okay we're gonna talk about skeletal cartilages in this video and the reason we talk about cartilage in the bone chapter is that cartilage is considered a skeletal tissue and not just because it supports joints but because most of your skeleton initially starts out is just cartilage so embryologically and fetal e it turns out that a lot of a lot of bones are cartilage and then they're eventually turned into bone and replace my bone and you find this in most bones of our body except for areas that require flexibility you know an example is to be your rib cage where the the cartilaginous portion anteriorly of your ribcage remains cartilage even after birth now skeletal cartilage is made of highly resistant molded cartilage tissue that consists primarily of water you don't find any blood vessels or nerves here so that it doesn't bleed nor is it painful and the way that cartilage gets this nutrient supply then is by surrounding perichondrium so perichondrium is a layer of dense connective tissue that surrounds cartilage and it basically helps to resist our expansion but also contains the blood vessels for nutrient delivery to the cartilage itself now cartilage is made of chondrocytes which are basically the you know mature cartilage cells that are encased in small cavities called lacunae and essentially these card chondrocytes help to maintain the jelly-like extracellular matrix of cartilage now there are three major types of cartilage we got highland elastic at fibrocartilage we talked about these back in chapter 4 on tissues but hyaline cartilage is notable because it provides support flexibility and resilience it's also the most abundant type that contains collagen fibers and you find this in joints at the ends of bones your ribs also the larger Airways like your larynx and trachea and your nasal cartilage is also made of hyaline cartilage think of this is you know strong but flexible now elastic cartilage is similar to Highland cartilage but contains lots of elastic fibers and therefore has more elastic characteristic to it now you find that elastic cartilage is located in the external ear and the epiglottis and the epiglottis is essentially a structure that prevents you from inhaling the food that you're swallowing and by being elastic it can recoil back to a resting shape that way you can breathe after swallowing now fibrocartilage is the toughest of these three types and it's tough because you got thick collagen fibers here that give it a high tensile strength so you find fiber cartilage in joints that need to resist a lot of compression force and a lot of you know potentially deforming damage so you find fiber cartilage in the menisci of your knee as well as the the intervertebral discs along your spine which makes sense because it can resist that compression force so this is a nice summary of the location of cartilage around the body in blue is all the locations of Highland so you see that hyaline cartilage is at the ends of your long bones and it serves as a nice protective cushion here you also find hyaline cartilage on the costal cartilage of your ribs because it's flexible and allows your ribcage to expand your nasal cartilage to support your nose and the cartilage of your Airways is also mostly a highland now fibrocartilage you only find in select areas you know like the intervertebral discs along your spine are little rings of fibrocartilage as well as the pubic symphysis which connects the two halves of your pelvis together it's also a little band of fibrocartilage now the function of the pubic symphysis is to allow a little bit of give or wiggle for the hips so that when you're walking the hips can actually kind of move against each other along this pubic symphysis there's also a hormone relaxin that's released during labor that causes the pubic symphysis to soften it allows this cartilage to be more stretchable that way the two halves of the pelvis can separate and it's easier for the the child to go through the birth canal now in green we have elastic cartilage here and elastic cartilage is what you find in the external ear that's why your ears can actually kind of pop back into position and you also find it in your epiglottis which helps to prevent you from aspirating or basically inhaling the food that you're swallowing and it can also pop back into position which allows you to you know have adequate airflow after swallowing now in terms of growth of cartilage there's two major forms we've got a positional growth in interstitial growth appositional growth refers to cartilage formation in the perichondrium that way new matrix new cartilage is laid down at the surface of the cartilage like the newer portions are on the outer edge of that cartilage because it occurs in the perichondrium so an example of a positional growth in the environment could be like as pearls grow you know pearls which are essentially layers of minerals that that are deposited around a piece of dirt or some kind of imperfection inside of a clam shell new layers of mineralized pearl material or laid down on the outside just like with a positional growth new layers of matrix are laid down on the outside of that cartilage now this differs from interstitial growth which is still a lot more like tree growth where new cartilage actually occurs from deep within the cartilage so the older cartilage is located more towards the periphery or outer edge of the cartilage and then the newer material is actually found deep within the cartilage itself kind of like rings on a tree where the new tree growth is actually in the very center and the old tree growth is out towards the edge now calcification of cartilage can occur during normal bone growth and in youth but can also occur in an old age wood cartilage calcify as it can turn into bone and as we age you know cartilage can also be calcified due to injury or trauma and we call this hardened cartilage but it's not the same as bone because cartilage is a vascular bone as vascular but College can calcify into something that's like bone but it's not truly considered thumb