275 ","End":"02:01.070","Text":"Now, these bones have a primary function which"},{"Start":"02:01.070 ","End":"02:04.925","Text":"is to support body weight and to facilitate movement."},{"Start":"02:04.925 ","End":"02:07.610","Text":"These will be in our legs and our arms and so on."},{"Start":"02:07.610 ","End":"02:13.039","Text":"Now, these long bones are divided into 3 different sections."},{"Start":"02:13.039 ","End":"02:18.050","Text":"There\u0027s the diaphysis, which is the main central part of the bone."},{"Start":"02:18.050 ","End":"02:21.260","Text":"There is the proximal epiphysis,"},{"Start":"02:21.260 ","End":"02:22.865","Text":"which is one end,"},{"Start":"02:22.865 ","End":"02:25.795","Text":"and there\u0027s the distal epiphysis."},{"Start":"02:25.795 ","End":"02:30.620","Text":"These 2 different parts of the bone are wider,"},{"Start":"02:30.620 ","End":"02:36.710","Text":"and we\u0027ll see that they contain more bone marrow in them than the rest of the bones."},{"Start":"02:36.710 ","End":"02:41.470","Text":"That bone marrow is what produces blood cells."},{"Start":"02:41.470 ","End":"02:45.470","Text":"The bone is a live tissue it"},{"Start":"02:45.470 ","End":"02:49.895","Text":"contains within it blood vessels you\u0027ll see a contains within it nerves."},{"Start":"02:49.895 ","End":"02:52.085","Text":"Of course, you know that when you break a bone it hurts"},{"Start":"02:52.085 ","End":"02:54.860","Text":"and they can grow and they can change shape."},{"Start":"02:54.860 ","End":"02:57.785","Text":"They are very much alive."},{"Start":"02:57.785 ","End":"03:01.580","Text":"As we mentioned, limb bones are long bones,"},{"Start":"03:01.580 ","End":"03:06.120","Text":"and there are some exceptions to these that we have say"},{"Start":"03:06.120 ","End":"03:11.120","Text":"the patella and the bones of the wrist and the ankle are limb bones as well,"},{"Start":"03:11.120 ","End":"03:13.385","Text":"but they are short."},{"Start":"03:13.385 ","End":"03:16.450","Text":"They\u0027re actually different in shapes."},{"Start":"03:16.450 ","End":"03:21.380","Text":"Let\u0027s look at some short bones and some of them might be called cuboidal bones."},{"Start":"03:21.380 ","End":"03:23.690","Text":"Bones that are the same width and length,"},{"Start":"03:23.690 ","End":"03:25.220","Text":"so they\u0027re in a cube shape,"},{"Start":"03:25.220 ","End":"03:29.420","Text":"like you\u0027ll have this cuboidal bone in the foot."},{"Start":"03:29.420 ","End":"03:36.935","Text":"You also have them in the wrist as well as the ankle that you can see down here."},{"Start":"03:36.935 ","End":"03:42.954","Text":"The flat bones are thin like the sternum that we mentioned before,"},{"Start":"03:42.954 ","End":"03:45.590","Text":"and they may have somewhat of a curve, of course."},{"Start":"03:45.590 ","End":"03:48.470","Text":"Their primary function is to serve as a point of attachment for"},{"Start":"03:48.470 ","End":"03:52.730","Text":"muscles and largely to protect internal organs,"},{"Start":"03:52.730 ","End":"03:55.925","Text":"like the sternum will protect the internal organs."},{"Start":"03:55.925 ","End":"04:00.200","Text":"But there are also muscles that are attached to these bones."},{"Start":"04:00.200 ","End":"04:03.012","Text":"We have the sternum and we have the ribs, the scapula,"},{"Start":"04:03.012 ","End":"04:06.140","Text":"the shoulder blades, and the roof of the skull,"},{"Start":"04:06.140 ","End":"04:09.170","Text":"each of them are flat bones."},{"Start":"04:09.170 ","End":"04:12.785","Text":"Next we have these irregular bones that we mentioned,"},{"Start":"04:12.785 ","End":"04:14.210","Text":"like the pelvic bone,"},{"Start":"04:14.210 ","End":"04:16.820","Text":"for instance, and they may have"},{"Start":"04:16.820 ","End":"04:20.585","Text":"various pieces that are flat or notch that ridge or so on."},{"Start":"04:20.585 ","End":"04:24.890","Text":"Examples are vertebra hip bones and some of the skull bones."},{"Start":"04:24.890 ","End":"04:27.530","Text":"Next we\u0027ll look at this sesamoid bones."},{"Start":"04:27.530 ","End":"04:29.750","Text":"These are a small flat bones like the patella,"},{"Start":"04:29.750 ","End":"04:32.810","Text":"for instance, that are similar in shape to assess any seed,"},{"Start":"04:32.810 ","End":"04:38.810","Text":"and that\u0027s why they\u0027ve got this name and they\u0027re often embedded within a tendon."},{"Start":"04:38.810 ","End":"04:39.920","Text":"Here, for instance,"},{"Start":"04:39.920 ","End":"04:43.465","Text":"you could see the patella in the kneecap or it is a kneecap,"},{"Start":"04:43.465 ","End":"04:47.195","Text":"and you have these tendons which go over it and through it,"},{"Start":"04:47.195 ","End":"04:49.385","Text":"they serve as a pulley,"},{"Start":"04:49.385 ","End":"04:52.850","Text":"that provides smooth surface for these tendons to slide"},{"Start":"04:52.850 ","End":"04:56.885","Text":"over so that the tendons can transmit the muscular forces,"},{"Start":"04:56.885 ","End":"04:59.705","Text":"even if they\u0027re not in a straight line."},{"Start":"04:59.705 ","End":"05:02.120","Text":"Next, we\u0027ll look at the sutural bones."},{"Start":"05:02.120 ","End":"05:04.595","Text":"Sometimes they\u0027re called Wormian bones."},{"Start":"05:04.595 ","End":"05:08.180","Text":"In the skull we have a sutural bone that\u0027s shown over here and they\u0027re small,"},{"Start":"05:08.180 ","End":"05:09.845","Text":"flat, irregularly shaped,"},{"Start":"05:09.845 ","End":"05:13.520","Text":"and they are often found between larger,"},{"Start":"05:13.520 ","End":"05:15.860","Text":"flat bones that are in the skull."},{"Start":"05:15.860 ","End":"05:17.360","Text":"They vary in number, shape,"},{"Start":"05:17.360 ","End":"05:20.285","Text":"and size depending on their position."},{"Start":"05:20.285 ","End":"05:22.430","Text":"In our next video,"},{"Start":"05:22.430 ","End":"05:29.580","Text":"we\u0027ll look at bone tissue and see what the tissue is made of."}],"ID":30253},{"Watched":false,"Name":"Bone Tissue","Duration":"4m 33s","ChapterTopicVideoID":28725,"CourseChapterTopicPlaylistID":286920,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.650","Text":"Now let\u0027s look at the bone tissue itself."},{"Start":"00:04.650 ","End":"00:07.260","Text":"As I mentioned in the previous video,"},{"Start":"00:07.260 ","End":"00:09.615","Text":"of course, these bones are alive."},{"Start":"00:09.615 ","End":"00:11.145","Text":"They\u0027re organs."},{"Start":"00:11.145 ","End":"00:13.470","Text":"They contain blood,"},{"Start":"00:13.470 ","End":"00:15.134","Text":"connective tissue, nerves."},{"Start":"00:15.134 ","End":"00:17.070","Text":"They\u0027re alive."},{"Start":"00:17.070 ","End":"00:20.655","Text":"Now there are 2 types of bone tissue."},{"Start":"00:20.655 ","End":"00:22.514","Text":"We\u0027ve got compact bone,"},{"Start":"00:22.514 ","End":"00:25.890","Text":"and we\u0027ve got spongy bone. Let\u0027s see."},{"Start":"00:25.890 ","End":"00:33.135","Text":"Compact bone would be like the bone that\u0027s in the center of the bone in the diaphysis,"},{"Start":"00:33.135 ","End":"00:36.390","Text":"and we\u0027ve got spongy bone which is more spongy,"},{"Start":"00:36.390 ","End":"00:39.375","Text":"which we\u0027ll find in the epiphysis,"},{"Start":"00:39.375 ","End":"00:42.015","Text":"both sides, actually."},{"Start":"00:42.015 ","End":"00:45.170","Text":"Let\u0027s look at compact bone structure,"},{"Start":"00:45.170 ","End":"00:48.730","Text":"or cortical bone, more in detail."},{"Start":"00:48.730 ","End":"00:52.610","Text":"It forms the hard external layer of all bones"},{"Start":"00:52.610 ","End":"00:56.450","Text":"and surrounds the medullary cavity or bone marrow."},{"Start":"00:56.450 ","End":"00:59.515","Text":"On the outside of the bone,"},{"Start":"00:59.515 ","End":"01:01.355","Text":"we\u0027ve got this compact bone,"},{"Start":"01:01.355 ","End":"01:04.310","Text":"that\u0027s the hard bone that we think about when we think about bone."},{"Start":"01:04.310 ","End":"01:06.649","Text":"But as you can see, it has a structure,"},{"Start":"01:06.649 ","End":"01:10.505","Text":"and it provides the protection and the strength to the bones,"},{"Start":"01:10.505 ","End":"01:12.830","Text":"the part that\u0027s on the inside."},{"Start":"01:12.830 ","End":"01:17.435","Text":"This is like a pie wedge or a cross-section of the bone."},{"Start":"01:17.435 ","End":"01:22.100","Text":"It\u0027s enclosed where it is covered by articular cartilage."},{"Start":"01:22.100 ","End":"01:24.634","Text":"There might be some cartilage on the outside,"},{"Start":"01:24.634 ","End":"01:30.130","Text":"and it\u0027s covered by this material that is called periosteum."},{"Start":"01:30.880 ","End":"01:35.840","Text":"It\u0027s a thick fibrous membrane that covers the entire surfaces of bone,"},{"Start":"01:35.840 ","End":"01:39.530","Text":"and it serves as an attachment for muscles and tendons."},{"Start":"01:39.530 ","End":"01:42.890","Text":"This compact bone tissue contains"},{"Start":"01:42.890 ","End":"01:51.620","Text":"these smaller structures that are called Haversian systems or osteons."},{"Start":"01:51.620 ","End":"01:54.995","Text":"They have a particular structure as well."},{"Start":"01:54.995 ","End":"01:59.610","Text":"They contain a mineral matrix."},{"Start":"02:00.590 ","End":"02:05.675","Text":"That\u0027s the kind of cells that are in them,"},{"Start":"02:05.675 ","End":"02:10.445","Text":"these osteocytes, that are connected by canaliculi."},{"Start":"02:10.445 ","End":"02:19.610","Text":"These are these little areas that protrude throughout or outside of this cell membrane,"},{"Start":"02:19.610 ","End":"02:23.305","Text":"and they\u0027re going to transport blood."},{"Start":"02:23.305 ","End":"02:29.490","Text":"This is a channel that goes through the axis of the bone,"},{"Start":"02:29.490 ","End":"02:36.245","Text":"and each osteon, each of these, consists of lamellae."},{"Start":"02:36.245 ","End":"02:42.310","Text":"There are these various layers of compact matrix that surrounds the central canal."},{"Start":"02:42.310 ","End":"02:45.380","Text":"Let\u0027s look at this under a microscope slide."},{"Start":"02:45.380 ","End":"02:49.490","Text":"Here\u0027s the Haversian canal that we talked about,"},{"Start":"02:49.490 ","End":"02:54.200","Text":"and they house the nerve fibers and some capillaries."},{"Start":"02:54.200 ","End":"02:55.850","Text":"Remember it\u0027s alive,"},{"Start":"02:55.850 ","End":"02:59.180","Text":"and it\u0027s aligned in the same direction along the lines of stress in"},{"Start":"02:59.180 ","End":"03:03.995","Text":"the compact bone tissue and help the bone resist bending or fracturing."},{"Start":"03:03.995 ","End":"03:09.865","Text":"The compact bone tissue is prominent in areas of bone at which stresses are applied."},{"Start":"03:09.865 ","End":"03:12.470","Text":"Of course that makes sense because"},{"Start":"03:12.470 ","End":"03:15.634","Text":"it helps the bone resist the bending and the fracturing."},{"Start":"03:15.634 ","End":"03:19.820","Text":"There are these canals or these osteons."},{"Start":"03:19.820 ","End":"03:25.130","Text":"These canals are applied in only a few different directions."},{"Start":"03:25.130 ","End":"03:28.340","Text":"Let\u0027s go on now to discuss the spongy bone."},{"Start":"03:28.340 ","End":"03:31.955","Text":"It\u0027s called also the cancellous tissue."},{"Start":"03:31.955 ","End":"03:38.315","Text":"Remember that\u0027s the spongy area that\u0027s at the ends of the long bones."},{"Start":"03:38.315 ","End":"03:41.780","Text":"They contain the spongy material."},{"Start":"03:41.780 ","End":"03:45.020","Text":"Now they\u0027re also compressible because"},{"Start":"03:45.020 ","End":"03:49.235","Text":"the stress is a little bit different in these areas."},{"Start":"03:49.235 ","End":"03:54.470","Text":"We have joints where 2 different bones will come together,"},{"Start":"03:54.470 ","End":"03:59.080","Text":"and the stresses are in various directions here."},{"Start":"03:59.080 ","End":"04:02.025","Text":"Therefore, they are compressible,"},{"Start":"04:02.025 ","End":"04:06.770","Text":"and of course they are located at the ends of the long bones at the epiphysis."},{"Start":"04:06.770 ","End":"04:10.840","Text":"The compact bone is more in the center."},{"Start":"04:10.840 ","End":"04:14.315","Text":"These don\u0027t contain these osteons,"},{"Start":"04:14.315 ","End":"04:15.560","Text":"which are much harder,"},{"Start":"04:15.560 ","End":"04:18.170","Text":"but instead they contain trabeculae,"},{"Start":"04:18.170 ","End":"04:20.375","Text":"plates and bars of bones."},{"Start":"04:20.375 ","End":"04:22.190","Text":"That\u0027s what\u0027s the structure,"},{"Start":"04:22.190 ","End":"04:24.890","Text":"as you can see is different in this area."},{"Start":"04:24.890 ","End":"04:30.305","Text":"Inside between them are these irregular cavities that contain the red bone marrow,"},{"Start":"04:30.305 ","End":"04:32.910","Text":"which is the organ that it forms."}],"ID":30254},{"Watched":false,"Name":"Bone Cells","Duration":"6m 4s","ChapterTopicVideoID":28724,"CourseChapterTopicPlaylistID":286920,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.530","Text":"I\u0027m glad you\u0027re back to discuss more about bones."},{"Start":"00:04.530 ","End":"00:08.835","Text":"We discussed before in the previous videos that general structure of bones."},{"Start":"00:08.835 ","End":"00:11.475","Text":"Now let\u0027s look at the cells that compose the bones."},{"Start":"00:11.475 ","End":"00:14.235","Text":"We see that there are different types of cells,"},{"Start":"00:14.235 ","End":"00:17.055","Text":"and the bone consists of 4 different types,"},{"Start":"00:17.055 ","End":"00:25.190","Text":"osteoblasts, osteocytes, osteoclasts, and osteogenic cells."},{"Start":"00:25.190 ","End":"00:31.130","Text":"Each of those lit up here as I was moving through the list."},{"Start":"00:31.130 ","End":"00:35.030","Text":"Osteoblasts, osteocytes and you can see they have"},{"Start":"00:35.030 ","End":"00:39.440","Text":"different shape osteoclasts and osteogenic cells."},{"Start":"00:39.440 ","End":"00:42.035","Text":"Now, what did each of these cell types do?"},{"Start":"00:42.035 ","End":"00:47.135","Text":"Each of them has a unique function and is also found in different locations in the bones."},{"Start":"00:47.135 ","End":"00:50.390","Text":"Let\u0027s start with the osteoblasts."},{"Start":"00:50.390 ","End":"00:55.100","Text":"Blasts remember, are going to be cells that are going to form other kinds of cells."},{"Start":"00:55.100 ","End":"00:58.910","Text":"We saw myoblasts before in a previous video."},{"Start":"00:58.910 ","End":"01:02.599","Text":"These are bone forming cells because they\u0027re osteo."},{"Start":"01:02.599 ","End":"01:10.265","Text":"Osteo means bone and they will be found at the edge of the tissue."},{"Start":"01:10.265 ","End":"01:14.870","Text":"They secrete collagen and an organic matrix of bone,"},{"Start":"01:14.870 ","End":"01:20.690","Text":"which becomes calcified and it absorbs calcium sooner after has been deposited."},{"Start":"01:20.690 ","End":"01:22.430","Text":"You can see that over here,"},{"Start":"01:22.430 ","End":"01:28.470","Text":"there are osteoblasts that are at the edge of this tissue they\u0027re being formed."},{"Start":"01:28.470 ","End":"01:31.760","Text":"Then they are trapped in the secretions that they make,"},{"Start":"01:31.760 ","End":"01:38.905","Text":"and they then differentiate into osteocytes."},{"Start":"01:38.905 ","End":"01:45.080","Text":"These osteocytes then are the main cells in the mature bony connective tissue."},{"Start":"01:45.080 ","End":"01:50.345","Text":"Here\u0027s an osteocyte within a lacuna that we discussed before."},{"Start":"01:50.345 ","End":"01:55.445","Text":"The osteocytes cannot divide once they\u0027ve been made."},{"Start":"01:55.445 ","End":"01:57.925","Text":"That\u0027s common to cells that have differentiated."},{"Start":"01:57.925 ","End":"02:00.890","Text":"They maintain a normal bone structure by sending signals of"},{"Start":"02:00.890 ","End":"02:05.600","Text":"bone formation or bone re-absorption or resorption into the bone surface."},{"Start":"02:05.600 ","End":"02:07.040","Text":"As we mentioned before,"},{"Start":"02:07.040 ","End":"02:11.930","Text":"bones are both made and destroyed sometimes as resorption"},{"Start":"02:11.930 ","End":"02:17.735","Text":"of the tissue say if we need more calcium and we\u0027ll come back to that before."},{"Start":"02:17.735 ","End":"02:24.995","Text":"There is these osteocytes occupy a small chamber called the lacuna that we mentioned,"},{"Start":"02:24.995 ","End":"02:28.880","Text":"and it is inside the calcified matrix of bone."},{"Start":"02:28.880 ","End":"02:32.510","Text":"Each of these lacuna is connected to other lacuna through"},{"Start":"02:32.510 ","End":"02:38.180","Text":"these fine network of these canonicals that we also mentioned a little bit earlier."},{"Start":"02:38.180 ","End":"02:42.050","Text":"So these canaliculi supply nutrients to"},{"Start":"02:42.050 ","End":"02:44.330","Text":"the osteocytes and they also remove"},{"Start":"02:44.330 ","End":"02:46.730","Text":"cellular waste and enable communication between the cells."},{"Start":"02:46.730 ","End":"02:49.460","Text":"These little like little canals between the cells."},{"Start":"02:49.460 ","End":"02:53.630","Text":"Next cell type are osteoclasts."},{"Start":"02:53.630 ","End":"02:59.540","Text":"Osteoclasts, they\u0027re large and they are multi-nucleated cells."},{"Start":"02:59.540 ","End":"03:03.290","Text":"Multi-nucleated remember sometimes are actually"},{"Start":"03:03.290 ","End":"03:07.565","Text":"muscle fibers are also multi-nucleated and they are,"},{"Start":"03:07.565 ","End":"03:12.740","Text":"the osteoclasts are responsible for the dissolution and absorption of bone,"},{"Start":"03:12.740 ","End":"03:14.330","Text":"as we mentioned a moment ago,"},{"Start":"03:14.330 ","End":"03:18.530","Text":"they can remove bone structure by releasing lysosomal enzymes."},{"Start":"03:18.530 ","End":"03:22.940","Text":"These lysosomal enzymes are going to digest proteins."},{"Start":"03:22.940 ","End":"03:29.095","Text":"They can also release acids that may dissolve the calcification."},{"Start":"03:29.095 ","End":"03:33.590","Text":"They help regulate calcium concentration and body fluids in this way."},{"Start":"03:33.590 ","End":"03:38.015","Text":"Therefore, when they are remodeled or resorbed,"},{"Start":"03:38.015 ","End":"03:41.690","Text":"then the calcium levels in the blood may go"},{"Start":"03:41.690 ","End":"03:46.880","Text":"up and they are sensitive to stresses that the body may see."},{"Start":"03:46.880 ","End":"03:52.669","Text":"The last kind of bone that we want to talk about are the osteogenic cells."},{"Start":"03:52.669 ","End":"03:54.650","Text":"These are progenitor cells."},{"Start":"03:54.650 ","End":"03:58.260","Text":"These are cells which are going to become something else."},{"Start":"03:58.260 ","End":"04:02.255","Text":"You see we haven\u0027t osteogenic cell develops into an osteoblast,"},{"Start":"04:02.255 ","End":"04:07.360","Text":"which is then going to form the osteocytes,"},{"Start":"04:07.360 ","End":"04:10.490","Text":"maintain the bone tissue as we saw before."},{"Start":"04:10.490 ","End":"04:13.700","Text":"These are squamous stem cells are stem cells that divide to"},{"Start":"04:13.700 ","End":"04:17.105","Text":"produce daughter cells that can differentiated."},{"Start":"04:17.105 ","End":"04:24.890","Text":"They play a very important role in bone repair and growth."},{"Start":"04:24.890 ","End":"04:27.371","Text":"Under appropriate circumstances,"},{"Start":"04:27.371 ","End":"04:31.550","Text":"then they also have the potential to differentiate into other kinds of tissue."},{"Start":"04:31.550 ","End":"04:33.740","Text":"They could differentiate the fibroblasts,"},{"Start":"04:33.740 ","End":"04:36.245","Text":"adipocytes, chondrocytes, muscle cells,"},{"Start":"04:36.245 ","End":"04:43.100","Text":"even these osteogenic cells are sitting around and they\u0027re waiting to develop"},{"Start":"04:43.100 ","End":"04:46.700","Text":"into whatever kind of tissue that needs to develop into depending on what\u0027s"},{"Start":"04:46.700 ","End":"04:50.870","Text":"going on around them and what signals they get."},{"Start":"04:50.870 ","End":"04:55.730","Text":"Let\u0027s go on now to discuss the development of bone,"},{"Start":"04:55.730 ","End":"04:58.670","Text":"the ossification of the bone."},{"Start":"04:58.670 ","End":"05:03.350","Text":"That\u0027s where the bone becomes hard process of bone formation by"},{"Start":"05:03.350 ","End":"05:08.480","Text":"the osteoblasts and it begins about 6 weeks after fertilization of the embryo,"},{"Start":"05:08.480 ","End":"05:10.730","Text":"of course, there are no bones at the very beginning."},{"Start":"05:10.730 ","End":"05:15.454","Text":"With time, what happens is that cartilage forms."},{"Start":"05:15.454 ","End":"05:17.890","Text":"There are blood vessels that form there is"},{"Start":"05:17.890 ","End":"05:21.905","Text":"a cavity which is formed that gets blood vessels inside it."},{"Start":"05:21.905 ","End":"05:24.530","Text":"We have the development of compact bone and"},{"Start":"05:24.530 ","End":"05:28.385","Text":"the secondary ossification centers and the growth of the bone."},{"Start":"05:28.385 ","End":"05:30.110","Text":"Before any of this,"},{"Start":"05:30.110 ","End":"05:37.375","Text":"the embryonic skeleton consists of this fibrous membranes and a kind of cartilage."},{"Start":"05:37.375 ","End":"05:44.615","Text":"But bone growth is not only during childhood or during embryo-genesis."},{"Start":"05:44.615 ","End":"05:47.885","Text":"It grows throughout childhood of course."},{"Start":"05:47.885 ","End":"05:49.460","Text":"Even in adults,"},{"Start":"05:49.460 ","End":"05:51.065","Text":"it can change its shape."},{"Start":"05:51.065 ","End":"05:53.795","Text":"Bones can grow in thickness throughout life as we said."},{"Start":"05:53.795 ","End":"05:57.275","Text":"But in humans after the age of 25, ossification,"},{"Start":"05:57.275 ","End":"06:04.380","Text":"that is this hardening functions primarily in bone remodeling and repair, not in growth."}],"ID":30255},{"Watched":false,"Name":"Bone Growth","Duration":"6m 26s","ChapterTopicVideoID":28722,"CourseChapterTopicPlaylistID":286920,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.860","Text":"Hi. Welcome back to our discussion of bones."},{"Start":"00:06.410 ","End":"00:10.830","Text":"In this video, we\u0027re going to talk about development, really, of bone,"},{"Start":"00:10.830 ","End":"00:16.515","Text":"about how bones grow and about how they remodel."},{"Start":"00:16.515 ","End":"00:23.010","Text":"Let\u0027s start our discussion by talking about intramembranous ossification."},{"Start":"00:23.010 ","End":"00:28.581","Text":"\"Intramembrane\" means within the membrane,"},{"Start":"00:28.581 ","End":"00:30.225","Text":"so the \"ossification\","},{"Start":"00:30.225 ","End":"00:32.705","Text":"the hardening of the membrane."},{"Start":"00:32.705 ","End":"00:38.535","Text":"This is the process of bone development from fibrous membranes."},{"Start":"00:38.535 ","End":"00:41.255","Text":"It\u0027s involved in the formation, primarily,"},{"Start":"00:41.255 ","End":"00:43.040","Text":"of the flat bones, for instance,"},{"Start":"00:43.040 ","End":"00:45.650","Text":"skull, mandible, and the clavicles."},{"Start":"00:45.650 ","End":"00:47.300","Text":"There are several steps to this."},{"Start":"00:47.300 ","End":"00:49.340","Text":"Let\u0027s first look at the first step."},{"Start":"00:49.340 ","End":"00:56.475","Text":"This ossification begins as mesenchymal cells here that form a template."},{"Start":"00:56.475 ","End":"01:00.470","Text":"In other words, they grow in such a way that they will"},{"Start":"01:00.470 ","End":"01:04.890","Text":"form a structure upon which the bone will form,"},{"Start":"01:04.890 ","End":"01:07.325","Text":"so it\u0027s a template of the future bone."},{"Start":"01:07.325 ","End":"01:14.420","Text":"Then they differentiate from these mesenchymal cells into osteoblasts."},{"Start":"01:16.510 ","End":"01:27.595","Text":"Those osteoblasts then are going to secrete an extracellular matrix and deposit calcium."},{"Start":"01:27.595 ","End":"01:32.590","Text":"This mixture is called an osteoid, which hardens."},{"Start":"01:32.590 ","End":"01:37.325","Text":"This hardening occurs then within the bone,"},{"Start":"01:37.325 ","End":"01:41.570","Text":"and they become osteocytes."},{"Start":"01:41.570 ","End":"01:44.995","Text":"The osteoblasts then become osteocytes."},{"Start":"01:44.995 ","End":"01:48.409","Text":"You can see the osteoblasts around the outside."},{"Start":"01:48.409 ","End":"01:50.300","Text":"At the ossification centers,"},{"Start":"01:50.300 ","End":"01:54.040","Text":"we get these osteocytes that form."},{"Start":"01:54.040 ","End":"01:56.400","Text":"Looking in more detail,"},{"Start":"01:56.400 ","End":"02:04.085","Text":"we see the third step now is trabecular matrix and periosteum form."},{"Start":"02:04.085 ","End":"02:07.114","Text":"We said that these 2 matrices form."},{"Start":"02:07.114 ","End":"02:15.080","Text":"We have the mesenchymal cells on the outside that form in the periosteum."},{"Start":"02:15.080 ","End":"02:20.600","Text":"This is outside of where the spongy material is going to be in the bone."},{"Start":"02:20.600 ","End":"02:25.565","Text":"Inside, we have these trabeculae which are formed."},{"Start":"02:25.565 ","End":"02:28.100","Text":"Of course, there are blood vessels in there as well."},{"Start":"02:28.100 ","End":"02:35.285","Text":"The spongy material then is remodeled into these thin layers of compact bone."},{"Start":"02:35.285 ","End":"02:41.945","Text":"Here you can see the compact bone which is formed on the surface of the spongy bone."},{"Start":"02:41.945 ","End":"02:45.980","Text":"This was intramembranous ossification."},{"Start":"02:45.980 ","End":"02:50.525","Text":"Now let\u0027s look at endochondral ossification."},{"Start":"02:50.525 ","End":"02:54.515","Text":"These are all the other bones of the body,"},{"Start":"02:54.515 ","End":"02:57.535","Text":"except for the flat bones that we discussed before."},{"Start":"02:57.535 ","End":"03:01.415","Text":"Here we have a different model for the formation of bone."},{"Start":"03:01.415 ","End":"03:08.525","Text":"We start out with a hyaline cartilage model that you can see depicted over here."},{"Start":"03:08.525 ","End":"03:15.815","Text":"The bone becomes a little bit bigger by creating a cartilage around the outside."},{"Start":"03:15.815 ","End":"03:18.575","Text":"The cartilage begins to calcify later,"},{"Start":"03:18.575 ","End":"03:22.040","Text":"and then a bone collar forms."},{"Start":"03:22.040 ","End":"03:26.310","Text":"That\u0027s this line that we can see over here."},{"Start":"03:28.490 ","End":"03:33.125","Text":"There\u0027s an ossification center which occurs within the bone."},{"Start":"03:33.125 ","End":"03:35.360","Text":"It\u0027s in the diaphysis,"},{"Start":"03:35.360 ","End":"03:36.500","Text":"this longer part of the growth part."},{"Start":"03:36.500 ","End":"03:38.780","Text":"At the growth plate,"},{"Start":"03:38.780 ","End":"03:45.740","Text":"there\u0027s a particular area that grows until the epiphyseal plates ossify later."},{"Start":"03:45.740 ","End":"03:48.980","Text":"Let\u0027s look at this in a bit more detail."},{"Start":"03:48.980 ","End":"03:52.220","Text":"In our next step, the ossification centers form,"},{"Start":"03:52.220 ","End":"03:53.884","Text":"very much as we saw earlier,"},{"Start":"03:53.884 ","End":"03:55.835","Text":"in the epiphysis,"},{"Start":"03:55.835 ","End":"03:59.450","Text":"and bone replaces almost all of this cartilage."},{"Start":"03:59.450 ","End":"04:02.960","Text":"You can see that there is a medullary cavity,"},{"Start":"04:02.960 ","End":"04:05.419","Text":"a cavity which is inside the cell,"},{"Start":"04:05.419 ","End":"04:06.770","Text":"and around it,"},{"Start":"04:06.770 ","End":"04:11.570","Text":"we have the secondary ossification center forming."},{"Start":"04:11.570 ","End":"04:15.965","Text":"There\u0027s the arteries and veins which go in and out of the bone."},{"Start":"04:15.965 ","End":"04:18.424","Text":"The bone replaces all this cartilage,"},{"Start":"04:18.424 ","End":"04:21.979","Text":"and there\u0027s therefore lengthwise growth,"},{"Start":"04:21.979 ","End":"04:29.210","Text":"which continues at a particular plate at this epiphyseal plate,"},{"Start":"04:29.210 ","End":"04:35.480","Text":"the growth plate, until the plates later ossify at puberty."},{"Start":"04:35.480 ","End":"04:41.055","Text":"The bones then lengthen by interstitial growth,"},{"Start":"04:41.055 ","End":"04:44.840","Text":"the longitudinal growth of the bone, in other words,"},{"Start":"04:44.840 ","End":"04:48.285","Text":"getting longer, increases the bone length,"},{"Start":"04:48.285 ","End":"04:52.130","Text":"and then we have the formation of this bone plate,"},{"Start":"04:52.130 ","End":"04:54.095","Text":"the cartilage growth plate,"},{"Start":"04:54.095 ","End":"04:56.825","Text":"where most of the growth occurs,"},{"Start":"04:56.825 ","End":"05:00.440","Text":"and it seals with puberty, as we said."},{"Start":"05:00.440 ","End":"05:02.870","Text":"So the lengthening stages are chondrocytes on"},{"Start":"05:02.870 ","End":"05:05.878","Text":"the epiphyseal side of the epiphyseal plate divide,"},{"Start":"05:05.878 ","End":"05:08.570","Text":"the particular cells, they divide,"},{"Start":"05:08.570 ","End":"05:15.565","Text":"and 1 of the cells remains undifferentiated near the epiphysis,"},{"Start":"05:15.565 ","End":"05:19.649","Text":"and 1 cell moves towards the diaphysis."},{"Start":"05:19.649 ","End":"05:21.580","Text":"So the cells are moving down."},{"Start":"05:21.580 ","End":"05:26.985","Text":"We have addition of bones over here added to the diaphysis."},{"Start":"05:26.985 ","End":"05:29.950","Text":"On the diaphyseal side,"},{"Start":"05:29.950 ","End":"05:32.335","Text":"the cartilage is replaced with bone,"},{"Start":"05:32.335 ","End":"05:35.410","Text":"resulting in the lengthening of the bone."},{"Start":"05:35.410 ","End":"05:42.460","Text":"I mentioned earlier that puberty is when these plates are closed."},{"Start":"05:42.460 ","End":"05:45.759","Text":"We have ossification of those plates."},{"Start":"05:45.759 ","End":"05:54.145","Text":"This is mediated by estrogen in females and testosterone in males."},{"Start":"05:54.145 ","End":"05:56.319","Text":"When the bone growth is complete,"},{"Start":"05:56.319 ","End":"05:58.450","Text":"the cartilage is replaced with bone,"},{"Start":"05:58.450 ","End":"06:01.930","Text":"and it joins to the diaphysis."},{"Start":"06:01.930 ","End":"06:08.525","Text":"This occurs around the age of 18 in females and around the age of 21 in males."},{"Start":"06:08.525 ","End":"06:17.239","Text":"The boundary between the epiphyses and the diaphysis at this time is marked with a line."},{"Start":"06:17.239 ","End":"06:21.190","Text":"That\u0027s where the plate was earlier."},{"Start":"06:21.190 ","End":"06:25.930","Text":"Here\u0027s the plate and now it\u0027s becomes a line."}],"ID":30256},{"Watched":false,"Name":"Bone Remodelling and Repair","Duration":"4m 39s","ChapterTopicVideoID":28726,"CourseChapterTopicPlaylistID":286920,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:01.935","Text":"In the last video,"},{"Start":"00:01.935 ","End":"00:05.601","Text":"we spoke of bone growth in a longitudinal sense,"},{"Start":"00:05.601 ","End":"00:07.649","Text":"in other words, getting longer."},{"Start":"00:07.649 ","End":"00:13.360","Text":"Now we\u0027re going to talk about appositional growth."},{"Start":"00:13.490 ","End":"00:16.950","Text":"That means increasing the diameter of the bones by"},{"Start":"00:16.950 ","End":"00:19.710","Text":"the addition of bony tissue at the surface of the bones,"},{"Start":"00:19.710 ","End":"00:21.930","Text":"in other words, getting thicker."},{"Start":"00:21.930 ","End":"00:24.015","Text":"As you can see here,"},{"Start":"00:24.015 ","End":"00:27.030","Text":"we have a bone in an infant,"},{"Start":"00:27.030 ","End":"00:28.969","Text":"which is very narrow, of course,"},{"Start":"00:28.969 ","End":"00:32.790","Text":"and as the child gets older and becomes an adult,"},{"Start":"00:32.790 ","End":"00:35.120","Text":"it gets wider,"},{"Start":"00:35.120 ","End":"00:38.440","Text":"but the outside hard,"},{"Start":"00:38.440 ","End":"00:41.690","Text":"calcified part of the bone is going to"},{"Start":"00:41.690 ","End":"00:47.255","Text":"disappear and be replaced by material on the outside."},{"Start":"00:47.255 ","End":"00:50.300","Text":"How does that happen? There are"},{"Start":"00:50.300 ","End":"00:54.680","Text":"osteoblasts at the bone surface that secrete the bone matrix,"},{"Start":"00:54.680 ","End":"00:56.315","Text":"as we\u0027ve mentioned before."},{"Start":"00:56.315 ","End":"00:59.900","Text":"But in addition to that, there are osteoclasts on"},{"Start":"00:59.900 ","End":"01:03.720","Text":"the inner surface that break down the bone."},{"Start":"01:03.720 ","End":"01:07.500","Text":"So we have bone resorbed by osteoclasts."},{"Start":"01:07.500 ","End":"01:12.565","Text":"At the same time, we have new bone deposited by the osteoblasts."},{"Start":"01:12.565 ","End":"01:18.080","Text":"This balance between these 2 processes allows the bone to thicken,"},{"Start":"01:18.080 ","End":"01:19.655","Text":"to become wider,"},{"Start":"01:19.655 ","End":"01:23.705","Text":"but it does not necessarily become that heavy"},{"Start":"01:23.705 ","End":"01:28.940","Text":"because the interior of the bone is less dense than the outside."},{"Start":"01:28.940 ","End":"01:33.560","Text":"This really is a kind of bone remodeling."},{"Start":"01:33.560 ","End":"01:39.170","Text":"It\u0027s the replacement of the old bone tissue by new bone tissue. What do we see?"},{"Start":"01:39.170 ","End":"01:43.985","Text":"We see that it involves the process of bone deposition by"},{"Start":"01:43.985 ","End":"01:50.230","Text":"osteoblasts but bone resorption by osteoclasts."},{"Start":"01:50.230 ","End":"01:58.640","Text":"What we see here is that the osteoblasts that are here replace the osteoclasts."},{"Start":"01:58.640 ","End":"02:02.735","Text":"The osteoclasts are going to dissolve"},{"Start":"02:02.735 ","End":"02:08.105","Text":"the osteocytes and the bone tissue that\u0027s next to it."},{"Start":"02:08.105 ","End":"02:13.820","Text":"Then the osteoblasts develop and differentiate,"},{"Start":"02:13.820 ","End":"02:15.860","Text":"creating new bone,"},{"Start":"02:15.860 ","End":"02:17.555","Text":"and at the same time,"},{"Start":"02:17.555 ","End":"02:23.387","Text":"there is a line which is created between the new bone and the old bone."},{"Start":"02:23.387 ","End":"02:29.180","Text":"There are different states: there\u0027s the resting state of the osteoblasts to begin with,"},{"Start":"02:29.180 ","End":"02:31.700","Text":"there\u0027s the resorption by the osteoclasts,"},{"Start":"02:31.700 ","End":"02:33.125","Text":"there\u0027s this reversal,"},{"Start":"02:33.125 ","End":"02:38.720","Text":"in other words, there\u0027s again the growth of the osteoblasts,"},{"Start":"02:38.720 ","End":"02:41.420","Text":"the formation of new material, mineralization,"},{"Start":"02:41.420 ","End":"02:47.000","Text":"as we saw earlier, and then we\u0027re back to a resting state."},{"Start":"02:47.000 ","End":"02:51.080","Text":"This normal bone growth requires vitamins, D, C,"},{"Start":"02:51.080 ","End":"02:53.060","Text":"and A, and of course, minerals,"},{"Start":"02:53.060 ","End":"02:55.835","Text":"calcium, phosphorus, and magnesium."},{"Start":"02:55.835 ","End":"03:02.930","Text":"This entire system is affected by parathyroid hormone,"},{"Start":"03:02.930 ","End":"03:04.940","Text":"growth hormone, calcitonin,"},{"Start":"03:04.940 ","End":"03:06.470","Text":"of course, we saw earlier."},{"Start":"03:06.470 ","End":"03:10.820","Text":"All these are required for proper bone growth and maintenance."},{"Start":"03:10.820 ","End":"03:14.540","Text":"This allows bones to remodel and to adapt to"},{"Start":"03:14.540 ","End":"03:19.690","Text":"stresses by becoming thicker and stronger when subjected to stress."},{"Start":"03:19.690 ","End":"03:23.945","Text":"Amazingly, the turnover rate here is quite high."},{"Start":"03:23.945 ","End":"03:30.515","Text":"About 5-7 percent of bone mass is actually recycled every week."},{"Start":"03:30.515 ","End":"03:33.590","Text":"Isn\u0027t that amazing? Now, lastly,"},{"Start":"03:33.590 ","End":"03:37.020","Text":"let\u0027s look at bone repair."},{"Start":"03:37.120 ","End":"03:41.315","Text":"If a bone is broken or fractured,"},{"Start":"03:41.315 ","End":"03:44.930","Text":"then it undergoes repair through 4 different stages."},{"Start":"03:44.930 ","End":"03:48.935","Text":"There is a formation of a hematoma because when the bone is broken,"},{"Start":"03:48.935 ","End":"03:55.565","Text":"blood vessels are broken and that provides the framework for the regrowth to occur."},{"Start":"03:55.565 ","End":"04:03.515","Text":"There is a callus formation around this area that occurs between days 5-11."},{"Start":"04:03.515 ","End":"04:08.695","Text":"It\u0027s new fibrous tissue with cartilage around this fracture."},{"Start":"04:08.695 ","End":"04:12.410","Text":"Then there is the formation of a more of"},{"Start":"04:12.410 ","End":"04:18.110","Text":"a bony callus as opposed to the callus that we had before, the spongy callus."},{"Start":"04:18.110 ","End":"04:19.550","Text":"Now it\u0027s more of a bony callus,"},{"Start":"04:19.550 ","End":"04:24.160","Text":"and hard bone begins to replace a soft spongy tissues."},{"Start":"04:24.160 ","End":"04:28.940","Text":"Eventually, there\u0027s the end of this bone remodeling on which"},{"Start":"04:28.940 ","End":"04:34.535","Text":"solid bone continues to grow and blood circulation improves at the fracture site,"},{"Start":"04:34.535 ","End":"04:39.180","Text":"leaving us with a repaired bone."}],"ID":30257}],"Thumbnail":null,"ID":286920},{"Name":"Joints and Skeletal Movement","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Joints Between the Bones","Duration":"8m 33s","ChapterTopicVideoID":28721,"CourseChapterTopicPlaylistID":286921,"HasSubtitles":true,"ThumbnailPath":"https://www.proprep.uk/Images/Videos_Thumbnails/28721.jpeg","UploadDate":"2022-03-24T07:40:50.7230000","DurationForVideoObject":"PT8M33S","Description":null,"MetaTitle":"Joints Between the Bones: Video + Workbook | Proprep","MetaDescription":"The Musculoskelletal System - Joints and Skeletal Movement. Watch the video made by an expert in the field. Download the workbook and maximize your learning.","Canonical":"https://www.proprep.uk/general-modules/all/introduction-to-biology/the-musculoskelletal-system/joints-and-skeletal-movement/vid30258","VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.190","Text":"We\u0027ve been speaking about bones in the previous videos,"},{"Start":"00:05.190 ","End":"00:09.630","Text":"and now we get to the point where we need to talk about how those bones"},{"Start":"00:09.630 ","End":"00:14.400","Text":"connect with one another and how they move with respect to one another."},{"Start":"00:14.400 ","End":"00:20.670","Text":"That\u0027s what we\u0027re talking about when we\u0027re talking about joint articulation."},{"Start":"00:20.670 ","End":"00:26.805","Text":"Articulation, that\u0027s the point at which 2 or more bones meet."},{"Start":"00:26.805 ","End":"00:34.380","Text":"What we\u0027re going to see is that typically these joints,"},{"Start":"00:34.380 ","End":"00:37.410","Text":"the places when which the bones meet,"},{"Start":"00:37.410 ","End":"00:42.195","Text":"are typically formed of a fibrous connective tissue and cartilage."},{"Start":"00:42.195 ","End":"00:45.850","Text":"Now those things are going to be responsible for the movement"},{"Start":"00:45.850 ","End":"00:49.850","Text":"of the bones one with respect to the other,"},{"Start":"00:49.850 ","End":"00:51.965","Text":"for instance, the movement of the limbs,"},{"Start":"00:51.965 ","End":"00:55.745","Text":"but these joints have to be stable."},{"Start":"00:55.745 ","End":"01:01.640","Text":"That is, they have to not move out of the place where they should be,"},{"Start":"01:01.640 ","End":"01:06.100","Text":"and sometimes that involves keeping them in place,"},{"Start":"01:06.100 ","End":"01:10.480","Text":"when they\u0027re moving one with respect to the other and so they just don\u0027t fall apart."},{"Start":"01:10.480 ","End":"01:13.250","Text":"In other cases, it\u0027s going to mean they\u0027re"},{"Start":"01:13.250 ","End":"01:16.520","Text":"going to really stay very close to one another."},{"Start":"01:16.520 ","End":"01:22.190","Text":"The skull is made up of these various different bones,"},{"Start":"01:22.190 ","End":"01:25.425","Text":"as we mentioned before and the interaction between or"},{"Start":"01:25.425 ","End":"01:29.089","Text":"the place between the 2 are actually joints."},{"Start":"01:29.089 ","End":"01:35.315","Text":"What we do is we divide those joints into different categories."},{"Start":"01:35.315 ","End":"01:37.775","Text":"The first is fibrous,"},{"Start":"01:37.775 ","End":"01:42.440","Text":"and they form these sutures that are in the skull."},{"Start":"01:42.440 ","End":"01:44.000","Text":"As we\u0027ve mentioned before,"},{"Start":"01:44.000 ","End":"01:46.685","Text":"the fibrous joints are immovable."},{"Start":"01:46.685 ","End":"01:49.840","Text":"They don\u0027t move one with respect to the other."},{"Start":"01:49.840 ","End":"01:56.075","Text":"Another joint is a cartilaginous joint."},{"Start":"01:56.075 ","End":"02:01.550","Text":"That means that it has cartilage in it and they are semi movable."},{"Start":"02:01.550 ","End":"02:03.560","Text":"They do bend and somewhat you know that"},{"Start":"02:03.560 ","End":"02:07.775","Text":"your back moves and the discs that are in your back,"},{"Start":"02:07.775 ","End":"02:13.370","Text":"in your vertebra are made of cartilage and so they\u0027re cartilaginous."},{"Start":"02:13.370 ","End":"02:17.880","Text":"Then there\u0027s another joint called a synovial joint."},{"Start":"02:17.880 ","End":"02:20.340","Text":"That\u0027s the joint you usually think about."},{"Start":"02:20.340 ","End":"02:27.535","Text":"It\u0027s the kind of joint in which there is free movement between the different bones."},{"Start":"02:27.535 ","End":"02:32.270","Text":"There\u0027s a large area that contains a fluid,"},{"Start":"02:32.270 ","End":"02:33.965","Text":"as we\u0027ll see in a bit,"},{"Start":"02:33.965 ","End":"02:36.740","Text":"that allows the bones to be lubricated,"},{"Start":"02:36.740 ","End":"02:38.705","Text":"one with respect to the other."},{"Start":"02:38.705 ","End":"02:41.885","Text":"We\u0027ll get back to this in a bit."},{"Start":"02:41.885 ","End":"02:49.325","Text":"Let\u0027s now look at the sutures in more detail that we\u0027ve mentioned before."},{"Start":"02:49.325 ","End":"02:54.145","Text":"They\u0027re held together with very short interlocking fibers,"},{"Start":"02:54.145 ","End":"02:58.830","Text":"these fibers that are made of fibrous material,"},{"Start":"02:58.830 ","End":"03:03.070","Text":"and then the bones themselves also interlock,"},{"Start":"03:03.070 ","End":"03:06.005","Text":"and those are found in the skull."},{"Start":"03:06.005 ","End":"03:11.555","Text":"Next we\u0027re going to look at things that are called syndesmoses joints."},{"Start":"03:11.555 ","End":"03:16.590","Text":"These are joints in which we have contact between different bones."},{"Start":"03:16.590 ","End":"03:21.080","Text":"For instance, in the ankle between the tibia and fibula,"},{"Start":"03:21.080 ","End":"03:23.420","Text":"these bones come together."},{"Start":"03:23.420 ","End":"03:27.350","Text":"They have to move a bit with respect to each other, but not a lot."},{"Start":"03:27.350 ","End":"03:30.820","Text":"They\u0027re held together by ligaments."},{"Start":"03:30.820 ","End":"03:34.820","Text":"This fibrous tissue that\u0027s between them can vary in length,"},{"Start":"03:34.820 ","End":"03:41.200","Text":"but it\u0027s longer than in the sutures that are in the skull."},{"Start":"03:41.200 ","End":"03:45.510","Text":"Next we have gomphosis."},{"Start":"03:45.920 ","End":"03:49.545","Text":"You know that in your skull,"},{"Start":"03:49.545 ","End":"03:53.780","Text":"you have teeth that are embedded in"},{"Start":"03:53.780 ","End":"03:59.492","Text":"the bone of the skull and there\u0027s something called a periodontal ligament,"},{"Start":"03:59.492 ","End":"04:01.175","Text":"we\u0027ll come back to that maybe,"},{"Start":"04:01.175 ","End":"04:07.670","Text":"in which there is a connection between the tooth and the bone which is below it."},{"Start":"04:07.670 ","End":"04:10.965","Text":"It\u0027s a pagan socket joint,"},{"Start":"04:10.965 ","End":"04:13.685","Text":"and it doesn\u0027t move,"},{"Start":"04:13.685 ","End":"04:15.575","Text":"at least not very much."},{"Start":"04:15.575 ","End":"04:17.899","Text":"Now going back to the sutures,"},{"Start":"04:17.899 ","End":"04:21.620","Text":"they\u0027re found between these flat plate-like bones of the skull,"},{"Start":"04:21.620 ","End":"04:24.230","Text":"and they have these short fibers of connective tissue,"},{"Start":"04:24.230 ","End":"04:28.655","Text":"as we mentioned, and they only allow very little movement, and in fact,"},{"Start":"04:28.655 ","End":"04:30.350","Text":"after the age of 20,"},{"Start":"04:30.350 ","End":"04:34.835","Text":"there\u0027s essentially no movement there, pretty much immobile."},{"Start":"04:34.835 ","End":"04:37.535","Text":"Now what about the syndesmoses?"},{"Start":"04:37.535 ","End":"04:44.105","Text":"The syndesmoses, it holds the bones together with this band of connective tissue,"},{"Start":"04:44.105 ","End":"04:48.035","Text":"say for instance in the forearm or in the leg,"},{"Start":"04:48.035 ","End":"04:50.015","Text":"as we mentioned a little bit earlier,"},{"Start":"04:50.015 ","End":"04:55.165","Text":"are connected with his band of tissue and it provides very strong stabilization,"},{"Start":"04:55.165 ","End":"04:58.694","Text":"but at the same time, dynamics support."},{"Start":"04:58.694 ","End":"05:03.230","Text":"That means that they can move one with respect to the other just a bit."},{"Start":"05:03.230 ","End":"05:08.630","Text":"An example of that would be the joint between the radius and the ulna and the forearm,"},{"Start":"05:08.630 ","End":"05:12.995","Text":"and the joint between the tibia and the fibula that are in the leg,"},{"Start":"05:12.995 ","End":"05:14.825","Text":"as we mentioned earlier."},{"Start":"05:14.825 ","End":"05:19.295","Text":"Let\u0027s now look in more detail at the gomphosis, that is,"},{"Start":"05:19.295 ","End":"05:23.120","Text":"the teeth and how there are embedded in"},{"Start":"05:23.120 ","End":"05:27.815","Text":"the skull or sometimes in the mandible if we\u0027re talking about the lower teeth."},{"Start":"05:27.815 ","End":"05:33.300","Text":"In that case, there\u0027s no movement in there in this pagan socket joint,"},{"Start":"05:33.300 ","End":"05:38.330","Text":"but the teeth are connected by some connective tissue,"},{"Start":"05:38.330 ","End":"05:43.745","Text":"and that connective tissue is a ligament called the periodontal ligament."},{"Start":"05:43.745 ","End":"05:50.210","Text":"This is the only type of joint that we classify as a joint in which it\u0027s not a bone,"},{"Start":"05:50.210 ","End":"05:53.675","Text":"rather it\u0027s a tooth that joins another bone."},{"Start":"05:53.675 ","End":"05:58.130","Text":"Next, let\u0027s move on to the cartilaginous joints."},{"Start":"05:58.130 ","End":"06:02.105","Text":"These are the bones that are connected entirely by cartilage."},{"Start":"06:02.105 ","End":"06:06.080","Text":"They could be either fibrocartilage or hyaline, and where do we see them?"},{"Start":"06:06.080 ","End":"06:08.210","Text":"So, for instance, when the bone grows,"},{"Start":"06:08.210 ","End":"06:11.300","Text":"remember there\u0027s this epiphyseal plate"},{"Start":"06:11.300 ","End":"06:14.810","Text":"which forms and that has cartilage in it that separates"},{"Start":"06:14.810 ","End":"06:17.840","Text":"the end of the bone from the longer part of"},{"Start":"06:17.840 ","End":"06:22.460","Text":"the bone and also the sternum which is in front of our chest,"},{"Start":"06:22.460 ","End":"06:25.625","Text":"is connected to the ribs in some of the cases,"},{"Start":"06:25.625 ","End":"06:30.545","Text":"with this cartilaginous joint."},{"Start":"06:30.545 ","End":"06:33.275","Text":"It allows some movement between the bones,"},{"Start":"06:33.275 ","End":"06:37.055","Text":"but this movement is less than in the synovial joint,"},{"Start":"06:37.055 ","End":"06:41.360","Text":"that is, say in the arms and legs."},{"Start":"06:41.360 ","End":"06:46.085","Text":"There are 2 different types of joints."},{"Start":"06:46.085 ","End":"06:49.320","Text":"They are in this category,"},{"Start":"06:49.320 ","End":"06:52.747","Text":"and there are the synchondrosis,"},{"Start":"06:52.747 ","End":"06:57.260","Text":"those are the bones that are completely joined by hyaline and cartilage, for example,"},{"Start":"06:57.260 ","End":"07:01.400","Text":"the sternocostal joint that unites the ribs and"},{"Start":"07:01.400 ","End":"07:06.440","Text":"the sternum as we mentioned before and there are the symphysis."},{"Start":"07:06.440 ","End":"07:10.730","Text":"Those are bones that are connected by a fibrocartilage and examples of"},{"Start":"07:10.730 ","End":"07:16.240","Text":"that would be in the vertebrae that are between the disks."},{"Start":"07:16.240 ","End":"07:20.870","Text":"Lastly now look at the synovial joints."},{"Start":"07:20.870 ","End":"07:24.770","Text":"The synovial joints have the most movement as we mentioned before,"},{"Start":"07:24.770 ","End":"07:30.710","Text":"and they contain this fluid, the synovial fluid,"},{"Start":"07:30.710 ","End":"07:32.135","Text":"which is in the cavity,"},{"Start":"07:32.135 ","End":"07:34.325","Text":"which is the lubrication,"},{"Start":"07:34.325 ","End":"07:42.200","Text":"and it provides the joint lubrication so that the bones can move freely,"},{"Start":"07:42.200 ","End":"07:43.900","Text":"one with respect to the other."},{"Start":"07:43.900 ","End":"07:46.565","Text":"We have that particularly in the limb,"},{"Start":"07:46.565 ","End":"07:49.205","Text":"say the knees, the elbows, the shoulders,"},{"Start":"07:49.205 ","End":"07:52.670","Text":"but this movement has to also be protected in"},{"Start":"07:52.670 ","End":"07:56.420","Text":"the sense that the bones shouldn\u0027t be able to move out of"},{"Start":"07:56.420 ","End":"08:00.920","Text":"a particular area and they\u0027re covered therefore with"},{"Start":"08:00.920 ","End":"08:06.245","Text":"this hyaline cartilage as a lubricant as well."},{"Start":"08:06.245 ","End":"08:07.805","Text":"But in addition to that,"},{"Start":"08:07.805 ","End":"08:12.110","Text":"there\u0027s this structure around the entire thing."},{"Start":"08:12.110 ","End":"08:14.600","Text":"There\u0027s a capsule that\u0027s composed of"},{"Start":"08:14.600 ","End":"08:17.855","Text":"connective tissues and that allows movement of the joints,"},{"Start":"08:17.855 ","End":"08:21.795","Text":"but doesn\u0027t allow dislocation."},{"Start":"08:21.795 ","End":"08:26.690","Text":"Articular capsules may also possess accessory ligaments that holds"},{"Start":"08:26.690 ","End":"08:32.309","Text":"the bones together that we see here in purple on the outside."}],"ID":30258},{"Watched":false,"Name":"Functional Classification of Joints","Duration":"7m 6s","ChapterTopicVideoID":28719,"CourseChapterTopicPlaylistID":286921,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.200 ","End":"00:03.990","Text":"We\u0027ve been speaking about joints"},{"Start":"00:03.990 ","End":"00:09.120","Text":"that are the places where bones meet and where they articulate,"},{"Start":"00:09.120 ","End":"00:12.450","Text":"and we\u0027re going to continue our discussion of the classification"},{"Start":"00:12.450 ","End":"00:16.484","Text":"of these joints which is based now on function."},{"Start":"00:16.484 ","End":"00:19.785","Text":"They are divided into 3 different categories."},{"Start":"00:19.785 ","End":"00:22.740","Text":"There\u0027s the synarthrosis,"},{"Start":"00:22.740 ","End":"00:25.170","Text":"that\u0027s the immovable joints like the sutures,"},{"Start":"00:25.170 ","End":"00:28.155","Text":"the gomphosis, and synchondrosis."},{"Start":"00:28.155 ","End":"00:33.240","Text":"Remember, those have a structural characteristic."},{"Start":"00:33.240 ","End":"00:35.220","Text":"Yes, and they\u0027re immovable, for instance,"},{"Start":"00:35.220 ","End":"00:39.570","Text":"in the skull and that\u0027s what the synarthrosis are."},{"Start":"00:39.570 ","End":"00:41.520","Text":"Then there\u0027s the amphiarthrosis."},{"Start":"00:41.520 ","End":"00:43.785","Text":"Those are cartilaginous,"},{"Start":"00:43.785 ","End":"00:46.235","Text":"they have cartilage and they\u0027re slightly movable."},{"Start":"00:46.235 ","End":"00:48.800","Text":"For instance, in the pubis, yes,"},{"Start":"00:48.800 ","End":"00:52.525","Text":"that\u0027s where the bottom of the pelvic bone."},{"Start":"00:52.525 ","End":"00:56.150","Text":"Then we have another kind that is a joint that"},{"Start":"00:56.150 ","End":"00:59.960","Text":"allows for free movement in the synovial joints,"},{"Start":"00:59.960 ","End":"01:02.435","Text":"which are called diarthrosis."},{"Start":"01:02.435 ","End":"01:05.060","Text":"Those are the synovial joints that are freely movable,"},{"Start":"01:05.060 ","End":"01:07.505","Text":"for instance, in the shoulder."},{"Start":"01:07.505 ","End":"01:11.510","Text":"Now let\u0027s look at the movement at these synovial joints."},{"Start":"01:11.510 ","End":"01:16.163","Text":"The movements now also are classified in different ways;"},{"Start":"01:16.163 ","End":"01:18.530","Text":"gliding, angular motion,"},{"Start":"01:18.530 ","End":"01:21.455","Text":"rotational motion, and special movement."},{"Start":"01:21.455 ","End":"01:28.695","Text":"Let\u0027s see how these bones at the various joints move 1 with respect to the other."},{"Start":"01:28.695 ","End":"01:31.430","Text":"They can move in a gliding way."},{"Start":"01:31.430 ","End":"01:32.810","Text":"That occurs, let\u0027s say,"},{"Start":"01:32.810 ","End":"01:34.835","Text":"as a relatively flat bone,"},{"Start":"01:34.835 ","End":"01:36.905","Text":"surface moves past another."},{"Start":"01:36.905 ","End":"01:39.740","Text":"That can be say in the foot and the ankle,"},{"Start":"01:39.740 ","End":"01:43.370","Text":"where these bones move slightly in the ankle,"},{"Start":"01:43.370 ","End":"01:47.930","Text":"one with respect to the other as our foot flexes and these"},{"Start":"01:47.930 ","End":"01:53.060","Text":"allow movement in any direction along the plane as you can see over here on the right."},{"Start":"01:53.060 ","End":"01:56.840","Text":"They can go up and down left and right diagonally as seen and so on."},{"Start":"01:56.840 ","End":"01:57.980","Text":"These are gliding movements."},{"Start":"01:57.980 ","End":"02:00.349","Text":"They provide very little rotation,"},{"Start":"02:00.349 ","End":"02:03.650","Text":"but they do allow enough movement,"},{"Start":"02:03.650 ","End":"02:04.850","Text":"say in the ankle,"},{"Start":"02:04.850 ","End":"02:06.595","Text":"as we mentioned before."},{"Start":"02:06.595 ","End":"02:09.650","Text":"Then we have angular movement."},{"Start":"02:09.650 ","End":"02:11.660","Text":"For instance, that if we have a leg,"},{"Start":"02:11.660 ","End":"02:16.705","Text":"there is an angle which is formed when we bend our leg."},{"Start":"02:16.705 ","End":"02:19.850","Text":"That would be called angular movement."},{"Start":"02:19.850 ","End":"02:23.075","Text":"That can be classified in different ways as well."},{"Start":"02:23.075 ","End":"02:27.635","Text":"There is flexion which is bending when the angle of the bone"},{"Start":"02:27.635 ","End":"02:32.825","Text":"decreases like moving the forearm upward at the elbow or the flexing of the leg,"},{"Start":"02:32.825 ","End":"02:34.490","Text":"as you can see over here."},{"Start":"02:34.490 ","End":"02:36.770","Text":"Or of course, we can have the opposite movement,"},{"Start":"02:36.770 ","End":"02:39.930","Text":"we can extend the leg or the arm or whatever."},{"Start":"02:39.930 ","End":"02:43.535","Text":"It\u0027s the opposite when the angle increases."},{"Start":"02:43.535 ","End":"02:47.630","Text":"Then we also have something which could be hyperextension."},{"Start":"02:47.630 ","End":"02:50.690","Text":"It\u0027s not only within the normal movement,"},{"Start":"02:50.690 ","End":"02:55.460","Text":"but sometimes we can extend past the regular anatomical position."},{"Start":"02:55.460 ","End":"02:58.385","Text":"A good example of that is in the neck."},{"Start":"02:58.385 ","End":"03:03.140","Text":"When we move our neck backwards to look up,"},{"Start":"03:03.140 ","End":"03:08.045","Text":"then our neck is extended beyond where it normally is,"},{"Start":"03:08.045 ","End":"03:10.085","Text":"but still that\u0027s okay."},{"Start":"03:10.085 ","End":"03:14.480","Text":"Now, this angular movement can also be divided in a different way."},{"Start":"03:14.480 ","End":"03:17.630","Text":"We can say that we have abduction."},{"Start":"03:17.630 ","End":"03:20.500","Text":"That\u0027s when a bone moves away from the midline of the body."},{"Start":"03:20.500 ","End":"03:23.315","Text":"If the midline of the body is through here,"},{"Start":"03:23.315 ","End":"03:27.830","Text":"we have an angle in which we\u0027re moving the leg away from it."},{"Start":"03:27.830 ","End":"03:33.290","Text":"That is say, raising the arm from the shoulder or moving the leg as you see here."},{"Start":"03:33.290 ","End":"03:36.440","Text":"Then we have something else, the abduction,"},{"Start":"03:36.440 ","End":"03:40.670","Text":"which would be the opposite movements moving towards the midline of the body."},{"Start":"03:40.670 ","End":"03:46.630","Text":"For example, moving them inward as it\u0027s shown here in the figure."},{"Start":"03:46.630 ","End":"03:50.195","Text":"Then we can turn some of our limbs as well."},{"Start":"03:50.195 ","End":"03:53.255","Text":"Those would be called circumduction,"},{"Start":"03:53.255 ","End":"03:59.075","Text":"like circle like movement of a limb in a circular motion like moving the arm around."},{"Start":"03:59.075 ","End":"04:03.105","Text":"Yes, like in a windmill fashion that you can see here."},{"Start":"04:03.105 ","End":"04:05.360","Text":"Of course, there\u0027s also rotation,"},{"Start":"04:05.360 ","End":"04:08.615","Text":"which is a little bit different than moving in a circle."},{"Start":"04:08.615 ","End":"04:13.475","Text":"The rotation is moving around a longitudinal axis,"},{"Start":"04:13.475 ","End":"04:16.835","Text":"and the movement is around that."},{"Start":"04:16.835 ","End":"04:20.900","Text":"We could have a rotation of the foot itself,"},{"Start":"04:20.900 ","End":"04:23.615","Text":"or we could have medial rotation,"},{"Start":"04:23.615 ","End":"04:29.380","Text":"which will be moving around the midline of the body itself."},{"Start":"04:29.380 ","End":"04:34.535","Text":"We could have lateral rotation moving away from the body,"},{"Start":"04:34.535 ","End":"04:39.710","Text":"or we could have internal rotation moving towards the body."},{"Start":"04:39.710 ","End":"04:41.765","Text":"Now addition to all that,"},{"Start":"04:41.765 ","End":"04:45.620","Text":"we have some special movements that we"},{"Start":"04:45.620 ","End":"04:50.150","Text":"can\u0027t classify in the previous kinds of classifications."},{"Start":"04:50.150 ","End":"04:52.970","Text":"Those would be, for instance,"},{"Start":"04:52.970 ","End":"04:54.380","Text":"turning of our ankle,"},{"Start":"04:54.380 ","End":"04:56.210","Text":"we can turn it in."},{"Start":"04:56.210 ","End":"05:00.950","Text":"Let\u0027s say if we sprain one of the lateral ligaments that we turn our foot in,"},{"Start":"05:00.950 ","End":"05:02.689","Text":"that would be called an inversion."},{"Start":"05:02.689 ","End":"05:06.140","Text":"Whereas if it turned out, this is the same foot,"},{"Start":"05:06.140 ","End":"05:08.570","Text":"notice the large big toe"},{"Start":"05:08.570 ","End":"05:11.275","Text":"is on the right knee to them if it\u0027s turned in the other direction,"},{"Start":"05:11.275 ","End":"05:13.640","Text":"we might be spraining a ligament on the other side."},{"Start":"05:13.640 ","End":"05:16.040","Text":"That would be called an eversion."},{"Start":"05:16.040 ","End":"05:18.650","Text":"It\u0027s an opposite of inversion."},{"Start":"05:18.650 ","End":"05:23.420","Text":"The soles would then would be moved outward away from the midline of the body."},{"Start":"05:23.420 ","End":"05:27.560","Text":"In addition, there are other special movements like protraction,"},{"Start":"05:27.560 ","End":"05:30.640","Text":"is the anterior movement of bone in the horizontal plane."},{"Start":"05:30.640 ","End":"05:35.150","Text":"We can have protraction and retraction"},{"Start":"05:35.150 ","End":"05:39.530","Text":"moves a joint back into position after protraction."},{"Start":"05:39.530 ","End":"05:42.530","Text":"You can move the mandible, for instance,"},{"Start":"05:42.530 ","End":"05:45.110","Text":"you can move your lower jaw backwards and"},{"Start":"05:45.110 ","End":"05:48.880","Text":"forwards and that would be retraction or protraction."},{"Start":"05:48.880 ","End":"05:52.330","Text":"You could have elevation that would be moving it up,"},{"Start":"05:52.330 ","End":"05:54.770","Text":"or you could have depression moving it down."},{"Start":"05:54.770 ","End":"05:58.160","Text":"The mandible, they can move every which way."},{"Start":"05:58.160 ","End":"06:02.035","Text":"Other kinds of special movements would be"},{"Start":"06:02.035 ","End":"06:07.385","Text":"dorsiflexion and plantar flexion. What are those?"},{"Start":"06:07.385 ","End":"06:13.350","Text":"That would be when your ankle bends up would be dorsiflexion or it bends down,"},{"Start":"06:13.350 ","End":"06:17.985","Text":"let\u0027s say when you\u0027re standing on your toes going down."},{"Start":"06:17.985 ","End":"06:20.345","Text":"There are terms for all of these things."},{"Start":"06:20.345 ","End":"06:25.070","Text":"There\u0027s supination, that\u0027s movement of the radius and the ulna bones of"},{"Start":"06:25.070 ","End":"06:29.780","Text":"the forearms so that the palm faces forward is supination."},{"Start":"06:29.780 ","End":"06:36.005","Text":"The opposite of that is pronation when your palm faces downward, really."},{"Start":"06:36.005 ","End":"06:42.065","Text":"In addition, we have some other kind of movements between the thumb and the forefinger."},{"Start":"06:42.065 ","End":"06:49.490","Text":"Yes. That is called opposition and that allows us to grab and hold up objects."},{"Start":"06:49.490 ","End":"06:56.345","Text":"Primates are special organisms in that we have the ability to have"},{"Start":"06:56.345 ","End":"07:05.740","Text":"opposition between our thumb and the rest of our hand and that allows us to grab things."}],"ID":30259},{"Watched":false,"Name":"Functional Classification of Joints Continued","Duration":"4m 59s","ChapterTopicVideoID":28720,"CourseChapterTopicPlaylistID":286921,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.860","Text":"Hi, Welcome back. Let\u0027s continue our discussion now of our joints"},{"Start":"00:04.860 ","End":"00:09.645","Text":"by looking at different types of synovial joints."},{"Start":"00:09.645 ","End":"00:12.330","Text":"Remember, synovial joints are these joints that we have in"},{"Start":"00:12.330 ","End":"00:16.365","Text":"our limbs that allow us to move every which way."},{"Start":"00:16.365 ","End":"00:21.735","Text":"They actually differ these joints in a more subtle way."},{"Start":"00:21.735 ","End":"00:23.715","Text":"Some of them allow gliding,"},{"Start":"00:23.715 ","End":"00:30.103","Text":"others allow a hinge motion, others pivots,"},{"Start":"00:30.103 ","End":"00:34.155","Text":"others are condyloid,"},{"Start":"00:34.155 ","End":"00:39.080","Text":"and saddle movement and ball-and- socket."},{"Start":"00:39.080 ","End":"00:41.335","Text":"So let\u0027s see each of them."},{"Start":"00:41.335 ","End":"00:43.700","Text":"Now, the gliding 1s, for instance,"},{"Start":"00:43.700 ","End":"00:46.625","Text":"would be in our carpal, in our hand."},{"Start":"00:46.625 ","End":"00:50.060","Text":"These joints can move slightly past each other."},{"Start":"00:50.060 ","End":"00:51.970","Text":"The hinged joint,"},{"Start":"00:51.970 ","End":"00:57.890","Text":"would be more in our elbow."},{"Start":"00:57.890 ","End":"01:00.455","Text":"That our arm moves more like a hinge."},{"Start":"01:00.455 ","End":"01:07.835","Text":"The pivot joint would also in a little bit allow us to turn our arm around."},{"Start":"01:07.835 ","End":"01:13.395","Text":"The condyloid is a special kind of a joint."},{"Start":"01:13.395 ","End":"01:17.720","Text":"It allows movement in different directions."},{"Start":"01:17.720 ","End":"01:22.430","Text":"Something that allows our hand to change its shape and then we have"},{"Start":"01:22.430 ","End":"01:27.860","Text":"in these bones that are in our carpals, metacarpals."},{"Start":"01:27.860 ","End":"01:33.815","Text":"Then we have a saddle type bone in which the 2 different sides of the bone look like."},{"Start":"01:33.815 ","End":"01:37.640","Text":"Saddles it\u0027s a joint that allows us to move in"},{"Start":"01:37.640 ","End":"01:42.530","Text":"a particular direction and we have them in the joints in our hands as well."},{"Start":"01:42.530 ","End":"01:46.490","Text":"Of course there\u0027s a ball-and-socket that is"},{"Start":"01:46.490 ","End":"01:52.265","Text":"more of the thing that we have in our shoulder and also in our hip."},{"Start":"01:52.265 ","End":"01:58.210","Text":"The joint shape obviously affects the movement that it permits."},{"Start":"01:58.210 ","End":"02:01.610","Text":"Let\u0027s look at these a little bit more detail."},{"Start":"02:01.610 ","End":"02:09.170","Text":"The gliding movement in the carpals involve these articulating surfaces that are flat,"},{"Start":"02:09.170 ","End":"02:14.330","Text":"but are slightly curved at the ends and they allow for gliding movements."},{"Start":"02:14.330 ","End":"02:17.000","Text":"The range of motion is very limited, of course,"},{"Start":"02:17.000 ","End":"02:20.650","Text":"but the hand does change its shape somewhat."},{"Start":"02:20.650 ","End":"02:24.200","Text":"Those are the case also in the foot,"},{"Start":"02:24.200 ","End":"02:26.750","Text":"which can also change some shape and we have"},{"Start":"02:26.750 ","End":"02:30.800","Text":"some movement similar to that in some of the vertebra."},{"Start":"02:30.800 ","End":"02:36.835","Text":"The hinge joints on the other hand are slightly rounded at the bottom of them."},{"Start":"02:36.835 ","End":"02:41.135","Text":"There\u0027s a hollow on the other end that they move into."},{"Start":"02:41.135 ","End":"02:46.265","Text":"One bone remains stationary like the hinge of a door and the other one moves."},{"Start":"02:46.265 ","End":"02:50.975","Text":"Here we have humerus is not moving,"},{"Start":"02:50.975 ","End":"02:56.030","Text":"but the radius and ulna do move with respect to it."},{"Start":"02:56.030 ","End":"03:00.890","Text":"We also have just pivot joints so you know that you can turn your head for instance,"},{"Start":"03:00.890 ","End":"03:08.390","Text":"and we have these 2 joints called atlas and axis there that allow us to move"},{"Start":"03:08.390 ","End":"03:15.800","Text":"our skull in various directions relative to our vertebra."},{"Start":"03:15.800 ","End":"03:20.600","Text":"Our head therefore can move back and forth, right and left."},{"Start":"03:20.600 ","End":"03:23.750","Text":"We have something similar in the joint of our wrist that allows"},{"Start":"03:23.750 ","End":"03:27.410","Text":"the palm of the hand to be turned forward and backward."},{"Start":"03:27.410 ","End":"03:31.070","Text":"That\u0027s also a pivot joints."},{"Start":"03:31.070 ","End":"03:36.035","Text":"Then we have these condyloid joints that I mentioned earlier."},{"Start":"03:36.035 ","End":"03:41.660","Text":"Sometimes they\u0027re called ellipsoidal because they have like an oval shape."},{"Start":"03:41.660 ","End":"03:44.870","Text":"This is we have these particularly in our fingers,"},{"Start":"03:44.870 ","End":"03:49.805","Text":"where one end of the bone fits into another oval shaped area on the,"},{"Start":"03:49.805 ","End":"03:52.715","Text":"it\u0027s a little bit hollowed on the other side of a bone,"},{"Start":"03:52.715 ","End":"03:54.520","Text":"on the opposing bone."},{"Start":"03:54.520 ","End":"03:58.190","Text":"This is particularly the case as we mentioned in the fingers,"},{"Start":"03:58.190 ","End":"04:00.500","Text":"but also in the wrist."},{"Start":"04:00.500 ","End":"04:08.700","Text":"The saddle joints are somewhat similar but they allow movement on only one direction."},{"Start":"04:09.530 ","End":"04:14.492","Text":"They\u0027re like condyloid joints which have very little motion."},{"Start":"04:14.492 ","End":"04:17.000","Text":"These allow a greater range of motion,"},{"Start":"04:17.000 ","End":"04:19.070","Text":"but it\u0027s only in a particular direction,"},{"Start":"04:19.070 ","End":"04:22.160","Text":"back and forth, up and down and so on."},{"Start":"04:22.160 ","End":"04:27.440","Text":"Finally, we have the ball-and-socket that we talked about here in the hip,"},{"Start":"04:27.440 ","End":"04:28.880","Text":"but also in the shoulder,"},{"Start":"04:28.880 ","End":"04:32.810","Text":"that presents a rounded ball-like end of a bone."},{"Start":"04:32.810 ","End":"04:37.995","Text":"You can see here that fits into a cuplike socket of another bone."},{"Start":"04:37.995 ","End":"04:40.310","Text":"The distal bonus capable of motion."},{"Start":"04:40.310 ","End":"04:46.250","Text":"Distal bone down here is capable of motion around an indefinite number of axes."},{"Start":"04:46.250 ","End":"04:50.795","Text":"It can move forward, backwards around anyway we need to,"},{"Start":"04:50.795 ","End":"04:58.710","Text":"and we have this in our shoulder and hips as we\u0027ve mentioned earlier."}],"ID":30260}],"Thumbnail":null,"ID":286921},{"Name":"Muscle Contraction and Locomotion","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Types of Muscles","Duration":"5m 53s","ChapterTopicVideoID":28729,"CourseChapterTopicPlaylistID":286922,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.940","Text":"I\u0027m glad you\u0027re back now to discuss muscle contraction and locomotion."},{"Start":"00:05.940 ","End":"00:09.689","Text":"We\u0027ve been discussing bones and we\u0027d been discussing joints."},{"Start":"00:09.689 ","End":"00:13.740","Text":"But of course, these bones"},{"Start":"00:13.740 ","End":"00:19.380","Text":"move one with respect to the other and they are moved by muscles."},{"Start":"00:19.380 ","End":"00:21.210","Text":"In the coming videos,"},{"Start":"00:21.210 ","End":"00:24.840","Text":"we\u0027re going to discuss how muscle cells work,"},{"Start":"00:24.840 ","End":"00:28.815","Text":"and of course, they are specialized for contraction."},{"Start":"00:28.815 ","End":"00:33.510","Text":"If you look at the body that contains muscles in this diagram,"},{"Start":"00:33.510 ","End":"00:38.405","Text":"it will look quite familiar to you because this is what there is just under the skin."},{"Start":"00:38.405 ","End":"00:42.470","Text":"That\u0027s really what forms the outer structure of our body."},{"Start":"00:42.470 ","End":"00:45.150","Text":"As you can see, the body is made up of many,"},{"Start":"00:45.150 ","End":"00:53.570","Text":"many different muscles that pull in various directions to make us move as we do."},{"Start":"00:53.570 ","End":"00:56.300","Text":"In some cases, like in the hand, for instance,"},{"Start":"00:56.300 ","End":"01:00.770","Text":"we have a very large number of muscles that control,"},{"Start":"01:00.770 ","End":"01:04.610","Text":"via tendons, the movement of our fingers."},{"Start":"01:04.610 ","End":"01:07.745","Text":"But what we\u0027re going to do here now is discuss"},{"Start":"01:07.745 ","End":"01:11.630","Text":"the muscle cells themselves and see how they work."},{"Start":"01:11.630 ","End":"01:14.160","Text":"They make up between 40 and 50"},{"Start":"01:14.160 ","End":"01:17.280","Text":"percent of human body weights so clearly they\u0027re important."},{"Start":"01:17.280 ","End":"01:21.125","Text":"They facilitate not only movement but also respiration."},{"Start":"01:21.125 ","End":"01:27.005","Text":"Because our diaphragm moves up and down allowing us to breathe or digestion."},{"Start":"01:27.005 ","End":"01:28.190","Text":"Because as we\u0027ll see,"},{"Start":"01:28.190 ","End":"01:33.830","Text":"they\u0027re specialized muscles that are inside our bodies that"},{"Start":"01:33.830 ","End":"01:39.755","Text":"make up parts of our intestine that move food through our digestive system."},{"Start":"01:39.755 ","End":"01:42.830","Text":"There is heat production because that\u0027s"},{"Start":"01:42.830 ","End":"01:47.360","Text":"a byproduct of the muscles and the moving of the muscles."},{"Start":"01:47.360 ","End":"01:50.270","Text":"Since they make up so much of the body weight,"},{"Start":"01:50.270 ","End":"01:55.435","Text":"to large extent, that they are important for regulating the body heat."},{"Start":"01:55.435 ","End":"01:58.850","Text":"Now let\u0027s look at the various characteristics"},{"Start":"01:58.850 ","End":"02:02.390","Text":"of muscles and to try to understand how they work."},{"Start":"02:02.390 ","End":"02:06.650","Text":"Of course, they can be excited to contract."},{"Start":"02:06.650 ","End":"02:10.250","Text":"They respond by stimulation, by membrane potentials."},{"Start":"02:10.250 ","End":"02:14.030","Text":"They\u0027re innervated so that they move when they need to be."},{"Start":"02:14.030 ","End":"02:16.820","Text":"They can, of course, extend,"},{"Start":"02:16.820 ","End":"02:20.295","Text":"so after they\u0027ve contracted, they can extend."},{"Start":"02:20.295 ","End":"02:24.240","Text":"In addition, the muscles are elastic."},{"Start":"02:24.240 ","End":"02:27.415","Text":"That is, they can stretch,"},{"Start":"02:27.415 ","End":"02:30.440","Text":"they can become a little bit longer,"},{"Start":"02:30.440 ","End":"02:33.500","Text":"and then return to normal length after stretching."},{"Start":"02:33.500 ","End":"02:34.940","Text":"We know that after exercise,"},{"Start":"02:34.940 ","End":"02:37.595","Text":"we do that stretching."},{"Start":"02:37.595 ","End":"02:39.680","Text":"Muscles can contract,"},{"Start":"02:39.680 ","End":"02:42.280","Text":"they\u0027re excitable by nerves,"},{"Start":"02:42.280 ","End":"02:45.395","Text":"they can extend in addition to contract,"},{"Start":"02:45.395 ","End":"02:47.210","Text":"and they are elastic."},{"Start":"02:47.210 ","End":"02:51.740","Text":"Now, there are different forms of muscle,"},{"Start":"02:51.740 ","End":"02:55.925","Text":"and let\u0027s start by looking at skeletal muscle."},{"Start":"02:55.925 ","End":"03:01.250","Text":"Skeletal muscle is the muscle that we have in our extremities."},{"Start":"03:01.250 ","End":"03:03.350","Text":"Sometimes it\u0027s called fast muscle."},{"Start":"03:03.350 ","End":"03:05.765","Text":"It also controls locomotion,"},{"Start":"03:05.765 ","End":"03:09.214","Text":"and of course, it\u0027s consciously controlled."},{"Start":"03:09.214 ","End":"03:11.390","Text":"That is, it\u0027s a voluntary muscle,"},{"Start":"03:11.390 ","End":"03:17.705","Text":"so we can decide when to move it and when not to move it and how to move it."},{"Start":"03:17.705 ","End":"03:23.185","Text":"Now, if we look at it in a microscopic way that you can see here, there\u0027s a pattern."},{"Start":"03:23.185 ","End":"03:27.020","Text":"You can see that there are these stripes that we see in"},{"Start":"03:27.020 ","End":"03:31.400","Text":"a microscope if we look at a sample of muscle and"},{"Start":"03:31.400 ","End":"03:34.790","Text":"it\u0027s called striated sometimes because of"},{"Start":"03:34.790 ","End":"03:39.575","Text":"this regular arrangement of contractile protein as it turns out."},{"Start":"03:39.575 ","End":"03:42.650","Text":"These contractile proteins are called actin and"},{"Start":"03:42.650 ","End":"03:46.645","Text":"myosin will go into the details of them very soon."},{"Start":"03:46.645 ","End":"03:52.400","Text":"These proteins is going to turn out to actin and myosin interact with each other."},{"Start":"03:52.400 ","End":"03:57.110","Text":"It\u0027s that interaction and as we\u0027ll see actually they\u0027re sliding past one another."},{"Start":"03:57.110 ","End":"04:00.544","Text":"That is going to cause the muscle to contract."},{"Start":"04:00.544 ","End":"04:05.600","Text":"Now as you know, almost all cells have only 1 nucleus in them."},{"Start":"04:05.600 ","End":"04:09.214","Text":"Interestingly, muscle cells,"},{"Start":"04:09.214 ","End":"04:11.480","Text":"at least skeletal muscle cells,"},{"Start":"04:11.480 ","End":"04:17.495","Text":"have multiple nuclei in them because in their formation they fuse."},{"Start":"04:17.495 ","End":"04:20.270","Text":"That\u0027s the case for skeletal muscle."},{"Start":"04:20.270 ","End":"04:23.030","Text":"Now, let\u0027s look at smooth muscle."},{"Start":"04:23.030 ","End":"04:29.150","Text":"Smooth muscle is the muscle that\u0027s located in the walls of the intestines of stomach,"},{"Start":"04:29.150 ","End":"04:33.325","Text":"the urinary bladder, things that we do not have control over."},{"Start":"04:33.325 ","End":"04:36.680","Text":"They have no striations,"},{"Start":"04:36.680 ","End":"04:39.920","Text":"as you can see in this micrograph."},{"Start":"04:39.920 ","End":"04:42.455","Text":"They are involuntary, as we said,"},{"Start":"04:42.455 ","End":"04:45.065","Text":"there\u0027s only 1 nucleus per cell in them,"},{"Start":"04:45.065 ","End":"04:48.890","Text":"and they are tapered if we look at one of these cells,"},{"Start":"04:48.890 ","End":"04:51.455","Text":"we can see that they\u0027re tapered at either end."},{"Start":"04:51.455 ","End":"04:53.270","Text":"In a moment we\u0027ll look,"},{"Start":"04:53.270 ","End":"04:54.710","Text":"or in another video, possibly,"},{"Start":"04:54.710 ","End":"05:00.110","Text":"we\u0027ll look at the skeletal muscles and we see that they form these big,"},{"Start":"05:00.110 ","End":"05:04.100","Text":"huge fibers and their shape is completely differently."},{"Start":"05:04.100 ","End":"05:08.870","Text":"Lastly, we\u0027ll look at another muscle, cardiac muscle."},{"Start":"05:08.870 ","End":"05:15.215","Text":"That\u0027s the muscle which is found in the heart and you can see it looks different as well."},{"Start":"05:15.215 ","End":"05:18.420","Text":"It does have the striations."},{"Start":"05:19.000 ","End":"05:21.940","Text":"Of course, it\u0027s involuntarily controlled,"},{"Start":"05:21.940 ","End":"05:24.050","Text":"we don\u0027t want to be able to stop our hearts."},{"Start":"05:24.050 ","End":"05:27.015","Text":"Interestingly, there\u0027s only 1 nucleus per cell."},{"Start":"05:27.015 ","End":"05:30.665","Text":"These cells are not tapered like the smooth muscle."},{"Start":"05:30.665 ","End":"05:32.660","Text":"Instead, they\u0027re branched."},{"Start":"05:32.660 ","End":"05:36.575","Text":"That causes the heart to be a tissue"},{"Start":"05:36.575 ","End":"05:40.980","Text":"which holds together very nicely because of this branching."},{"Start":"05:40.980 ","End":"05:45.350","Text":"It\u0027s distinguished by the presence of these intercalated discs."},{"Start":"05:45.350 ","End":"05:48.440","Text":"There are these discs that are found inside"},{"Start":"05:48.440 ","End":"05:53.190","Text":"the muscle tissue that helps us see it under a microscope."}],"ID":30261},{"Watched":false,"Name":"Myofibril Structure","Duration":"6m 50s","ChapterTopicVideoID":28731,"CourseChapterTopicPlaylistID":286922,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.720","Text":"We\u0027ve been discussing different types of muscles,"},{"Start":"00:03.720 ","End":"00:09.240","Text":"and now let\u0027s look in more detail at skeletal muscle."},{"Start":"00:09.240 ","End":"00:15.870","Text":"Skeletal muscle is set up in such a way that it makes these long fibers,"},{"Start":"00:15.870 ","End":"00:18.150","Text":"and that\u0027s what we\u0027re going to discuss here."},{"Start":"00:18.150 ","End":"00:23.265","Text":"Each skeletal muscle fiber is 1 cell, believe it or not."},{"Start":"00:23.265 ","End":"00:25.650","Text":"These cells can be very large."},{"Start":"00:25.650 ","End":"00:32.189","Text":"They can be even 100 microns in diameter and have lengths of 30 centimeters."},{"Start":"00:32.189 ","End":"00:34.605","Text":"The only other kind of cells that we know of that are"},{"Start":"00:34.605 ","End":"00:38.160","Text":"this long are some of the nerve cells."},{"Start":"00:38.160 ","End":"00:41.540","Text":"These light nerves can be very long,"},{"Start":"00:41.540 ","End":"00:47.185","Text":"but they have a very particular structure, these muscle fibers."},{"Start":"00:47.185 ","End":"00:50.720","Text":"For 1, they have a sarcolemma."},{"Start":"00:50.720 ","End":"00:56.165","Text":"It\u0027s a membrane which goes around the entire muscle fiber,"},{"Start":"00:56.165 ","End":"00:59.704","Text":"and that is the site of the action potential"},{"Start":"00:59.704 ","End":"01:03.530","Text":"conduction which triggers muscle contraction."},{"Start":"01:03.530 ","End":"01:05.810","Text":"There is, like in nerve cells,"},{"Start":"01:05.810 ","End":"01:08.975","Text":"There\u0027s an action potential so that there is"},{"Start":"01:08.975 ","End":"01:14.945","Text":"a contraction of the entire muscle at the same time."},{"Start":"01:14.945 ","End":"01:21.215","Text":"That\u0027s going to be very important for it to work properly."},{"Start":"01:21.215 ","End":"01:25.550","Text":"Next, we see that it\u0027s composed of myofibrils."},{"Start":"01:25.550 ","End":"01:29.030","Text":"Myofibrils, these little fibers that are in the inside,"},{"Start":"01:29.030 ","End":"01:31.130","Text":"they are long cylindrical structures,"},{"Start":"01:31.130 ","End":"01:34.745","Text":"they can be about 1.2 microns in diameter."},{"Start":"01:34.745 ","End":"01:39.665","Text":"They\u0027re parallel, they lie parallel within the muscle fiber."},{"Start":"01:39.665 ","End":"01:47.555","Text":"There are hundreds to even thousands that can be found inside 1 muscle fiber."},{"Start":"01:47.555 ","End":"01:55.570","Text":"They attach to the sarcolemma on the outside at their ends as well,"},{"Start":"01:55.570 ","End":"02:00.875","Text":"and as the myofibrils shorten when the muscle contracts,"},{"Start":"02:00.875 ","End":"02:04.580","Text":"then the entire cell contracts."},{"Start":"02:04.580 ","End":"02:08.375","Text":"The whole business here is going to contract."},{"Start":"02:08.375 ","End":"02:16.120","Text":"We\u0027re going to see how that happens in the continuation of this video."},{"Start":"02:16.120 ","End":"02:23.644","Text":"Remember we talked about striations that we can see in the skeletal muscles."},{"Start":"02:23.644 ","End":"02:26.495","Text":"The myofibril, in fact,"},{"Start":"02:26.495 ","End":"02:29.690","Text":"is composed of alternating bands that are"},{"Start":"02:29.690 ","End":"02:33.140","Text":"visible in a microscope and they\u0027re given titles."},{"Start":"02:33.140 ","End":"02:36.000","Text":"There are I-bands that are light color,"},{"Start":"02:36.000 ","End":"02:38.520","Text":"A-bands that are dark in color."},{"Start":"02:38.520 ","End":"02:44.000","Text":"Then each I-band that we see"},{"Start":"02:44.000 ","End":"02:53.043","Text":"these lighter color ones has a dense Z-line or Z-line that runs through the middle of it."},{"Start":"02:53.043 ","End":"02:56.420","Text":"It\u0027s called the Z-line because it goes back and forth and back and forth,"},{"Start":"02:56.420 ","End":"02:57.890","Text":"as you can see here,"},{"Start":"02:57.890 ","End":"02:59.945","Text":"that runs vertically through the middle."},{"Start":"02:59.945 ","End":"03:05.359","Text":"We\u0027re going to identify in a bit of what the function is of each of these structures."},{"Start":"03:05.359 ","End":"03:13.490","Text":"The Z-lines are going to mark the border of something we\u0027re going to call the sarcomere."},{"Start":"03:13.490 ","End":"03:18.125","Text":"The sarcomere is the functional unit of the skeletal muscle."},{"Start":"03:18.125 ","End":"03:19.670","Text":"As I mentioned before,"},{"Start":"03:19.670 ","End":"03:23.360","Text":"that myosin and actin are going to slide past 1 another,"},{"Start":"03:23.360 ","End":"03:28.660","Text":"that\u0027s what we\u0027ll see happens within the sarcomere."},{"Start":"03:28.660 ","End":"03:35.870","Text":"Each sarcomere is the space between the consecutive Z-lines or Z-lines as we said before."},{"Start":"03:35.870 ","End":"03:40.410","Text":"Each contains an entire A-band, of course,"},{"Start":"03:40.410 ","End":"03:45.595","Text":"so here\u0027s an A-band and 2/2 of the I-bands,"},{"Start":"03:45.595 ","End":"03:50.435","Text":"1/2 over here and 1/2 over here on each side."},{"Start":"03:50.435 ","End":"03:55.370","Text":"The myofibril, the entire thing is composed of many of"},{"Start":"03:55.370 ","End":"04:00.487","Text":"these sarcomeres that are 1 after the other that run along its length."},{"Start":"04:00.487 ","End":"04:04.670","Text":"As each of the sarcomeres individually contract,"},{"Start":"04:04.670 ","End":"04:08.925","Text":"the myofibrils in the muscle cells will shorten."},{"Start":"04:08.925 ","End":"04:14.959","Text":"The myofibrils have within them the actin and the myosin."},{"Start":"04:14.959 ","End":"04:18.140","Text":"Let\u0027s first address ourselves to myosin."},{"Start":"04:18.140 ","End":"04:24.980","Text":"These are what are called thick filaments that we see as the thick filaments in"},{"Start":"04:24.980 ","End":"04:32.795","Text":"our pictures in the micrographs and they occur only in the A-band,"},{"Start":"04:32.795 ","End":"04:34.100","Text":"right here\u0027s the A-band,"},{"Start":"04:34.100 ","End":"04:36.920","Text":"here\u0027s another A-band, of the myofibril."},{"Start":"04:36.920 ","End":"04:38.645","Text":"Then we have actin."},{"Start":"04:38.645 ","End":"04:46.130","Text":"Actin are the thin filaments that we see as opposed to the thick filaments of myosin,"},{"Start":"04:46.130 ","End":"04:54.010","Text":"they attach to another protein called Alpha-actinin the Z-line."},{"Start":"04:54.010 ","End":"04:57.875","Text":"We\u0027re going to have the actin attaching to something in the Z-line,"},{"Start":"04:57.875 ","End":"05:04.244","Text":"and this occurs across the entire length of the I-band,"},{"Start":"05:04.244 ","End":"05:10.005","Text":"and partway into the A-band; this attachment."},{"Start":"05:10.005 ","End":"05:14.705","Text":"The region at which both filaments overlap has a dense appearance,"},{"Start":"05:14.705 ","End":"05:20.235","Text":"so we have this area here where they overlap,"},{"Start":"05:20.235 ","End":"05:25.810","Text":"and this overlapping is very dense because it\u0027s both the thick and thin filaments there,"},{"Start":"05:25.810 ","End":"05:28.700","Text":"and there\u0027s very little space between these filaments,"},{"Start":"05:28.700 ","End":"05:31.015","Text":"and we\u0027ll understand why soon."},{"Start":"05:31.015 ","End":"05:35.150","Text":"Thin filaments do not extend all the way into the A-bands."},{"Start":"05:35.150 ","End":"05:37.640","Text":"They don\u0027t extend all the way,"},{"Start":"05:37.640 ","End":"05:39.830","Text":"as you can see in this picture,"},{"Start":"05:39.830 ","End":"05:44.255","Text":"leaving the central region of the a band that contains only the thick filaments."},{"Start":"05:44.255 ","End":"05:47.900","Text":"That\u0027s going to allow us to slide them 1 past the"},{"Start":"05:47.900 ","End":"05:52.010","Text":"other and fill the space when the muscle contracts."},{"Start":"05:52.010 ","End":"05:53.915","Text":"Now addition to this,"},{"Start":"05:53.915 ","End":"05:55.535","Text":"if we\u0027re looking at the microscope,"},{"Start":"05:55.535 ","End":"06:01.430","Text":"then we see an area that we call the H-zone within the A-band,"},{"Start":"06:01.430 ","End":"06:05.395","Text":"and we can identify another kind of line called the"},{"Start":"06:05.395 ","End":"06:09.635","Text":"M-line is a vertical line within this H-zone,"},{"Start":"06:09.635 ","End":"06:13.070","Text":"that\u0027s where the accessory proteins are going to hold"},{"Start":"06:13.070 ","End":"06:16.995","Text":"the thick filaments or myosin together."},{"Start":"06:16.995 ","End":"06:21.110","Text":"Both the Z-line and the M-line hold myofilaments in place to maintain"},{"Start":"06:21.110 ","End":"06:24.950","Text":"the structural arrangement and the integrity of"},{"Start":"06:24.950 ","End":"06:29.570","Text":"the muscle fiber and the layering of the myofibril."},{"Start":"06:29.570 ","End":"06:36.500","Text":"The myofibrils are connected to each other by another protein called desmin,"},{"Start":"06:36.500 ","End":"06:40.515","Text":"or sometimes desmin filaments that attach to this Z-line."},{"Start":"06:40.515 ","End":"06:43.940","Text":"We have to have structural integrity, of course,"},{"Start":"06:43.940 ","End":"06:47.960","Text":"across the myofibril because as it contracts,"},{"Start":"06:47.960 ","End":"06:50.850","Text":"we don\u0027t want it to tear."}],"ID":30262},{"Watched":false,"Name":"Actin and Myosin During Muscle Contraction","Duration":"5m 2s","ChapterTopicVideoID":28728,"CourseChapterTopicPlaylistID":286922,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:01.070 ","End":"00:04.860","Text":"We\u0027re going to continue our discussion now of"},{"Start":"00:04.860 ","End":"00:09.570","Text":"Muscle Contraction by looking more in depth at what\u0027s"},{"Start":"00:09.570 ","End":"00:13.695","Text":"going on inside the skeletal muscle myofibrils"},{"Start":"00:13.695 ","End":"00:17.430","Text":"and turn our attention to the thick filaments."},{"Start":"00:17.430 ","End":"00:25.410","Text":"Remember the thick filaments are composed of myosin protein that we described before."},{"Start":"00:25.410 ","End":"00:31.760","Text":"If we look at the structure of the myosin molecules,"},{"Start":"00:31.760 ","End":"00:33.710","Text":"we\u0027ll see that there are 2 parts."},{"Start":"00:33.710 ","End":"00:36.740","Text":"There are the parts that are longer,"},{"Start":"00:36.740 ","End":"00:42.020","Text":"elongated a tail, and each of them also has a head."},{"Start":"00:42.020 ","End":"00:46.400","Text":"The tail of the myosin molecule connects with other myosin molecules,"},{"Start":"00:46.400 ","End":"00:47.645","Text":"as we can see here,"},{"Start":"00:47.645 ","End":"00:54.275","Text":"that form the central region of these thick filaments near the M-line."},{"Start":"00:54.275 ","End":"00:58.610","Text":"The heads of the myosin over here,"},{"Start":"00:58.610 ","End":"01:02.540","Text":"a line on either side of the thick filaments where the thin filaments overlap"},{"Start":"01:02.540 ","End":"01:07.025","Text":"and they are going to be connecting with the actin."},{"Start":"01:07.025 ","End":"01:12.965","Text":"The business end really is going to be the head of the myosin molecule."},{"Start":"01:12.965 ","End":"01:16.310","Text":"Notice the length of this can be quite long,"},{"Start":"01:16.310 ","End":"01:18.410","Text":"100 nanometers or so."},{"Start":"01:18.410 ","End":"01:21.920","Text":"The thin filaments are made of actin,"},{"Start":"01:21.920 ","End":"01:27.980","Text":"as we described before primarily and then there are some control molecules,"},{"Start":"01:27.980 ","End":"01:30.620","Text":"tropomyosin, and troponin."},{"Start":"01:30.620 ","End":"01:32.800","Text":"Tropomyosin and troponin,"},{"Start":"01:32.800 ","End":"01:37.550","Text":"you can see them shown here where the actin is in the center here"},{"Start":"01:37.550 ","End":"01:42.735","Text":"in this fibrous kind of polymer of actin."},{"Start":"01:42.735 ","End":"01:49.655","Text":"Actin has particular sites on it for the myosin head attachment."},{"Start":"01:49.655 ","End":"01:53.850","Text":"The strands of tropomyosin function to block"},{"Start":"01:53.850 ","End":"01:56.810","Text":"these binding sites of the actin and prevent"},{"Start":"01:56.810 ","End":"02:00.440","Text":"actin-myosin interactions when the muscles are at rest."},{"Start":"02:00.440 ","End":"02:03.860","Text":"It\u0027s going to be the actin-myosin interactions,"},{"Start":"02:03.860 ","End":"02:07.660","Text":"as we\u0027ll see, they\u0027re going to cause muscle contraction."},{"Start":"02:07.660 ","End":"02:12.355","Text":"Troponin has 311 globular subunits,"},{"Start":"02:12.355 ","End":"02:16.505","Text":"an actin-myosin ATPase inhibitory subunits."},{"Start":"02:16.505 ","End":"02:19.400","Text":"We\u0027re going to see that ATP is going to be very important,"},{"Start":"02:19.400 ","End":"02:21.380","Text":"of course, for the contraction."},{"Start":"02:21.380 ","End":"02:27.163","Text":"There\u0027s a T sub unit that\u0027s a tropomyosin binding subunits,"},{"Start":"02:27.163 ","End":"02:30.620","Text":"and there\u0027s a C subunit which is going to bind calcium."},{"Start":"02:30.620 ","End":"02:36.750","Text":"Calcium ions are very important for this entire process."},{"Start":"02:37.030 ","End":"02:39.350","Text":"As I\u0027ve mentioned before,"},{"Start":"02:39.350 ","End":"02:41.975","Text":"but now we can see this in a figure,"},{"Start":"02:41.975 ","End":"02:45.035","Text":"there\u0027s sliding of the filaments,"},{"Start":"02:45.035 ","End":"02:47.000","Text":"of the thick and thin filaments,"},{"Start":"02:47.000 ","End":"02:50.450","Text":"the myosin, and"},{"Start":"02:50.450 ","End":"02:55.540","Text":"the actin filaments past each other so that when the muscle is contracted,"},{"Start":"02:55.540 ","End":"03:03.650","Text":"they fill this area of the sarcomere both in the same space,"},{"Start":"03:03.650 ","End":"03:10.265","Text":"whereas when the muscle is relaxed then they move apart from each other,"},{"Start":"03:10.265 ","End":"03:14.330","Text":"somewhat in the muscle can become relaxed."},{"Start":"03:14.330 ","End":"03:15.920","Text":"When the muscles contract,"},{"Start":"03:15.920 ","End":"03:20.000","Text":"the thick filaments and the thin filaments slide by one another"},{"Start":"03:20.000 ","End":"03:24.080","Text":"causing the sarcomere to shorten and the filaments themselves,"},{"Start":"03:24.080 ","End":"03:26.740","Text":"however, remain the same length,"},{"Start":"03:26.740 ","End":"03:31.835","Text":"it\u0027s just the sliding past one another that causes the muscle to contract."},{"Start":"03:31.835 ","End":"03:34.775","Text":"The contracting sarcomere, of course,"},{"Start":"03:34.775 ","End":"03:37.855","Text":"generates tension in the muscle."},{"Start":"03:37.855 ","End":"03:43.535","Text":"Now let\u0027s look at more detail at this and we\u0027ll look at sarcomere contraction."},{"Start":"03:43.535 ","End":"03:49.220","Text":"When muscles contract, the distance between the Z-lines, of course,"},{"Start":"03:49.220 ","End":"03:52.714","Text":"is going to become less because we have this sliding"},{"Start":"03:52.714 ","End":"03:56.600","Text":"of the actin and the myosin with respect to each other."},{"Start":"03:56.600 ","End":"04:03.890","Text":"The H-zone contains only thick filaments and it\u0027s also shortened a bit"},{"Start":"04:03.890 ","End":"04:07.340","Text":"because of where the edges of it are defined"},{"Start":"04:07.340 ","End":"04:12.185","Text":"because the H-zone does not contain the actin."},{"Start":"04:12.185 ","End":"04:19.465","Text":"The I-band contains only thin filaments and it shortens for the same reason."},{"Start":"04:19.465 ","End":"04:27.635","Text":"The A-band, of course remains the same length because that\u0027s the center here,"},{"Start":"04:27.635 ","End":"04:32.990","Text":"where we don\u0027t have the actin that overlaps,"},{"Start":"04:32.990 ","End":"04:38.840","Text":"so it stays the same and eventually disappears when everything is very contracted."},{"Start":"04:38.840 ","End":"04:45.440","Text":"The actin filaments are pulled toward the center of the sarcomere"},{"Start":"04:45.440 ","End":"04:52.335","Text":"until the Z-line approaches this H-zone."},{"Start":"04:52.335 ","End":"04:56.930","Text":"This overlap zone of actin and myosin filaments increases, of course,"},{"Start":"04:56.930 ","End":"04:59.720","Text":"as the actin filaments move inward,"},{"Start":"04:59.720 ","End":"05:02.490","Text":"when we look at it in the microscope."}],"ID":30263},{"Watched":false,"Name":"Mechanism of Contraction","Duration":"4m 39s","ChapterTopicVideoID":28727,"CourseChapterTopicPlaylistID":286922,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.500","Text":"Now, we\u0027re going to continue our discussion of muscle contraction by"},{"Start":"00:04.500 ","End":"00:09.060","Text":"looking at the mechanism of how the myosin and"},{"Start":"00:09.060 ","End":"00:12.720","Text":"the actin are interacting with each other and how"},{"Start":"00:12.720 ","End":"00:17.850","Text":"ATP plays a central role in this entire process."},{"Start":"00:17.850 ","End":"00:20.595","Text":"ATP and muscle contraction."},{"Start":"00:20.595 ","End":"00:27.809","Text":"Muscle contraction occurs as myosin heads bind actin and pull the actin inwards,"},{"Start":"00:27.809 ","End":"00:29.475","Text":"as we discussed before."},{"Start":"00:29.475 ","End":"00:33.450","Text":"This is going to require ATP."},{"Start":"00:33.450 ","End":"00:39.540","Text":"ATP binding causes myosin to release the actin, as it turns out,"},{"Start":"00:39.540 ","End":"00:44.610","Text":"allowing the actin-myosin to detach from each other,"},{"Start":"00:44.610 ","End":"00:49.235","Text":"and of course, that is going to make the muscle relax."},{"Start":"00:49.235 ","End":"00:53.360","Text":"The energy that\u0027s released during ATP hydrolysis"},{"Start":"00:53.360 ","End":"00:58.625","Text":"changes the angle of the myosin head into a cocked position."},{"Start":"00:58.625 ","End":"01:02.375","Text":"ATP actually is expanded not"},{"Start":"01:02.375 ","End":"01:06.680","Text":"when the muscle is contracting it\u0027s a little bit counter-intuitive,"},{"Start":"01:06.680 ","End":"01:09.980","Text":"but this happens when the muscle is relaxing."},{"Start":"01:09.980 ","End":"01:14.165","Text":"ATP is split into ADP and pyrophosphate,"},{"Start":"01:14.165 ","End":"01:16.130","Text":"but in the course of doing that,"},{"Start":"01:16.130 ","End":"01:20.300","Text":"the myosin head is energized and is cocked."},{"Start":"01:20.300 ","End":"01:26.900","Text":"The head changes its position relative to"},{"Start":"01:26.900 ","End":"01:33.890","Text":"the tail of the myosin and that is going to be now set to cause a contraction."},{"Start":"01:33.890 ","End":"01:38.075","Text":"Now if the actin binding sites are uncovered,"},{"Start":"01:38.075 ","End":"01:39.800","Text":"and that\u0027s going to be controlled,"},{"Start":"01:39.800 ","End":"01:42.610","Text":"of course, by the troponin,"},{"Start":"01:42.610 ","End":"01:46.160","Text":"then a cross-bridge will form,"},{"Start":"01:46.160 ","End":"01:49.730","Text":"as you can see over here and the myosin head spans"},{"Start":"01:49.730 ","End":"01:54.990","Text":"the distance between the actin and myosin molecules."},{"Start":"01:55.120 ","End":"01:58.850","Text":"Pyrophosphate is released and that allows"},{"Start":"01:58.850 ","End":"02:03.785","Text":"the myosin to expend the stored energy as a conformational change."},{"Start":"02:03.785 ","End":"02:14.060","Text":"Now, there is a conformational change again so that the head was cocked and"},{"Start":"02:14.060 ","End":"02:18.665","Text":"then it changes its conformation in something that we might call a power stroke"},{"Start":"02:18.665 ","End":"02:25.175","Text":"as the actin filament moves and as the muscle contracts."},{"Start":"02:25.175 ","End":"02:26.630","Text":"In the power stroke,"},{"Start":"02:26.630 ","End":"02:31.940","Text":"the myosin head moves towards the M-line pulling actin along with it and this"},{"Start":"02:31.940 ","End":"02:38.255","Text":"happens causing approximately a 10 nanometer move toward the M-line."},{"Start":"02:38.255 ","End":"02:40.100","Text":"As the actin is pulled toward the M-line,"},{"Start":"02:40.100 ","End":"02:41.570","Text":"the sarcomere shortens, of course,"},{"Start":"02:41.570 ","End":"02:43.010","Text":"and the muscle contracts."},{"Start":"02:43.010 ","End":"02:45.230","Text":"At the end of this power stroke,"},{"Start":"02:45.230 ","End":"02:48.020","Text":"the myosin head is in a low-energy position,"},{"Start":"02:48.020 ","End":"02:51.570","Text":"surely because it\u0027s expended the energy."},{"Start":"02:51.570 ","End":"02:53.135","Text":"After the power stroke,"},{"Start":"02:53.135 ","End":"02:59.150","Text":"ADP is released, as was the pyrophosphate before."},{"Start":"02:59.150 ","End":"03:02.300","Text":"The cross-bridge notice is still in place and"},{"Start":"03:02.300 ","End":"03:05.270","Text":"the actin and myosin are bound together and that\u0027s"},{"Start":"03:05.270 ","End":"03:11.945","Text":"the case until new ATP is going to be attached to the myosin,"},{"Start":"03:11.945 ","End":"03:17.260","Text":"releasing it as the muscle is relaxed."},{"Start":"03:17.260 ","End":"03:19.720","Text":"Now, let\u0027s look at the regulatory proteins."},{"Start":"03:19.720 ","End":"03:21.835","Text":"We\u0027ve talked about troponin."},{"Start":"03:21.835 ","End":"03:31.300","Text":"At the resting state actin and myosin are kept apart by tropomyosin that we can see here,"},{"Start":"03:31.300 ","End":"03:35.230","Text":"which prevents this cross-bridge formation without nervous input,"},{"Start":"03:35.230 ","End":"03:40.010","Text":"troponin binds to the tropomyosin and"},{"Start":"03:40.010 ","End":"03:45.300","Text":"helps position it on the actin filament and it also binds calcium ions."},{"Start":"03:45.300 ","End":"03:48.700","Text":"When there\u0027s a nerve motor inputs that is,"},{"Start":"03:48.700 ","End":"03:55.750","Text":"when the nerve has an action potential causing the muscle to contract,"},{"Start":"03:55.750 ","End":"03:58.360","Text":"then there is release of calcium ions from"},{"Start":"03:58.360 ","End":"04:05.330","Text":"the sarcoplasmic reticulum and the calcium ions bind now to troponin,"},{"Start":"04:05.330 ","End":"04:12.890","Text":"shifting the tropomyosin-troponin complex and then unblocking that myosin binding site."},{"Start":"04:12.890 ","End":"04:19.110","Text":"Remember those myosin binding sites were required in order to get contraction."},{"Start":"04:19.110 ","End":"04:21.380","Text":"Once the tropomyosin is removed,"},{"Start":"04:21.380 ","End":"04:27.605","Text":"then the cross-bridge can form between the actin and myosin and we get the contraction."},{"Start":"04:27.605 ","End":"04:31.550","Text":"The cross-bridge cycling continues until calcium,"},{"Start":"04:31.550 ","End":"04:39.260","Text":"ATP are no longer available and then troponin is going to cover the binding sites again."}],"ID":30264},{"Watched":false,"Name":"Nervous Stimulation of Muscle","Duration":"8m 3s","ChapterTopicVideoID":28730,"CourseChapterTopicPlaylistID":286922,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.160","Text":"In the previous videos,"},{"Start":"00:02.160 ","End":"00:05.970","Text":"we\u0027ve discussed the structure of muscles and what"},{"Start":"00:05.970 ","End":"00:10.335","Text":"the mechanism is when the muscle fiber contracts."},{"Start":"00:10.335 ","End":"00:15.240","Text":"Now, we\u0027re going to discuss its activation and the control of how"},{"Start":"00:15.240 ","End":"00:21.015","Text":"strongly the muscle works and how that is controlled."},{"Start":"00:21.015 ","End":"00:24.870","Text":"There\u0027s this excitation contraction coupling,"},{"Start":"00:24.870 ","End":"00:31.110","Text":"the excitation of the nerve and the coupling of the nerve with the fiber."},{"Start":"00:31.110 ","End":"00:34.020","Text":"This defines a transduction,"},{"Start":"00:34.020 ","End":"00:39.330","Text":"a link between the action potential is generated in the sarcolemma by"},{"Start":"00:39.330 ","End":"00:46.325","Text":"the nerve that\u0027s interacting with it and the start of muscle fiber contraction."},{"Start":"00:46.325 ","End":"00:50.420","Text":"Each muscle fiber is controlled by a motor neuron."},{"Start":"00:50.420 ","End":"00:53.585","Text":"Each of them is controlled by a single motor neuron,"},{"Start":"00:53.585 ","End":"00:55.520","Text":"and this conducts signals from the brain,"},{"Start":"00:55.520 ","End":"00:57.770","Text":"of course, the spinal cord to the muscle."},{"Start":"00:57.770 ","End":"01:00.290","Text":"The electrical signals, as usual,"},{"Start":"01:00.290 ","End":"01:08.915","Text":"travel along the neuron\u0027s axon and then it can branch to the individual muscle fibers,"},{"Start":"01:08.915 ","End":"01:15.409","Text":"interact with the muscle fiber at a neuromuscular junction."},{"Start":"01:15.409 ","End":"01:18.485","Text":"Now, how does that work?"},{"Start":"01:18.485 ","End":"01:28.159","Text":"Of course, there\u0027s depolarization of this muscle cell which starts"},{"Start":"01:28.159 ","End":"01:32.870","Text":"by the action potential coming through the axon"},{"Start":"01:32.870 ","End":"01:38.096","Text":"and then releasing acetylcholine by these motor neurons,"},{"Start":"01:38.096 ","End":"01:42.447","Text":"and they bind receptors that are on the sarcolemma,"},{"Start":"01:42.447 ","End":"01:47.180","Text":"depolarizing the sarcolemma, as is usual."},{"Start":"01:47.180 ","End":"01:51.230","Text":"Now, the next thing that happens is that there\u0027s an action potential which"},{"Start":"01:51.230 ","End":"01:55.100","Text":"actually moves along the sarcolemma down"},{"Start":"01:55.100 ","End":"02:04.640","Text":"through some tubes called T-tubules that are in the membrane of these muscle cells"},{"Start":"02:04.640 ","End":"02:09.545","Text":"and this action potential in the T-tubule activates"},{"Start":"02:09.545 ","End":"02:15.845","Text":"voltage sensitive receptors in these SR tubules."},{"Start":"02:15.845 ","End":"02:22.535","Text":"Yes, that release calcium into"},{"Start":"02:22.535 ","End":"02:29.885","Text":"the cytosol from these terminal cisternae of the sarcoplasmic reticulum."},{"Start":"02:29.885 ","End":"02:31.880","Text":"We have the sarcoplasmic reticulum,"},{"Start":"02:31.880 ","End":"02:37.580","Text":"the structure that is releasing calcium into the cytosol as"},{"Start":"02:37.580 ","End":"02:41.180","Text":"the result of the depolarization that is"},{"Start":"02:41.180 ","End":"02:45.620","Text":"activated by the acetylcholine receptor of the nerve."},{"Start":"02:45.620 ","End":"02:50.360","Text":"Next, of course, this calcium binds to troponin,"},{"Start":"02:50.360 ","End":"02:51.650","Text":"as we\u0027ve seen before,"},{"Start":"02:51.650 ","End":"02:53.270","Text":"changes its shape,"},{"Start":"02:53.270 ","End":"02:58.325","Text":"removing the blocking action of tropomyosin and"},{"Start":"02:58.325 ","End":"03:03.685","Text":"that results in the active sites of actin being exposed."},{"Start":"03:03.685 ","End":"03:05.415","Text":"Now, you remember that,"},{"Start":"03:05.415 ","End":"03:09.050","Text":"that means that then the myosin can interact."},{"Start":"03:09.050 ","End":"03:10.220","Text":"The head of the myosin,"},{"Start":"03:10.220 ","End":"03:14.525","Text":"that\u0027s cocked can bind with that actin"},{"Start":"03:14.525 ","End":"03:20.120","Text":"and the myosin heads then alternately attached to the actin and detach,"},{"Start":"03:20.120 ","End":"03:24.020","Text":"pulling the actin filaments towards the center of the sarcomere."},{"Start":"03:24.020 ","End":"03:26.960","Text":"That means that there is contraction."},{"Start":"03:26.960 ","End":"03:33.190","Text":"Now, release of energy by ATP or hydrolysis is what is powering the system."},{"Start":"03:33.190 ","End":"03:34.330","Text":"We have contraction,"},{"Start":"03:34.330 ","End":"03:38.710","Text":"the myosin heads pull the actin filaments toward the center of the sarcomere."},{"Start":"03:38.710 ","End":"03:43.325","Text":"Next, we\u0027re going to want to reverse this to relax it."},{"Start":"03:43.325 ","End":"03:51.640","Text":"The calcium then which is removed by active transport from the cytosol back into"},{"Start":"03:51.640 ","End":"04:01.075","Text":"the SR tubules ends this contraction and we have a relaxation of the muscle,"},{"Start":"04:01.075 ","End":"04:05.545","Text":"the tropomyosin blockage is restored as we saw before"},{"Start":"04:05.545 ","End":"04:12.875","Text":"and that muscle fiber relaxes."},{"Start":"04:12.875 ","End":"04:14.840","Text":"Now, let\u0027s see how this is controlled."},{"Start":"04:14.840 ","End":"04:17.795","Text":"How is this tension controlled?"},{"Start":"04:17.795 ","End":"04:22.355","Text":"The force or the tension is controlled by"},{"Start":"04:22.355 ","End":"04:27.290","Text":"how many of these fibers actually are being used."},{"Start":"04:27.290 ","End":"04:32.150","Text":"In an individual muscle fiber,"},{"Start":"04:32.150 ","End":"04:36.230","Text":"the amount of tension produced on the cross-sectional area of actin and"},{"Start":"04:36.230 ","End":"04:40.430","Text":"myosin fibers and then the frequency of neural stimulation,"},{"Start":"04:40.430 ","End":"04:43.970","Text":"which is going to mean how many of"},{"Start":"04:43.970 ","End":"04:49.310","Text":"these sarcomeres are going to be activated if more cross bridges are formed,"},{"Start":"04:49.310 ","End":"04:51.320","Text":"of course, there is more attention."},{"Start":"04:51.320 ","End":"04:55.055","Text":"Now, the maximal tension occurs when"},{"Start":"04:55.055 ","End":"04:59.150","Text":"the thick and thin filaments overlap to the greatest degree of course."},{"Start":"04:59.150 ","End":"05:01.400","Text":"If they don\u0027t overlap,"},{"Start":"05:01.400 ","End":"05:04.280","Text":"then few less tension is produced."},{"Start":"05:04.280 ","End":"05:06.520","Text":"As a sarcomeres are shortened,"},{"Start":"05:06.520 ","End":"05:10.565","Text":"the overlap zone is reduced as the thin filaments reach the H-zone,"},{"Start":"05:10.565 ","End":"05:13.835","Text":"which is composed of course of these myosin tails."},{"Start":"05:13.835 ","End":"05:22.160","Text":"Because myosin heads form cross-bridges actin will not now bind to myosin in that zone,"},{"Start":"05:22.160 ","End":"05:27.500","Text":"and that reduces the tension after the contraction has begun to occur."},{"Start":"05:27.500 ","End":"05:30.620","Text":"Now, the degree of the filament overlapping,"},{"Start":"05:30.620 ","End":"05:38.075","Text":"so the tension is going to be a function of the degree of filaments that are overlapping."},{"Start":"05:38.075 ","End":"05:40.130","Text":"If the sarcomere is shortened,"},{"Start":"05:40.130 ","End":"05:43.220","Text":"more thin filaments begin to overlap with each other,"},{"Start":"05:43.220 ","End":"05:50.105","Text":"reducing cross-bridge formation even further and producing even less tension."},{"Start":"05:50.105 ","End":"05:54.695","Text":"However, conversely, if the sarcomere is overstretched,"},{"Start":"05:54.695 ","End":"05:59.600","Text":"then the filaments don\u0027t overlap and there\u0027s no tension."},{"Start":"05:59.600 ","End":"06:04.385","Text":"If the muscle is stretched too much, it can contract."},{"Start":"06:04.385 ","End":"06:11.030","Text":"This is really rare because of all the accessory proteins that keep this from happening."},{"Start":"06:11.030 ","End":"06:19.310","Text":"Lastly, it turns out that the nerve stimulation can occur to only some of the fibers."},{"Start":"06:19.310 ","End":"06:21.890","Text":"In this case, say 5 fibers, 7 fibers,"},{"Start":"06:21.890 ","End":"06:25.100","Text":"12 fibers and that is going to determine"},{"Start":"06:25.100 ","End":"06:29.735","Text":"how much tension a particular muscle is going to have."},{"Start":"06:29.735 ","End":"06:33.680","Text":"In the biceps, let\u0027s say we are going to pick up a pencil,"},{"Start":"06:33.680 ","End":"06:35.165","Text":"or something that\u0027s very light,"},{"Start":"06:35.165 ","End":"06:36.980","Text":"then the motor complex,"},{"Start":"06:36.980 ","End":"06:40.655","Text":"the brain is only going to send a few signals to the biceps,"},{"Start":"06:40.655 ","End":"06:44.930","Text":"and only a few of the myofibrils will contract."},{"Start":"06:44.930 ","End":"06:49.040","Text":"We don\u0027t have much of a strong response."},{"Start":"06:49.040 ","End":"06:56.145","Text":"In vertebrates each individual myofibril is fully stimulated."},{"Start":"06:56.145 ","End":"07:01.730","Text":"It\u0027s going to be the number of these myofibrils that are stimulated,"},{"Start":"07:01.730 ","End":"07:03.455","Text":"as you can see down here,"},{"Start":"07:03.455 ","End":"07:07.085","Text":"that is going to cause a differential tension."},{"Start":"07:07.085 ","End":"07:12.065","Text":"Of course, if we picking up a piano and we need a lot of tension"},{"Start":"07:12.065 ","End":"07:16.984","Text":"then the motor cortex will signal all of the neurons and the biceps,"},{"Start":"07:16.984 ","End":"07:20.845","Text":"and all of the myofibrils will participate."},{"Start":"07:20.845 ","End":"07:24.620","Text":"That will cause a maximum force on the muscle,"},{"Start":"07:24.620 ","End":"07:28.460","Text":"increasing the frequency of action potentials."},{"Start":"07:28.460 ","End":"07:32.930","Text":"How often the action potential actually comes across"},{"Start":"07:32.930 ","End":"07:37.490","Text":"to the neuromuscular junction does increase the force a bit more,"},{"Start":"07:37.490 ","End":"07:44.930","Text":"but the majority of it has to do with how many of these fibers are activated."},{"Start":"07:44.930 ","End":"07:50.615","Text":"This is if the frequency of the action potential increases,"},{"Start":"07:50.615 ","End":"07:56.355","Text":"then we\u0027re going to get more calcium flooding the tropomyosin,"},{"Start":"07:56.355 ","End":"07:57.920","Text":"but the amount that,"},{"Start":"07:57.920 ","End":"08:02.430","Text":"that contributes to the force is relatively small."}],"ID":30265}],"Thumbnail":null,"ID":286922},{"Name":"Exercises","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Exercise 1","Duration":"39s","ChapterTopicVideoID":28842,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.370","Text":"The forearm consists of which of the following bones?"},{"Start":"00:05.370 ","End":"00:08.580","Text":"Radius and ulna, radius and humerus."},{"Start":"00:08.580 ","End":"00:14.265","Text":"Ulna and humerus, humerus and carpus."},{"Start":"00:14.265 ","End":"00:20.295","Text":"Let\u0027s see, if we remember the names of the various bones,"},{"Start":"00:20.295 ","End":"00:28.890","Text":"then we\u0027ll know that it is the radius and ulna that are in the forearm."},{"Start":"00:28.890 ","End":"00:34.905","Text":"The forearm is the part which is in the forward part near the hand."},{"Start":"00:34.905 ","End":"00:39.130","Text":"The answer is radius and ulna."}],"ID":30329},{"Watched":false,"Name":"Exercise 2","Duration":"42s","ChapterTopicVideoID":28843,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:07.695","Text":"The pectoral girdle consists of which of the following?"},{"Start":"00:07.695 ","End":"00:10.880","Text":"We just have to remember the names of these various bones,"},{"Start":"00:10.880 ","End":"00:12.260","Text":"clavicle and sternum,"},{"Start":"00:12.260 ","End":"00:13.790","Text":"sternum and scapula,"},{"Start":"00:13.790 ","End":"00:18.705","Text":"clavicle and scapula or clavicle and coccyx?"},{"Start":"00:18.705 ","End":"00:21.510","Text":"Well, it\u0027s certainly going to be clavicle."},{"Start":"00:21.510 ","End":"00:26.340","Text":"Which is it? It\u0027s the clavicle and scapula."},{"Start":"00:26.340 ","End":"00:31.070","Text":"If you remember, the scapula is the shoulder bone that we have behind,"},{"Start":"00:31.070 ","End":"00:35.535","Text":"and the clavicle is the bone that is in our front"},{"Start":"00:35.535 ","End":"00:41.290","Text":"that connects our sternum in the front with our shoulder."}],"ID":30330},{"Watched":false,"Name":"Exercise 3","Duration":"41s","ChapterTopicVideoID":28844,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.614","Text":"All of the following are groups of vertebrae,"},{"Start":"00:03.614 ","End":"00:06.315","Text":"except which of these,"},{"Start":"00:06.315 ","End":"00:08.335","Text":"which is a curvature?"},{"Start":"00:08.335 ","End":"00:12.675","Text":"Thoracic, cervical, lumbar, or pelvic."},{"Start":"00:12.675 ","End":"00:14.235","Text":"What are we being asked here?"},{"Start":"00:14.235 ","End":"00:17.565","Text":"We\u0027re asked which of these is"},{"Start":"00:17.565 ","End":"00:25.605","Text":"not a group of vertebrae and the answer is,"},{"Start":"00:25.605 ","End":"00:32.230","Text":"of course, pelvic, which is not part of the vertebra."},{"Start":"00:33.140 ","End":"00:40.540","Text":"The pelvic area is not part of the vertebra."}],"ID":30331},{"Watched":false,"Name":"Exercise 4","Duration":"42s","ChapterTopicVideoID":28845,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.110","Text":"Which of these is a facial bone?"},{"Start":"00:04.110 ","End":"00:09.015","Text":"Frontal, occipital, lacrimal, or temporal?"},{"Start":"00:09.015 ","End":"00:10.800","Text":"Well, let\u0027s see."},{"Start":"00:10.800 ","End":"00:14.037","Text":"It\u0027s going to be lacrimal, if you remember."},{"Start":"00:14.037 ","End":"00:15.870","Text":"The lacrimal, yes, here\u0027s the lacrimal bone,"},{"Start":"00:15.870 ","End":"00:20.850","Text":"it\u0027s a facial bone."},{"Start":"00:20.850 ","End":"00:26.820","Text":"The lacrimal bone is the bone which is around our eye."},{"Start":"00:26.820 ","End":"00:29.010","Text":"It\u0027s a piece that\u0027s around our eye,"},{"Start":"00:29.010 ","End":"00:32.400","Text":"and so that\u0027s going to be a facial bone."},{"Start":"00:32.400 ","End":"00:34.080","Text":"The frontal, occipital,"},{"Start":"00:34.080 ","End":"00:41.560","Text":"and temporal bones are bones of the skull, not the face."}],"ID":30332},{"Watched":false,"Name":"Exercise 5","Duration":"1m 44s","ChapterTopicVideoID":28846,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.827","Text":"Which of the following is not a true statement comparing exoskeletons and endoskeletons?"},{"Start":"00:06.827 ","End":"00:09.180","Text":"Remember, exoskeletons are going to be"},{"Start":"00:09.180 ","End":"00:12.930","Text":"the skeletons that are on the outsides of organism,"},{"Start":"00:12.930 ","End":"00:14.010","Text":"let\u0027s say in insects,"},{"Start":"00:14.010 ","End":"00:16.440","Text":"for instance, or in shellfish."},{"Start":"00:16.440 ","End":"00:20.025","Text":"Endoskeletons are the skeletons we normally think about,"},{"Start":"00:20.025 ","End":"00:22.530","Text":"the ones that are inside our body,"},{"Start":"00:22.530 ","End":"00:25.035","Text":"the skeletons of the various bones we have."},{"Start":"00:25.035 ","End":"00:27.825","Text":"Which is not a true statement?"},{"Start":"00:27.825 ","End":"00:32.610","Text":"That endoskeletons can support larger organisms."},{"Start":"00:32.610 ","End":"00:35.615","Text":"Well, let\u0027s think about that for a moment."},{"Start":"00:35.615 ","End":"00:38.360","Text":"They certainly do support large organisms."},{"Start":"00:38.360 ","End":"00:41.390","Text":"The endoskeletons, the ones that are inside."},{"Start":"00:41.390 ","End":"00:45.020","Text":"Only endoskeletons can grow as an organism grows."},{"Start":"00:45.020 ","End":"00:46.400","Text":"Well, they both grow,"},{"Start":"00:46.400 ","End":"00:47.930","Text":"so that\u0027s not going to be right."},{"Start":"00:47.930 ","End":"00:53.726","Text":"Exoskeletons provide greater protection of the internal organs."},{"Start":"00:53.726 ","End":"00:59.740","Text":"The exoskeletons are going to be on the outside,"},{"Start":"00:59.740 ","End":"01:02.255","Text":"so they do protect them."},{"Start":"01:02.255 ","End":"01:06.990","Text":"However, there are endoskeletons that also provide protection,"},{"Start":"01:06.990 ","End":"01:08.910","Text":"let\u0027s say the rib cage for the sternum,"},{"Start":"01:08.910 ","End":"01:11.855","Text":"for instance. That\u0027s not right."},{"Start":"01:11.855 ","End":"01:15.385","Text":"What about exoskeletons provide less mechanical leverage?"},{"Start":"01:15.385 ","End":"01:18.785","Text":"Let\u0027s think for a moment about the leverage"},{"Start":"01:18.785 ","End":"01:22.865","Text":"that is produced by the exoskeleton of a joint,"},{"Start":"01:22.865 ","End":"01:24.410","Text":"let\u0027s say in this grasshopper,"},{"Start":"01:24.410 ","End":"01:29.790","Text":"or the claw of a lobster, for instance."},{"Start":"01:29.790 ","End":"01:32.755","Text":"That can provide plenty of mechanical leverage."},{"Start":"01:32.755 ","End":"01:38.705","Text":"It\u0027s not true that exoskeletons provide less mechanical leverage."},{"Start":"01:38.705 ","End":"01:41.360","Text":"We were asked what is not true,"},{"Start":"01:41.360 ","End":"01:44.610","Text":"so the correct answer here is D."}],"ID":30333},{"Watched":false,"Name":"Exercise 6","Duration":"1m 16s","ChapterTopicVideoID":28847,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.295","Text":"Here we\u0027ve got a question regarding the Haversian canal."},{"Start":"00:05.295 ","End":"00:11.595","Text":"We want to know is whether the canal is arranged as rods or plates,"},{"Start":"00:11.595 ","End":"00:13.335","Text":"whether contains the bones,"},{"Start":"00:13.335 ","End":"00:16.770","Text":"blood vessels and nerve fibers is responsible for"},{"Start":"00:16.770 ","End":"00:23.245","Text":"the lengthwise growth of long bones or it synthesizes and secretes matrix."},{"Start":"00:23.245 ","End":"00:27.585","Text":"Let\u0027s recall what the Haversian canal is."},{"Start":"00:27.585 ","End":"00:32.550","Text":"It is the canal in the center of bones."},{"Start":"00:32.550 ","End":"00:36.930","Text":"These Haversian canals are microscopic tubes or tunnels that"},{"Start":"00:36.930 ","End":"00:42.960","Text":"house what nerve fibers and some blood vessels."},{"Start":"00:42.960 ","End":"00:47.855","Text":"Let\u0027s go back to our question for a moment and we\u0027ll see"},{"Start":"00:47.855 ","End":"00:52.910","Text":"that the correct answer will be the one that contains the bones,"},{"Start":"00:52.910 ","End":"00:55.400","Text":"blood vessels, and nerve fibers."},{"Start":"00:55.400 ","End":"00:59.029","Text":"Clearly, they\u0027re not arranged as rods or plates."},{"Start":"00:59.029 ","End":"01:00.470","Text":"They\u0027re not responsible for"},{"Start":"01:00.470 ","End":"01:04.105","Text":"the lengthwise growth of long bones will come to that in a bit."},{"Start":"01:04.105 ","End":"01:07.970","Text":"It certainly does not synthesize and secrete matrix."},{"Start":"01:07.970 ","End":"01:12.815","Text":"The Haversian canal contains the bones, blood vessels."},{"Start":"01:12.815 ","End":"01:16.290","Text":"As we can see here."}],"ID":30334},{"Watched":false,"Name":"Exercise 7","Duration":"1m 59s","ChapterTopicVideoID":28848,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.320 ","End":"00:05.640","Text":"The epiphyseal plate,"},{"Start":"00:05.640 ","End":"00:09.920","Text":"now, that is going to be a plate that\u0027s in bones, if you remember."},{"Start":"00:09.920 ","End":"00:14.264","Text":"We\u0027re asked here whether it\u0027s arranged as rods or plates,"},{"Start":"00:14.264 ","End":"00:17.939","Text":"we\u0027re asked if it contains the bone\u0027s blood vessels and nerve fibers,"},{"Start":"00:17.939 ","End":"00:20.730","Text":"is responsible for the lengthwise growth of long bones,"},{"Start":"00:20.730 ","End":"00:23.310","Text":"or it synthesizes and secretes matrix."},{"Start":"00:23.310 ","End":"00:29.715","Text":"The same answers that we had in the previous exercise, a previous question."},{"Start":"00:29.715 ","End":"00:33.270","Text":"Let\u0027s see here, what\u0027s our answer going to be?"},{"Start":"00:33.270 ","End":"00:36.015","Text":"It\u0027s certainly not arranged as rods or plates."},{"Start":"00:36.015 ","End":"00:38.660","Text":"The previous question asked about"},{"Start":"00:38.660 ","End":"00:41.925","Text":"the bone\u0027s blood vessels and nerve fibers, it\u0027s not that."},{"Start":"00:41.925 ","End":"00:45.380","Text":"It doesn\u0027t secrete and synthesize matrix,"},{"Start":"00:45.380 ","End":"00:48.740","Text":"so it\u0027s responsible for lengthwise growth of bones."},{"Start":"00:48.740 ","End":"00:53.845","Text":"If you remember the endochondral ossification,"},{"Start":"00:53.845 ","End":"00:57.260","Text":"the making of new bone,"},{"Start":"00:57.260 ","End":"01:00.590","Text":"centers forms in the epiphysis."},{"Start":"01:00.590 ","End":"01:05.390","Text":"In the epiphysis, as you can see over here in"},{"Start":"01:05.390 ","End":"01:11.704","Text":"this picture and there\u0027s the epiphyseal plate,"},{"Start":"01:11.704 ","End":"01:16.140","Text":"which is where all that action occurs."},{"Start":"01:16.140 ","End":"01:20.095","Text":"The answer to our question then is going to be"},{"Start":"01:20.095 ","End":"01:29.875","Text":"the epiphyseal plate is where the lengthwise growth continues until it ossifies."},{"Start":"01:29.875 ","End":"01:32.270","Text":"In this picture as well,"},{"Start":"01:32.270 ","End":"01:36.520","Text":"you can see that the epiphyseal plate here magnifies,"},{"Start":"01:36.520 ","End":"01:40.265","Text":"grows; we have lengthening stages."},{"Start":"01:40.265 ","End":"01:44.600","Text":"When in the lengthening of that plate as you can see,"},{"Start":"01:44.600 ","End":"01:47.620","Text":"there\u0027s this lengthening of the plate."},{"Start":"01:47.620 ","End":"01:50.210","Text":"The answer, therefore,"},{"Start":"01:50.210 ","End":"01:54.020","Text":"is going to be that the epiphyseal plate is responsible"},{"Start":"01:54.020 ","End":"01:59.190","Text":"for the lengthwise growth of the long bones."}],"ID":30335},{"Watched":false,"Name":"Exercise 8","Duration":"1m 32s","ChapterTopicVideoID":28849,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.975","Text":"The cells responsible for bone resorption. What does that mean?"},{"Start":"00:06.975 ","End":"00:12.420","Text":"That means that when the bones are disassembled."},{"Start":"00:12.420 ","End":"00:13.950","Text":"What are the cells responsible for that?"},{"Start":"00:13.950 ","End":"00:15.810","Text":"Are they osteoclasts,"},{"Start":"00:15.810 ","End":"00:20.505","Text":"osteoblasts, fibroblasts, or osteocytes?"},{"Start":"00:20.505 ","End":"00:28.170","Text":"You\u0027ll remember"},{"Start":"00:28.170 ","End":"00:32.235","Text":"blasts usually are precursor cells."},{"Start":"00:32.235 ","End":"00:37.160","Text":"They\u0027re probably not going to be required for resorption."},{"Start":"00:37.160 ","End":"00:43.910","Text":"Our answer therefore is not going to be osteoblasts or fibroblasts."},{"Start":"00:43.910 ","End":"00:46.355","Text":"It\u0027s actually not osteocytes either."},{"Start":"00:46.355 ","End":"00:49.830","Text":"It\u0027s going to be osteoclasts."},{"Start":"00:50.050 ","End":"00:55.220","Text":"Now if you remember, osteoclasts are these large multi-nucleated cells"},{"Start":"00:55.220 ","End":"00:59.540","Text":"that are responsible for dissolution and absorption of bone,"},{"Start":"00:59.540 ","End":"01:03.300","Text":"resorption, the osteoclasts."},{"Start":"01:03.680 ","End":"01:10.970","Text":"They remove bone structure by releasing these enzymes and they help regulate"},{"Start":"01:10.970 ","End":"01:15.170","Text":"calcium concentrations in the body and again bone is"},{"Start":"01:15.170 ","End":"01:19.600","Text":"resorbed for remodeling if when stresses."},{"Start":"01:19.600 ","End":"01:25.145","Text":"Like for instance, you do a lot of exercise or even when bones are broken."},{"Start":"01:25.145 ","End":"01:31.620","Text":"Our answer then is going to be osteoclasts for resorption."}],"ID":30336},{"Watched":false,"Name":"Exercise 9","Duration":"1m 22s","ChapterTopicVideoID":28850,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.850","Text":"Compact bone."},{"Start":"00:02.850 ","End":"00:07.140","Text":"Compact bone is composed of which of the following?"},{"Start":"00:07.140 ","End":"00:09.945","Text":"Trabeculae, compacted collagen,"},{"Start":"00:09.945 ","End":"00:14.670","Text":"osteons, calcium phosphate only?"},{"Start":"00:14.670 ","End":"00:17.430","Text":"When we\u0027re talking about bone, O-S-T,"},{"Start":"00:17.430 ","End":"00:21.975","Text":"ost remember that means bone."},{"Start":"00:21.975 ","End":"00:23.805","Text":"It comes from the Latin,"},{"Start":"00:23.805 ","End":"00:25.995","Text":"so that\u0027s a good guess."},{"Start":"00:25.995 ","End":"00:28.260","Text":"Let\u0027s see what our answer is."},{"Start":"00:28.260 ","End":"00:31.350","Text":"Well, it\u0027s not going to be trabeculae,"},{"Start":"00:31.350 ","End":"00:35.085","Text":"compacted collagen, or calcium phosphate, it is osteons."},{"Start":"00:35.085 ","End":"00:36.435","Text":"Let me remind you."},{"Start":"00:36.435 ","End":"00:42.735","Text":"Compact or cortical bone tissue just forms the hard external layer of all bones,"},{"Start":"00:42.735 ","End":"00:46.025","Text":"that\u0027s the hard part of the bones and there is"},{"Start":"00:46.025 ","End":"00:51.335","Text":"this variant system or they\u0027re called osteons,"},{"Start":"00:51.335 ","End":"00:54.200","Text":"these systems, that\u0027s what we\u0027re being asked."},{"Start":"00:54.200 ","End":"00:56.660","Text":"Yes, so that\u0027s going to be our answer."},{"Start":"00:56.660 ","End":"01:01.790","Text":"You remember that these osteons have these channels,"},{"Start":"01:01.790 ","End":"01:05.600","Text":"these channels that go inside them, these canals,"},{"Start":"01:05.600 ","End":"01:08.900","Text":"the Haversian canals that we saw in"},{"Start":"01:08.900 ","End":"01:12.440","Text":"an earlier exercise and therefore"},{"Start":"01:12.440 ","End":"01:16.384","Text":"our answer to the question of what the compact bone is composed of,"},{"Start":"01:16.384 ","End":"01:21.120","Text":"well, it\u0027s composed of osteons is the best answer."}],"ID":30337},{"Watched":false,"Name":"Exercise 10","Duration":"1m 19s","ChapterTopicVideoID":28851,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.220","Text":"Osteoporosis is a condition where bones become weak and brittle."},{"Start":"00:05.220 ","End":"00:07.455","Text":"We know that in elderly people,"},{"Start":"00:07.455 ","End":"00:13.845","Text":"it is caused by an imbalance in the activity of which of the 2 kinds of cells?"},{"Start":"00:13.845 ","End":"00:19.725","Text":"Osteoclasts and osteoblasts, osteoclasts and osteocytes,"},{"Start":"00:19.725 ","End":"00:24.450","Text":"osteoblasts and chondrocytes, osteocytes and chondrocytes?"},{"Start":"00:24.450 ","End":"00:29.925","Text":"Well, if you remember, osteoclasts are the ones that break down cells."},{"Start":"00:29.925 ","End":"00:34.170","Text":"Osteoblasts are the precursors to the bone tissue,"},{"Start":"00:34.170 ","End":"00:36.495","Text":"so that 1 makes sense."},{"Start":"00:36.495 ","End":"00:39.055","Text":"Let\u0027s look at what answers really are."},{"Start":"00:39.055 ","End":"00:42.560","Text":"Well it\u0027s not osteoclasts and osteocytes."},{"Start":"00:42.560 ","End":"00:44.585","Text":"Osteoblasts and chondrocytes no,"},{"Start":"00:44.585 ","End":"00:47.030","Text":"osteocytes and chondrocytes, certainly not."},{"Start":"00:47.030 ","End":"00:50.240","Text":"Let\u0027s remember the different kinds of cell types."},{"Start":"00:50.240 ","End":"00:53.720","Text":"We\u0027ve got the osteoblasts that form cells, as we said;"},{"Start":"00:53.720 ","End":"00:55.715","Text":"we\u0027ve got the osteocytes,"},{"Start":"00:55.715 ","End":"00:58.325","Text":"they maintain the cell tissue."},{"Start":"00:58.325 ","End":"01:00.725","Text":"We\u0027ve got the osteoclasts."},{"Start":"01:00.725 ","End":"01:03.910","Text":"These are the ones that resorb the bone or break it down."},{"Start":"01:03.910 ","End":"01:05.250","Text":"That\u0027s going to be our answer,"},{"Start":"01:05.250 ","End":"01:07.440","Text":"osteoblasts and osteoclasts,"},{"Start":"01:07.440 ","End":"01:09.290","Text":"and we\u0027ve got these osteogenic cells,"},{"Start":"01:09.290 ","End":"01:11.120","Text":"these stem cells in there."},{"Start":"01:11.120 ","End":"01:18.300","Text":"Our answer then is going to be osteoclasts and osteoblasts."}],"ID":30338},{"Watched":false,"Name":"Exercise 11","Duration":"1m 13s","ChapterTopicVideoID":28852,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.150","Text":"Now in this question we\u0027re asking,"},{"Start":"00:03.150 ","End":"00:06.240","Text":"while assembling a skeleton of a new species,"},{"Start":"00:06.240 ","End":"00:11.430","Text":"a scientist points to one of the bones that they\u0027ve found and"},{"Start":"00:11.430 ","End":"00:18.105","Text":"the scientist observes that it looks like the most likely site of leg muscle attachment,"},{"Start":"00:18.105 ","End":"00:20.549","Text":"so we\u0027ve got muscle attachment to this bone."},{"Start":"00:20.549 ","End":"00:25.980","Text":"What she wants to know is what kind of a bone she\u0027s got there?"},{"Start":"00:25.980 ","End":"00:28.380","Text":"Is it a sesamoid bone,"},{"Start":"00:28.380 ","End":"00:31.485","Text":"a long bone or trabecular bone,"},{"Start":"00:31.485 ","End":"00:33.000","Text":"or a flat bone?"},{"Start":"00:33.000 ","End":"00:35.775","Text":"This is a little bit of a tricky question actually,"},{"Start":"00:35.775 ","End":"00:39.920","Text":"because it\u0027s not entirely clear what this might be."},{"Start":"00:39.920 ","End":"00:45.320","Text":"The answer actually is a flat bone and the reason is that flat bones,"},{"Start":"00:45.320 ","End":"00:50.840","Text":"their primary function is to serve as a point of attachment for muscles."},{"Start":"00:50.840 ","End":"00:55.400","Text":"This question may have been asked in a little bit better way,"},{"Start":"00:55.400 ","End":"00:59.315","Text":"but what I\u0027d like you to remember from this is that"},{"Start":"00:59.315 ","End":"01:09.260","Text":"the primary function of flat bones is to serve as a point of attachment for muscles."},{"Start":"01:09.260 ","End":"01:12.720","Text":"The answer to our question is flat bone."}],"ID":30339},{"Watched":false,"Name":"Exercise 12","Duration":"59s","ChapterTopicVideoID":28853,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:01.730 ","End":"00:06.885","Text":"Synchondroses and symphyses are what?"},{"Start":"00:06.885 ","End":"00:09.465","Text":"This is something we just have to remember,"},{"Start":"00:09.465 ","End":"00:12.060","Text":"what kind of joints are they?"},{"Start":"00:12.060 ","End":"00:17.835","Text":"Well, both of these have cartilage in them,"},{"Start":"00:17.835 ","End":"00:21.840","Text":"so they\u0027re cartilaginous joints."},{"Start":"00:21.840 ","End":"00:27.240","Text":"Yes, let\u0027s remember this from figures that we\u0027ve seen before,"},{"Start":"00:27.240 ","End":"00:32.504","Text":"if you remember synchondroses are these cartilaginous."},{"Start":"00:32.504 ","End":"00:40.400","Text":"Yes, they have bones that are completely joined by hyaline cartilage so that\u0027s correct,"},{"Start":"00:40.400 ","End":"00:46.045","Text":"and symphyses are also connected by cartilage."},{"Start":"00:46.045 ","End":"00:48.890","Text":"Yes, symphyses that we find, for instance,"},{"Start":"00:48.890 ","End":"00:52.235","Text":"in the pelvic area and in the vertebra."},{"Start":"00:52.235 ","End":"00:58.620","Text":"Our answer to this question is going to be cartilaginous joints."}],"ID":30340},{"Watched":false,"Name":"Exercise 13","Duration":"26s","ChapterTopicVideoID":28854,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:07.215","Text":"The movement of bone away from the midline of the body is called which of the following?"},{"Start":"00:07.215 ","End":"00:11.745","Text":"Circumduction, extension, adduction, or abduction?"},{"Start":"00:11.745 ","End":"00:14.730","Text":"Again, this is something that we just need to remember,"},{"Start":"00:14.730 ","End":"00:17.055","Text":"it\u0027s going to be abduction."},{"Start":"00:17.055 ","End":"00:22.830","Text":"Abduction is when a bone moves away from the midline of the body."},{"Start":"00:22.830 ","End":"00:26.410","Text":"Yes, abduction."}],"ID":30341},{"Watched":false,"Name":"Exercise 14","Duration":"1m 10s","ChapterTopicVideoID":28855,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.080 ","End":"00:06.525","Text":"Which of the following is not a characteristic of the synovial fluid?"},{"Start":"00:06.525 ","End":"00:08.910","Text":"Not a characteristic."},{"Start":"00:08.910 ","End":"00:12.195","Text":"Is it lubrication, shock absorption,"},{"Start":"00:12.195 ","End":"00:14.970","Text":"regulation of water balance in the joints,"},{"Start":"00:14.970 ","End":"00:20.050","Text":"or protection of the articular cartilage?"},{"Start":"00:21.140 ","End":"00:24.090","Text":"The fluid is certainly for lubrication,"},{"Start":"00:24.090 ","End":"00:25.829","Text":"it\u0027s certainly for shock absorption,"},{"Start":"00:25.829 ","End":"00:28.395","Text":"and it also protects the cartilage."},{"Start":"00:28.395 ","End":"00:32.670","Text":"Our answer certainly is going to be regulation of water balance in the"},{"Start":"00:32.670 ","End":"00:37.515","Text":"joint because that\u0027s not a characteristic of the fluid."},{"Start":"00:37.515 ","End":"00:41.300","Text":"Let\u0027s look at the figure that we might remember."},{"Start":"00:41.300 ","End":"00:44.440","Text":"This is the synovial joint."},{"Start":"00:44.440 ","End":"00:48.260","Text":"They are capable of the greatest movements, and again,"},{"Start":"00:48.260 ","End":"00:54.710","Text":"the fluid which is in the synovial joint,"},{"Start":"00:54.710 ","End":"00:57.710","Text":"is going to be there for lubrication,"},{"Start":"00:57.710 ","End":"00:58.955","Text":"to reduce the friction,"},{"Start":"00:58.955 ","End":"01:05.265","Text":"allow greater movement and it protects the cartilage that\u0027s there,"},{"Start":"01:05.265 ","End":"01:10.710","Text":"so our answer is not to regulate water balance in the joints."}],"ID":30342},{"Watched":false,"Name":"Exercise 15","Duration":"36s","ChapterTopicVideoID":28856,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.570","Text":"The elbow is an example of which type of joints."},{"Start":"00:03.570 ","End":"00:07.230","Text":"There are different kinds of joints;"},{"Start":"00:07.230 ","End":"00:10.020","Text":"hinge, pivot, saddle, gliding."},{"Start":"00:10.020 ","End":"00:12.090","Text":"This is actually an easy one."},{"Start":"00:12.090 ","End":"00:13.950","Text":"It\u0027s going to be a hinge."},{"Start":"00:13.950 ","End":"00:17.235","Text":"It goes back and forth like a hinge."},{"Start":"00:17.235 ","End":"00:21.180","Text":"Yes. Remember, this is hinge joints are slightly"},{"Start":"00:21.180 ","End":"00:25.755","Text":"rounded and we\u0027ve got a hinge over here in the elbow."},{"Start":"00:25.755 ","End":"00:28.215","Text":"That\u0027s going to be our answer."},{"Start":"00:28.215 ","End":"00:32.595","Text":"Specifically, we learned that the elbow is a hinge joint."},{"Start":"00:32.595 ","End":"00:36.130","Text":"Our answer is hinge."}],"ID":30343},{"Watched":false,"Name":"Exercise 16","Duration":"1m 17s","ChapterTopicVideoID":28857,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.720","Text":"A high ankle sprain is an injury caused by an overstretching of"},{"Start":"00:03.720 ","End":"00:08.235","Text":"the ligaments that connect the tibia and fibula."},{"Start":"00:08.235 ","End":"00:11.985","Text":"You remember these are the bones in the lower part of the leg."},{"Start":"00:11.985 ","End":"00:15.660","Text":"What type of joint is involved in the sprain?"},{"Start":"00:15.660 ","End":"00:21.075","Text":"This is again something we just need to remember the names of these different joints."},{"Start":"00:21.075 ","End":"00:22.905","Text":"Is it ball and socket,"},{"Start":"00:22.905 ","End":"00:27.990","Text":"gomphosis, syndesmosis or symphysis?"},{"Start":"00:27.990 ","End":"00:33.554","Text":"Well, it is certainly not a ball and socket."},{"Start":"00:33.554 ","End":"00:36.375","Text":"It\u0027s not gomphosis and it\u0027s not symphysis."},{"Start":"00:36.375 ","End":"00:41.450","Text":"It\u0027s syndesmosis, if you remember,"},{"Start":"00:41.450 ","End":"00:43.730","Text":"that\u0027s a slightly movable joints where the bones are"},{"Start":"00:43.730 ","End":"00:47.060","Text":"connected by a band of connective tissue."},{"Start":"00:47.060 ","End":"00:51.125","Text":"Specifically, for instance, between the tibia and fibula."},{"Start":"00:51.125 ","End":"00:54.335","Text":"Yes, they can move with respect to each other,"},{"Start":"00:54.335 ","End":"01:00.035","Text":"but there is a lot of ligaments between the 2 keeping that from happening."},{"Start":"01:00.035 ","End":"01:06.590","Text":"Specifically, this is between the tibia and the fibula in the leg,"},{"Start":"01:06.590 ","End":"01:11.225","Text":"and also the radius and ulna in the forearm."},{"Start":"01:11.225 ","End":"01:16.320","Text":"Our answer is going to be syndesmosis."}],"ID":30344},{"Watched":false,"Name":"Exercise 17","Duration":"1m 3s","ChapterTopicVideoID":28858,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.285","Text":"In relaxed muscle, the myosin binding site on actin is blocked by which of the following?"},{"Start":"00:06.285 ","End":"00:07.500","Text":"Is it titin,"},{"Start":"00:07.500 ","End":"00:12.105","Text":"troponin, myoglobin or tropomyosin?"},{"Start":"00:12.105 ","End":"00:18.615","Text":"Well, the only thing that\u0027s possible really would be troponin or tropomyosin."},{"Start":"00:18.615 ","End":"00:20.820","Text":"It\u0027s going to be tropomyosin."},{"Start":"00:20.820 ","End":"00:26.650","Text":"Let\u0027s remember tropomyosin is in the thin filaments,"},{"Start":"00:26.660 ","End":"00:32.115","Text":"it\u0027s primarily component of filament which is mostly actin,"},{"Start":"00:32.115 ","End":"00:37.825","Text":"and it is a binding site for myosin attachment."},{"Start":"00:37.825 ","End":"00:42.170","Text":"Strands of tropomyosin block the binding sites and they"},{"Start":"00:42.170 ","End":"00:47.240","Text":"prevent the actin-myosin interactions when the muscles are at rest."},{"Start":"00:47.240 ","End":"00:54.530","Text":"The answer therefore is going to be that tropomyosin is going to"},{"Start":"00:54.530 ","End":"01:02.310","Text":"be the one that blocks the myosin binding sites on the actin."}],"ID":30345},{"Watched":false,"Name":"Exercise 18","Duration":"40s","ChapterTopicVideoID":28859,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.005","Text":"The cell membrane of a muscle fiber is called what?"},{"Start":"00:04.005 ","End":"00:08.700","Text":"I\u0027m talking about the cell membrane of a muscle fiber."},{"Start":"00:08.700 ","End":"00:10.680","Text":"It\u0027s not a myofibril,"},{"Start":"00:10.680 ","End":"00:14.100","Text":"it\u0027s not going to be sarcoplasm,"},{"Start":"00:14.100 ","End":"00:15.539","Text":"and not myofilament."},{"Start":"00:15.539 ","End":"00:17.175","Text":"It\u0027s the sarcolemma."},{"Start":"00:17.175 ","End":"00:18.368","Text":"If you remember,"},{"Start":"00:18.368 ","End":"00:23.580","Text":"the sarcolemma is the plasma membrane of a skeletal muscle fiber."},{"Start":"00:23.580 ","End":"00:24.750","Text":"Here\u0027s some muscle fiber."},{"Start":"00:24.750 ","End":"00:31.260","Text":"Remember they\u0027re the microfibrils inside and they are these multinucleated cells."},{"Start":"00:31.260 ","End":"00:37.245","Text":"But the membrane on the outside of the whole business is this sarcolemma."},{"Start":"00:37.245 ","End":"00:40.480","Text":"That\u0027s our answer for this question."}],"ID":30346},{"Watched":false,"Name":"Exercise 19","Duration":"1m 27s","ChapterTopicVideoID":28860,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.165","Text":"We know that the muscle relaxes if no new nerve signal arrives."},{"Start":"00:06.165 ","End":"00:10.425","Text":"There\u0027s no new nerve signal and then muscles relax."},{"Start":"00:10.425 ","End":"00:12.480","Text":"However, the neurotransmitter from"},{"Start":"00:12.480 ","End":"00:16.710","Text":"the previous stimulation or could keep the muscle contracting,"},{"Start":"00:16.710 ","End":"00:19.615","Text":"because it\u0027s still present in the synapse."},{"Start":"00:19.615 ","End":"00:22.410","Text":"What stops this is our question."},{"Start":"00:22.410 ","End":"00:27.165","Text":"The activity of which of the following helps remove the neurotransmitter."},{"Start":"00:27.165 ","End":"00:30.405","Text":"First let\u0027s think about what\u0027s the neurotransmitter."},{"Start":"00:30.405 ","End":"00:36.765","Text":"Remember, acetylcholine is going to be the neurotransmitter."},{"Start":"00:36.765 ","End":"00:39.780","Text":"Our answer to this question is not myosin,"},{"Start":"00:39.780 ","End":"00:42.225","Text":"not action potential, not tropomyosin."},{"Start":"00:42.225 ","End":"00:45.195","Text":"It\u0027s going to be acetylcholinesterase."},{"Start":"00:45.195 ","End":"00:50.855","Text":"A-S-E indicates that it\u0027s an enzyme, and what does it do?"},{"Start":"00:50.855 ","End":"00:55.380","Text":"It\u0027s going to digest acetylcholine."},{"Start":"00:55.550 ","End":"00:59.585","Text":"Let\u0027s look at the figure of this to remind you."},{"Start":"00:59.585 ","End":"01:08.570","Text":"Acetylcholine is going to be what\u0027s going to be coming out in the synapse."},{"Start":"01:08.570 ","End":"01:13.160","Text":"It\u0027s going to be released by the motor neurons and it binds the receptors."},{"Start":"01:13.160 ","End":"01:16.880","Text":"That\u0027s what\u0027s going to cause the muscle to become"},{"Start":"01:16.880 ","End":"01:21.170","Text":"depolarized and then the muscle ultimately contract."},{"Start":"01:21.170 ","End":"01:26.730","Text":"The answer to our question is going to be acetylcholinesterase."}],"ID":30347},{"Watched":false,"Name":"Exercise 20","Duration":"1m 12s","ChapterTopicVideoID":28861,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.825","Text":"The ability of a muscle to generate tension,"},{"Start":"00:03.825 ","End":"00:10.230","Text":"that\u0027s when a muscle moves or is exerting force,"},{"Start":"00:10.230 ","End":"00:13.275","Text":"immediately after stimulation is dependent on what?"},{"Start":"00:13.275 ","End":"00:17.130","Text":"Think of a bodybuilder who is trying to exert force on something,"},{"Start":"00:17.130 ","End":"00:20.535","Text":"say to raise weight or something like that."},{"Start":"00:20.535 ","End":"00:22.050","Text":"What\u0027s this dependent on?"},{"Start":"00:22.050 ","End":"00:24.135","Text":"Myosin interaction with the M line,"},{"Start":"00:24.135 ","End":"00:26.250","Text":"overlap of myosin and actin,"},{"Start":"00:26.250 ","End":"00:30.735","Text":"actin attachments to the Z line."},{"Start":"00:30.735 ","End":"00:35.750","Text":"Well, let\u0027s remember what our answer might be."},{"Start":"00:35.750 ","End":"00:42.200","Text":"Actually, it\u0027s none of the above is the answer because in individual muscle fibers,"},{"Start":"00:42.200 ","End":"00:46.505","Text":"the amount of tension produced depends on the cross-sectional area."},{"Start":"00:46.505 ","End":"00:50.350","Text":"In other words, how big is the muscle altogether,"},{"Start":"00:50.350 ","End":"00:52.670","Text":"of the actin and myosin fibers,"},{"Start":"00:52.670 ","End":"00:56.810","Text":"the cross-sectional area, as well as the frequency of neural stimulation?"},{"Start":"00:56.810 ","End":"01:00.200","Text":"Of course, the more frequently it gets neural stimulation,"},{"Start":"01:00.200 ","End":"01:04.460","Text":"the more tension is going to be produced."},{"Start":"01:04.460 ","End":"01:06.545","Text":"At the end of the day,"},{"Start":"01:06.545 ","End":"01:11.310","Text":"our answer is going to be none of the above in this question."}],"ID":30348},{"Watched":false,"Name":"Exercise 21","Duration":"1m 34s","ChapterTopicVideoID":28862,"CourseChapterTopicPlaylistID":292702,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.945","Text":"In this exercise, we\u0027re going to try to understand"},{"Start":"00:03.945 ","End":"00:08.820","Text":"what the purpose or what the mechanism of Botox is."},{"Start":"00:08.820 ","End":"00:12.750","Text":"Botulinum toxin causes flaccid paralysis,"},{"Start":"00:12.750 ","End":"00:15.150","Text":"it causes a paralysis of muscles,"},{"Start":"00:15.150 ","End":"00:19.289","Text":"and is used for cosmetic purposes under the name Botox."},{"Start":"00:19.289 ","End":"00:25.260","Text":"Which of the following is most likely the mechanism of the action of Botox?"},{"Start":"00:25.260 ","End":"00:30.795","Text":"Is that the Botox decreases the production of acetylcholinesterase?"},{"Start":"00:30.795 ","End":"00:35.180","Text":"Remember that\u0027s the enzyme that destroys acetylcholine."},{"Start":"00:35.180 ","End":"00:41.690","Text":"Acetylcholine is the neurotransmitter that causes muscle contraction."},{"Start":"00:41.690 ","End":"00:48.455","Text":"Is it going to decrease the production of what stops the muscles from contracting,"},{"Start":"00:48.455 ","End":"00:52.640","Text":"or does it increase calcium release from the sarcoplasmic reticulum"},{"Start":"00:52.640 ","End":"00:56.885","Text":"or does it block ATP binding at the site in actin,"},{"Start":"00:56.885 ","End":"01:02.315","Text":"or does it decrease the release of acetylcholine from motor neurons?"},{"Start":"01:02.315 ","End":"01:07.565","Text":"Well, our answer is going to be d. Let\u0027s remember that"},{"Start":"01:07.565 ","End":"01:12.919","Text":"acetylcholine is released by motor neurons and binds the receptors."},{"Start":"01:12.919 ","End":"01:19.580","Text":"Yes, its own receptors on the motor end and depolarizes sarcolemma starting contraction."},{"Start":"01:19.580 ","End":"01:23.330","Text":"In order to stop that contraction to make paralysis,"},{"Start":"01:23.330 ","End":"01:27.589","Text":"the way the Botox works is that it simply"},{"Start":"01:27.589 ","End":"01:33.660","Text":"decreases the release of the acetylcholine from the motor neurons."}],"ID":30349}],"Thumbnail":null,"ID":292702}]

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