Full transcript
0:00we're gonna look at a different model to
0:03see the same structures that we just saw
0:05now on this model you'll notice it kind
0:08of looks like a pizza wedge slice and we
0:11can see it from the top or from the side
0:14here now when we look at it from the top
0:16we notice all of these big circular
0:19rings these are the individual osteons
0:23like we just saw in that previous model
0:25notice how in the center of each osteon
0:28we have our central canals and if we
0:31look at the model from the side we can
0:34see all of the central canals running up
0:37through that central lis located area on
0:41our osteon now if we set it back down
0:44here around our osteon we have our
0:47concentric lamellae those are going
0:49around the central canal and notice how
0:52each osteon has a different number of
0:54concentric lamellae so they can vary
0:57between osteons now these two osteons
1:00here they kind of look like cake toppers
1:02but if we turn it from the side we can
1:05see that each of these layers is one of
1:09our concentric lamellae we've simply
1:11just pulled them up to show them off a
1:13little bit easier one thing I always
1:16like to point out to students is notice
1:18how the collagen fibers run in
1:21alternating directions in each
1:23concentric lamellae this increases the
1:27strength of compact bone because the
1:29fibers overlap one another in between
1:33the concentric lamellae we can see art
1:35lacunae the small pits and we can also
1:38if we get really close we can see those
1:41little canaliculi now this model shows
1:44us a couple of other structures that are
1:46present on compact bone we can see our
1:49two membranes this is the inside of the
1:52bone and this is the outside of the bone
1:55if we look on the inside of the bone
1:57notice this gray membrane here this is
2:01called the end ostium and though means
2:03inside
2:04osteo means bone so inside bone membrane
2:08going around the outside we
2:11have the periosteum Perry means a round
2:15osteo means bone so the periosteum is
2:18the membrane that goes around the entire
2:20outside of the bone now the periosteum
2:23is important because it's going to lay
2:25down new layers of bone which we can see
2:28here these are called the
2:30circumferential lamellae and if I turn
2:33it on its side you can see a couple of
2:34those circumferential lamellae have been
2:36pulled up and out of the model now a
2:39circumference is the distance around a
2:42circle
2:43so these circumferential lamellae travel
2:46around the entire circumference of the
2:48bone so they go around the entire
2:50outside there's two other structures we
2:53can see on this one and we're going to
2:55see them by turning the model on its
2:57side notice how we have this blood
2:59vessel here that's traveling
3:01horizontally through the bum this is
3:04called a perforating canal or Volks minh
3:07canal this carries blood vessels and
3:10nerves into the bone and hooks up with
3:12each of these central canals we can also
3:16see that our periosteum this outer
3:19membrane is held on to the bone by
3:21perforating fibres the perforating
3:24fibres Pierce into the bone and
3:26essentially anchor this in place this is
3:29why when muscles and tendons pull on our
3:32periosteum
3:32it doesn't just rip off of the bone