Intervertebral disc (anatomy)

right this week we is doing the intervertebral discs to the discs between the vertebra there are a lot of them this is kind of my one of my comfortable places because I used to be a college biologist and we got some funky ecology connective tissue stuff going on in here see a little bit more with this I know what I can use this for I know a lot of models showing the same thing but I can get to different bits on different models and they do show slightly different things lovely and these are the models of 10th fall over so the intervertebral discs why are they there what do they do what's their structure and what happens when they fail actually there are a few things to notice to start with so if we look along the vertebral column here we see lots of intervertebral discs and we notice that the interval intervertebral discs up in the cervical region are smaller than the intervertebral discs down in the lumbar region these are much larger and we also see a difference in the thorax so the intervertebral discs the joint between these bones allows a little bit of movement each joint allows a little bit but when you add all of these bones up you get quite a big range of movement only so that's what needs fertile discs are for so that's that's one purpose of the intervertebral joints these are joints between bones and we want these bones to move because then we can move this is the ACL skeleton pretty much everything is hanging off and we have quite a lot of movement in the neck in the cervical region it's highly mobile isn't it we don't have so much movement in the thoracic region and then we have a lot of movement again in the lumbar region right you know for bowing to the Queen and stuff the joint between the vertebrae so the intervertebral joint comprises the intervertebral discs and a whole bunch of ligament which we talked about the ligaments elsewhere probably if not I'll add it to my list but the intervertebral disk then is also a shock absorber so we've got a lot of weight going through the vertebral column and we're walking and running and jumping and that sort of thing we get load and some of that load is applied quite rapidly so we get shock so these are actually squidgy pads these intervertebral discs so they absorb that shock and we'll talk about how they're squidgy pads and how that works in a bit I'm gonna shut those blinds because that's really bright isn't it it's a bit better I think the anatomy lab should have a lot of natural light because of the things we're looking at it looks so much better but have a little bit of lighting control give for this right where was really so these intervertebral discs are deformable which means that when you're stood up all day they slowly compress they get squashed so you get a bit shorter during the day and then at night when you're led down and in olives anymore they they get a little bit long as you get a bit taller every night in a bit shorter that's pretty one of the reasons we get shorter with age not so much because of that but because of changes to the connective tissue and these joints get called secondary cartilaginous joints also a synthesis so we see syntheses we see these symphysis joints in the midline here the big one is the pubic symphysis right down here here's the pubic symphysis right so these are all in the midline these are all secondary cartilaginous joints symphysis joints now have you ever looked at a skeleton and noticed that although we've got all these intervertebral discs there isn't one I'll pick the best garden to do this with but there isn't one so I mean different things showing different things there's see one there's see two so Atlas and axis the top two cervical vertebrae there's no intervertebral this between them there is between C 2 & 3 & 3 & 4 moons is all the way down but not between c1 and c2 vertebrae also down the other end the last intervertebral disc is between the l5 vertebra the last lumbar vertebra and the first sacral vertebra and then there aren't any functioning intervertebral discs in the sacrum and there aren't any intervertebral discs in the coccyx all right so we there aren't intervertebral discs between every vertebral intervertebral joint I would put money on something falling over before the end of this video now each individual disc has quite a cool and quite simple structure it has an annulus fibrosus a ring around the outside it's the bit we can see here this is the annulus fibrosus and the Angliss fibrosis is largely type 1 collagen so it's making concentric so rings of sheets of collagen and it's got fibroblasts in there maintaining that collagen so it's making a ring hence annulus because ring anus means ring right so annulus fibrosus it's a fibrous ring around the outside of the intervertebral disc so that's very good at resisting tensile forces all right so it doesn't really want to it doesn't want to stretch it's very good at keeping it its round shape but it's not so good at compressible forces you know if you if you squash it in light in this direction that's the angular's fibrosis this lugging loads of collagen not a lot of proteoglycans and the collagen fibers are running like this direction right so they're running they're not running in a ring around there they're kind of running like this there's one layer like that and there's another layer like that so it's really really tough you know it's like a bloody Kevlar vest or something you know it's a really really tough material I mean inside here in there we have the nucleus pulposus which is the gel bit that's the very squidgy bit and that is a bit more like cartilage it's filled with Type 2 collagen loads of proteoglycans loads of agar can and then the cells in there are a bit more chondrocyte like they're a little bit more cartilage cell like because they're maintaining all all that stuff and also actually interestingly the intervertebral disc is a vascular there are no blood vessels running into it just like cartilage there are blood vessels within the bone and where the so if we the body of the vertebra the vertebral body here the the cap of it like the top of it with the bit that is interfacing the bit that joins to the intervertebral disc that gets called the end plate and that's got a load of capillaries in it blacks where they end which means the nutrients and oxygen and co2 stuff have got to diffuse through the intervertebral discs to nourish the cells and remove metabolites just like in cartilage so the cells in here are very good at being hypoxic they're quite cool in a low low oxygen environment they're quite happy with that now what we have so in here but all of those cool things going in is that the type 2 collagen doesn't form a sheet it makes like a mesh like a string bag and inside that string bag you have a and proteoglycan and what that what angle can is good at is is pulling water in very hydrophilic so it sucks the water in and holds on to it so now you've got you've got like a mesh bag of balloons right so if you if you squid if you push down on that on the nucleus pulposus you're pushing down on water there's being held on to by Agra can they can't get squished away because the Anglicans being held in place by all the collagen right so you get this really really good compressible gel so your squidgy its deformable and then it goes back to its original shape so that's the shock absorbing bit so that the nucleus pulposus nucleus yeah Pol Pot yeah is in the middle that's the shock absorbing bit and it's held in place then by the annulus fibrosus that's the job the annulus fibrosus Bannister it's keep squidgy bit in the middle and it's when the annulus fibrosus fails a squeegee bit gets out you start to have problems with the intervertebral discs and with your back and pain and stuff incidentally that the end plate the the surface of the vertebral body that's articulating with the intervertebral discs is covered with our hyaline cartilage you're going to got bone collagen vertebral disc it's proper joint right which is good because these things got last a long time they got do a lot of work mine yeah mine gave it tight sometimes right so the nucleus pulposus then gets squashed by lotus I'm standing up gravity the weight of my body is is squashing the nucleus pulposus it's got a little bit of load on it now if I was to lift a weight if I was carrying two big bags of shopping I'd be increasing the load on my nucleus proposes to get squished a bit more I think the worst thing you can or the most loads you can do is like if you're if you if you're sat down and then you lean forward and then you've got weights in your arms and I'm bending my that's when you like you load some of these intervertebral discs nucleus pulposus is maximally that's like a bad thing to do and then of course load is lowest when you're when you're led down when or if you're in space so hopefully you know that you've got to be careful when lifting heavy loads I'll show you why so when you you want to you want to keep your back nice and straight and course we say straight though the back isn't straight it's it's cursed right it's this guy's quite heavily curved but the back does have a curve to it by straight you know you mean standing up straight like your mother told you to do when you were little so when you're lifting a heavy load you want to keep your back in that kind of neutral position you only feel your legs your legs are strong that's why they call these big muscles we were looking at is actually you can lift things you don't want to bend your back and then and then lift things cuz that is going to cause you problems the reason why is what we're really the the the intervertebral discs the most commonly damaged in this way are the the the intervertebral discs between the lumbar vertebrae and I think is most commonly like these lower ones right between l4 and l5 or l5 and s1 and if only right see this disc look what happens when I bend my back so look this side is getting really squashed and this side is not getting squash means there's a load and load of compression here way too much compression which means that the nucleus pulposus wants to try to get it's getting pushed that way it's getting squashed postie really right i mean if you have an Oreo right and you squidge it at one end what happens to the cream okay I can't do that demo we can't bring food into the lab but there so that's what you tend to see is that if the the nucleus pulposus is under a lot of compression a really high compressive load and there's a weakness in the annulus fibrosus the ring that's supposed to be retaining and holding the nucleus pulposus in place the nucleus pulposus will get either will either cause a bulge in the annulus fibrosus which is supposed to be attached in the bone here but if there's a weakening my bulge outward or in my burst in might herniate completely new you get nucleus pull posters pushing out through the annulus which is what you see here and this leads to another bit of anatomy to consider with the intervertebral discs is that look we've got these spinal nerves popping out here so the now is an intervertebral foramen now in the vertical form and that's an intervertebral foramen much of the intervertebral foramen x' walls are made up by adjacent vertebrae right but look the anterior the anterior wall of that intervertebral foramen is formed by the intervertebral discs so if the nucleus pulposus herniates out through the fibrosis if the intervertebral discs herniates which is what we see here we get this bulge it's gonna press on the spinal nerve it is coming through the intervertebral foramen which is why this is so bad and of course we've got the the spinal cord which becomes the cord recliner at this level posterior which means that if we get a what's called a slipped disc it's not really a slipped disc is it it's a it's a herniated intervertebral disc if it fails then it might push out on to the spinal cord or the cord requirement depending upon the level so you gotta watch out for those symptoms but it's it but because that's kind of reinforced by ligaments and what-have-you it's more likely to protrude postural laterally so onto the onto the spinal nerve so this is gonna cause a lot of pain some of the pain is going to be caused by damage to the annulus fibrosus which has some sensory fibers around the outside so the pain is going to be caused by inflammation in the local area and some of the pain that's got like the local pain but then and some of the pains gonna be caused by irritation to the nerve but that's where you get you know like pains in the lower limb referred pain because as the nerve gets compressed it gets irritated the pain is perceived in whatever region of the body is being innovated by that nerve if it's low down in the back then we're talking the lower limbs don't we so discs in young people tend to be really strong its whole intervertebral discs and intervertebral joint thing tends to be really strong so if your lifts badly you might get away with it when you're young but it's not recommended because if you're still if you push your hard enough you're still damaged yourself but as we get older as we as we see elsewhere in the body connective tissue gets a bit Crapper as we get older fibroblasts seem to get less active and what-have-you and what we see in the intervertebral discs is they hold less water I think the protein content goes down the disc becomes more like fibrocartilage so it gets stiffer all those important compressible deformable so there's a lot of fun there's a lot of tissue air there's a lot of engineering and physics terms going up going up going on in here like deformability and creep and once you have a good one hysteresis so anyway as we get older as he's become more a fiber Carla fibrocartilage and less like in diverse produce they have less water and that that normal function of the youngins vertebral disc is lost then we're more likely to damage it because it's stiffer it's more likely to get a prolapsed disc if you if you lift badly but nonetheless age aside you should be careful of your back right I think I think so the intervertebral discs those are the key ideas of the annulus fibrosus the ring around the outside retaining the squeegee nucleus pulposus in the middle which is full of proteoglycans and water which is why it's squeegee and the loads of cool collagen and stuff holdin all together and they're attached to adjacent vertebrae and they're a vascular so nutrients and oxygen and co2 stuff have to diffuse through the nucleus pulposus to the cells and back and the herniation you don't think about the other relevance and ask me around here spinal cord cord or a coiner spinal nerves alright alright okay [Music] you

Channel: Sam Webster

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Keywords: iv disc, iv disk, intervertebral disk, intervertebal disc, vertebra, spine, hernia, slipped disk, slipped disc, herniated, nucleus pulposus, anulus fibrosus, annulus fibrosus, prolapse, Sam Webster, back, Swansea, dontbeasalmon

Id: _s2JOhU0UJU

Length: 17min 53sec (1073 seconds)

Published: Tue Aug 07 2018