0:06 hello in this video we will look at the
0:09 skeletal system which is the system of
0:11 the bones and we have many different
0:14 types of bones in our body with all
0:17 shapes and sizes we have flat bones such
0:19 as the sternum we have your regular
0:23 bones such as the vertebrae we have
0:26 short bones where which are the carpal
0:29 bones in the hand we have sesamoid bones
0:32 such as our patella kneecap and long
0:37 bones such as the humerus bones are hard
0:41 as we know however if you look at the
0:43 humerus here the inside of the bone is
0:47 actually not as hard this is a spongy
0:50 bone which is trabecular bone making up
0:54 the inner bone it is the compact bone
0:55 that is dense
0:58 it's the dense bone made up of osteons
1:03 this is the outer bone the long bone
1:05 such as the humerus has have different
1:09 sections so the very ends of the long
1:11 bone is the epiphyses then the
1:14 metaphysis which separate the ends of
1:17 the long bone to the center of the bone
1:19 now the center of the bone the bowed
1:25 shaft is called the diaphysis the inside
1:27 of the bone the center of the bone
1:29 should I say can be hollow and this is
1:31 the medulla which can contain bone
1:34 marrow let's look at another example
1:37 let's look at the flat bone such as the
1:40 sternum here but let's mainly look
1:42 inside the manubrium which is the top
1:47 part of the sternum just like the long
1:50 bone the outside is may is the compact
1:53 bone the hard one and the center the
1:56 small inside of the bone is a spongy
2:00 bone which is the trabeculae bone so I
2:02 hope you get an appreciation that there
2:07 is compact or spongy bone let us cut a
2:10 cross-section of the humerus the hollow
2:12 Center here the cavity is the medulla
2:15 there are many cells that actually make
2:17 up the bone which play an important
2:21 not only in making the boat strong and
2:23 to keep for you to help us with posture
2:26 and movement but the cells within the
2:29 bones are very important in the
2:33 homeostatic levels you can say of
2:36 minerals such as calcium and phosphate
2:38 now cells of the bone include
2:40 osteoblasts which are the cells
2:43 responsible for building our bones
2:46 there are also osteoclasts which are
2:49 cells responsible for breaking down bone
2:53 there is also osteocytes which are which
2:55 are mature bones which are mature bone
2:59 cells from from trapped osteoblasts so
3:01 they are osteoblasts and they become
3:04 trapped in their own matrix forming
3:08 osteocytes you also have osteoprogenitor
3:10 cells which are cells that essentially
3:15 become osteoblasts there are there are
3:17 also cells that are made from our bone
3:19 marrow such as our such as our immune
3:22 cells but we won't talk about that here
3:25 now let's draw another the same cross
3:27 section of the long bone with the
3:30 medulla now let's see how these cells
3:32 that we just talked about actually make
3:35 up the bone so looking at compact well
3:38 here we have osteocytes which are the
3:41 mature bone cells remember they become
3:44 osteocytes when the osteoblasts are
3:47 trapped within the matrix then on the
3:50 very outside are the actual osteoblasts
3:51 which are cells that are building the
3:55 bone secreting matrix again when these
3:57 osteoblasts become trapped in the bone
4:00 matrix they actually become osteocytes
4:04 and form the compact bone surrounding
4:08 the compact bone all together is a layer
4:11 called the periosteum now the periosteum
4:14 is separated into a fibrous layer and a
4:17 cellular layer which is the layer where
4:20 we find the osteoprogenitor cells and
4:23 osteoblasts surrounding the periosteum
4:26 are the blood vessels which penetrate
4:29 the bone through canals and
4:32 which allows it to supply the inside of
4:35 the bone it is important to know that
4:37 the bone itself does not actually have
4:45 now let's zoom or closer to the compact
4:48 bone and spongy bone area to look at to
4:51 look at how these how bone is organized
4:54 in a from a different angle so here
4:56 again is a spongy bone which is the
4:59 inner bone and then we have the outer
5:02 compact bone the hard bone surrounding
5:04 the compact bone is the certain the bone
5:06 all together that is a periosteum which
5:09 is pain sensitive remember and
5:12 surrounding the periosteum are the blood
5:14 vessels the arteries and veins and the
5:16 arteries and veins can penetrate inside
5:18 the bone to supply the inner bone as
5:22 well the blood vessels travel from the
5:24 outside to the inside of the bone
5:28 through canals now remember the compact
5:30 bone is mainly made up of trapped
5:33 osteoblasts which are the osteocytes
5:36 they are actually organized into an
5:38 osteon which are the functional units of
5:42 compact bone if we pull out one of these
5:45 osteons we can find this central canal
5:49 which houses blood vessels and this is
5:53 how the bone stays nourished anyway I
5:55 hope you enjoyed this video on an
5:57 introduction to the skeletal system and
6:00 the structure and an anatomy of the bone
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