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