lecture 4: cartilage Flashcards
complex of cells and extracellular matrix that provides supporting and connecting framework for all other tissues of the body
connective tissue
ECM provides
support
a way for cells to interact
ECM can be divided into two groups
Fibers
- provides structural support and tensile strength
ground substance
- part protein, part sugar
ECM fibers can be broken into 3 groups
- collagenous or fibrillar (30 types; fibril forming and non) (pink rope like structures)
- reticular (non-fibril- forming) (criss cross network)
- elastic (elastin) (walls of arteries, allow stretch)
describe ECM ground substance
Part sugar/ part protein
glycosaminoglycans/proteoglycan
- long negative charged chains (sulfate groups and carboxyl groups make it negative)
structural glycoproteins
- branched
- (fibronectin, laminin, vitronectin, tenascin, thrombospondin, entactin, ect)
what charge does glycosaminoglycans/proteoglycan have and why?
sulfate groups and carboxyl groups (make it negative)
Cartilage cells
chondrocytes
chondrocytes secrete ___
the extra cellular matrix
ground substance (little specs) usually closer to the cell
fiber component usually farther away from cell
what is this
fibril
components of ECM
fibril is made of
a bunch of collagen molecule
eosinophilic-will stain pink
placed like “bricks” have little openings (hole zones) between each other that make fibril have stripped appearance
(individual, head to tail quarter staggered collagen molecules)
fibrils will randomly criss cross each other this is called
cross striated collagen fibrils
collagen molecule is made of
3 polypeptide chains that wind around each other
- type II collagen
- trimeric
- rope like, rigid
+ charged (many basic amino acids’s (lysine and histidine))
what makes collagen molecule positive charge
has a lot of positively charged amino acids
lysine and histidine
eosin is a ___ dye
acidic dye
negative charge
will stain basic (+) acidophilic structures pink
hematoxylin is a ___ dye
basic
positive charge
will stain acidic(-) or basophilic structures blue/purple
collagen is ___ charged therefore it will stain with ___ and be ___
positive charged
eosin
pink
make up of ground substance
supramolecular aggregate of sulfated proteoglycans (negative charge)
back bone of hyaluronic acid (GAG) glycosaminoglycans
cross attached with proteoglycans (core protein)
each protein have more GAG cross attached to them
attached to each other by link proteins
back bone of ground substance
hyaluronic acid (GAG)
glycosaminoglycans (chain of repeating sugar heterodimers)
what is the name of the GAG molecules that attach to the core proteins of ground substance
chondroitin sulfate
keratan sulfate
(contains sulfate groups, high negative charge)
what is special about
chondroitin sulfate
keratan sulfate
and where are they found
contain sulfate groups
high negative charge
cross linked to core proteins of ground substance
what does the negative charge of the GAG chains do
spread out for each other and GAG on other core proteins
- hydrophilic- bind to water/ very hydrated- jello like
- basophilic ( will bind to hematoxylin- will stain purple)
-metachromatic- shift in color of the stain
what does GAG proteins being hydrophilic do?
makes them bind to a bunch of water
gel-like, jello like
very hydrated
most common type of cartilage
hyaline
younger cartilage cells live on the ___ of tissue
outside
chondroblasts
older, more mature cartilage cells live ___
deeper within tissue
surrounded by ECM- ground substance and type II fibrils
Chondrocytes
how does cartilage get nutrients
perichondrium
two layer membrane on surface of cartilage that contains
- outer membrane dense irregular connective tissue and vasculature
- inner membrane has progenitor cells for cartilage
perichondrium layers
- outer membrane dense irregular connective tissue and vasculature
- inner membrane has progenitor cells for cartilage
what enables cartilage to be compressed
sulfated proteoglycans
when compressed they will let go of the water and get closer to each other, compress
when compression stops, they will rebind to water and expand away from each other
proteoglycans can bind to water but will also bind to ___
growth factors and cytokines needed for cartilage development
calcium- prevents cartilage from mineralization (prevents from binding to phosphate which starts mineralization)
What does calcium binding to proteoglycan of ground substance of cartilage do?
prevents cartilage from mineralization (prevents from binding to phosphate which starts mineralization)
formation of cartilage
chondrogenesis
steps of chrondrogenesis
mesenchymal condensations (progenitor cells)
chondroblasts
chondrocytes
isogenic groups
mesenchymal cells in chondrogenesis
star shaped cells, migrate as a sheet until they get to where cartilage is to be formed and get pushed together and form into chondroblasts
chondroblasts
made from mesenchymal cells pushed together
start to secrete ECM, when cells make so much ECM it pushes them away from each other they are then referred to as mature chondrocytes
chondrocytes
surrounded by ECM
will divide but can’t move away from each other will form isogenic groups
the matrix directly outside a isogenic group
isogenic group- chondrocyte and its daughter cells
territorial matrix- usually has more sulfated proteoglycans
(stain purple- more negative)
the matrix father away form isogenic groups
inter territorial matrix
has less sulfated proteoglycans
has more fiber components
stains (pink- more positive)
home where chondrocytes live in the EMC
lacunae
where is the perichondrium
describe what is happening
hyaline cartilage surrounded
2 layer perichondrium
dense irregular connective tissue with vessels
and inner layer with progenitor cells
young chondroblasts secreting ECM forming into chondrocytes
chondrocytes dividing to turn into isogenic groups
two ways cartilage can grow
apositional
interstitial
describe apositional growth of cartilage
outside/border of cartilage
perichondrium
chondroprogenitors turning into chondroblasts which secrete ECM and turn into chondrocytes
where does apositional growth of cartilage happen
perichondrium (2 layer border of cartilage) happens in inner layer
describe interstitial growth of cartilage
chondrocytes dividing into isogenous groups
happens on inside of cartilage
because cartilage can ___ it can grow very happidly
grown two ways: apositional and interstitial
three types of cartilage
hyaline
elastic
fribrocartilage
describe hyaline cartilage
type II collagen
Function: structural support, rapid growth, withstand compression
Locations: fetal skeleton, respiratory passages (laryngeal, tracheal, bronchial cartilages), cushioning of joints
describe elastic cartilage
Type II collagen and elastin
Function: flexible support, ability to withstand deformation
Location: external ear, auditory tubes, epiglottis, larynx cartilage
describe fibrocartilage
type I and Type II collagen
Function: attachment to bone, provides restricted mobility under great mechanical stress
Location: annulus fibrosus of intervertebral disks, pubic symphysis, bone-ligament junctions (always found in association with dense connective tissue)
in fibrocartilage isogenous groups are found in ___
rows
endochondral ossification
how bone is formed from cartilage precursor
primary center of ossification
bony collar forms on diaphysis (shaft)
this triggers maturation of cartilage which ends in cartilage hypertrophy
this allows vasculature to enter cartilage which brings cells that eat cartilage and form bone
will form bony spicules and marrow cavity
This processes is repeated at ends of bone (secondary center of ossification)
area in between centers of ossification are the cartilaginous growth plates
When bone fully developed growth plate degrades and primary and secondary ossification centers fuse
1st step of endochondral ossification
bony collar forms around shaft of bone
perichondrium becomes periosteum
triggers
zone of proliferation
zone of hypertrophy
1st step of endochondral ossification perichondrium becomes ___
periosteum
zones of endochondral ossification
zone of proliferation
zone of hypertrophy
zone of erosion
zone of ossification
Zone of hypertrophy is able to be __
invaded by vasculature which brings in mesenchymal progenitor cells and chodroclasts and osteoclasts
chondroclasts do what___
(eat) break down cartilage
(zone of erosion)
zone of ossification
mesenchymal progenitor cells transform into osteoblasts
where bone is being formed on top of the hypertrophic cartilage remnants
what is I
zone of resting
what is II
zone of proliferation
cartilage cells rapidly divide and form rows
what is III
zone of hypertrophy
cartilage cells grow in size, get really big
cartilage cells form different type of ECM
What is IV
Zone of erosion
chondroclasts eat cartilage
came from outside bone when vessels invaded
What is V
zone of ossification
mesenchymal cells transform into osteoblasts which make bones on the hypertrophic cartilage matrix backbone
form trabecular bone
bone marrow cavity forms
where does cartilage remain when bone is fully grown
articular cap
(end of bone)
does not have perichondrium- can not rebuild itself- osteoarthritis
structure of hyaline cartilage
avascular
hydrated sponge concept
molecular seive concept
when cartilage is replaced by bone inside of long bones it is called
trabecular bone (spongy bone)
in collagen fibril the area where collagen molecules connect
hole zones
collagen molecules are “staggered”
gives stripped appearance
Type II collagen
trimeric molecule
laterally aggregates into fibrils
fibrils criss cross randomly
slightly basic (positive), eosinophilic (pink)
provides rigid structural support
supramolecular PG/GAG aggregates
hyaluronic acid backbone
mainly chondroitin/keratan sulfate side chains
highly negative, basophilic (purple stain)
hydrophilic- spongy, gel like
metachromatic stain- changes color of stain
outer layer of perichondrium is
gense irregular CT
has vessels
fibrocartilage forms in___
rings
isogenous groups are in rows
