Full transcript
0:00This model is a representation of the
0:02microscopic structures found in compact
0:04bone.
0:05This area here right here is
0:07representing the compact bone, while
0:09this area here is representing the
0:11spongy bone. Notice that the compact
0:14bone is surrounded by a membrane known
0:17as the periosteal membrane, which must
0:19be attached by Sharpey's fibers or
0:22perforating fibers. These fibers are
0:25made up of a very important molecule
0:27known as collagen.
0:33The membrane that surrounds the spongy
0:36bone is known as the endosteal membrane.
0:40Now, the functional unit of bone is
0:43known as the osteon or Haversian system.
0:46So, this right here is one Haversian
0:48system or osteon. So is this one and
0:51this one here and this one and this one
0:53as well. That's an entire Haversian
0:56system or osteon just as this one is as
0:58well. Okay? Now, bone itself up of
1:03layers and these layers are known as
1:05lamella. This lamella has been pulled
1:07out in this model so you can see it
1:09better. So, this lamella that is
1:11sticking out there and that is closest
1:13to the periosteal membrane is known as
1:15the circumferential lamella, while the
1:18lamella found within the osteon are
1:20known as concentric lamella.
1:23Now, of course this tissue must be
1:25maintained. It's a living tissue. It
1:27must have cells. So, this tiny little
1:29structures that you see here that look
1:31like little ants are actually the
1:33osteocytes, which simply maintain the
1:35bone matrix.
1:37These osteocytes, since they're in a
1:40hard matrix, must be lying within a
1:43depression within the bone and these
1:45depressions are known as lacunae.
1:49You also will notice that there are tiny
1:51little legs that come off of these
1:54osteocytes, but actually these are
1:56processes of the cells.
1:58So, there are these tiny little
2:01hair-like depressions within each osteon
2:05or Haversian system. These little lines
2:07that you see are actually known as
2:09canaliculi. The important function of
2:11the canaliculi is to allow for the
2:14for the blood vessels that are carrying
2:17the blood here is to allow the blood
2:19within the blood vessels to allow the
2:21nutrients to move from this area on to
2:25the osteocytes. So, essentially, the
2:27nutrients are moving from a higher
2:29concentration within the blood vessel
2:32and therefore moving to a lower
2:33concentration. So, via the canaliculi,
2:36the each osteocyte can actually get
2:39nutrients. Very, very important.
2:42Um one important another important uh
2:45structure that I want you guys to
2:46remember are the canals that run
2:49horizontally. These canals are known as
2:52perforating canals or Volkmann's canals.
2:55And notice that they are connected
2:56vertically now
2:58with what? Well, perpendicularly
3:01actually. Uh connected with a central
3:05uh canal or Haversian canal.
3:09And let's see, is there anything else?
3:11Uh one interesting thing to note is you
3:14can see the orientation of these lines
3:16is actually representing the orientation
3:18of collagen that makes up the bone. So,
3:22you see that the lines are going in the
3:24opposite directions and the purp-
3:26purpose of that is to render a lot of
3:29strength to bone.
3:30Well, I hope that helps you and uh
3:33enjoy. Bye.