okay so in this video we're going to look at the the types of fibrous joints so in the last video we talked about how there are uh three uh structural classifications of joints we had fibrous cartilaginous and synovial and all the fibrous joints are made of dense fibrous connective tissue uh now these types of joints don't have a cavity instead what happens is these bones are just tightly linked by this dense fibrous connective tissue and if you guys remember this is a type of um connective tissue proper that's vascularized but the reason why it's dense is that there's a lot of fibers here and they're so densely packed that it makes this type of tissue strong and because this type of tissue is so strong typically these fibers joints are immovable or synarthrotic however that does depend on the length of these fibers so if you have longer fibers the joint is going to be slightly movable and if they're shorter fibers it's it's going to be immovable or synarthrotic so there's three types of fibrous joints we have sutes cmosis and gomoses so the SU are these rigid interlocking joints of the skull and they actually allow for some growth during youth now because these fibers that hold the cranial bones together are so short um it allows for the skull to kind of expand slowly but also limits the movability of these cranial bones and uh what's interesting too is that as we get older these sutures aify and fuse and they're completely immovable at this point and so at that at the point where there's not really many fibers left and the cranial bones are fused together we call this a sinos osis so if you look at the structure of a sutal joint just very closely remember it's a type of fibrous joint and if you look here between the cranial bones let's say at the juncture of like the sphenoid and the temporal bone or parial bone what you find then is that these are two separate cranial bones and at the place where these bones meet you find that they're very intimately and tightly linked by this type of fibrous joint which is a suture now it's a dense fibrous tissue and there's so many of these short fibers that these bones are going to be held together very strongly and very stable now what's interesting is that as we get older these types of fibrous joints start to disappear and instead what we have is a synostosis where're just bone that's fused together um and that's one of the ways you actually determine the age of of someone's skull so cmosis is actually where you have bones connected by ligaments so they're longer fibers and remember technically a ligament is where you have uh basically dense regular connective tissue that connects bone to bone and they're longer fibers so these ligaments can be SL L movable now the fiber length can vary and movement can vary but shorter fibers are going to offer little to no movement so like an example this would be like the uh tibio fibular joint there's very little movement there um but the longer fibers you know areas where you have like long fibers let's say in the inner oous membrane like between your radius and your olna or between the tibia and fibula uh this inter oous membrane which connects the two bones uh longitudinally uh or transversally rather uh they're longer fibers so they actually allow for a slight degree of movement of those bones so for instance when you when you rotate your forearm like anterior and posteriorly uh what happens is the radius actually rotates around the olna and there's some degree of movability in this interner oous membrane so if you look at an example of a syndesmosis uh we find that is these connective tissue fibers here that would connect things like your tibia and fibula together now technically this is a ligament because it connects bone to bone and therefore is also a cend is because these fibers are a little shorter it offers very little movement so this is going to be somewhere between a synarthrosis and an amphiarthrosis in terms of movability uh but you would also find interus membrane between these bones so if you if it were in this picture it's not but between the fibula and tibia here you can find a membrane of of connective tissue fibers as well and that actually is going to be slightly movable if these bones rotate like when your when your whole L when your whole leg rotates now the gomphosis is the last type of F joint we'll talk about here and these gum foses are all pegan socket joints and they're basically where teeth fit into the alveolar sockets so uh technically your teeth aren't bone but they're held in place by a fibrous joint and uh this fibrous connection is what we call the periodontal ligament or the goosal fibers and they hold the tooth in the socket in fact I like to talk about how you know if you think about if you ever had a tooth removed or when you're a child and you've lost your teeth how that when the teeth when the tooth coming out you can feel the fibers kind of ripping away from the The goosal Joint so if you look at the structure of gomphosis you know here's the tooth itself uh tooth is actually more similar to uh the nervous system and skin than bone and so technically teeth are not bone they're structured like bone because they're hardened but they come from ectoderm so they're more similar to Bone I'm sorry they're more similar to their nervous system and skin now this is where the gum line meets the tooth and if you look here at the root of the tooth is actually held to the Bone itself where whether it's the mandible or Maxa by these fibers right here and so these are the goosal fibers and we also have a periodontal ligament here that would hold hold this tooth in place now because this is immovable we would also call this a synarthrosis because this typically shouldn't be moving a whole lot