Lecture 7: Histology I: Cartilage Flashcards
bone and cartilage are specialized CT formed from ?
mesecnchyme derived from mesoderm
what does the lateral plate mesoderm form
green arrow
limb skeleton and sternum
what does the paraxial mesoderm form
light blue arrow
vertebrae, ribs and some of the skull
what does the neural crest form
parts of the skull
perichondrium cartilage is composed of how many layers and what are they
2 (outer fibrous and inner cellular)
what is the outer fibrous layer of cartilage composed of ?
- dense CT
- type I collagen
- fibroblasts
- vasculature
what it the inner cellular layer of cartilage composed of ?
chondrogenic cells = cartilage stem cells
- impt for appositional growth, maintenance and some repair
what cell type is arrow pointing to
chondrogenic cell = cartilage stem cell, a specialized fibrocyte producing cartilage ECM
characteristics of the chondrogenic cells
- narrow and spindle shaped
- ovoid nucleus w/ one or two nuclei
function of chondrocytes
secrete ECM
characteristics of Chondrocytes?
- ovoid to rounded shape
- large nucleus with prominent nucelolus
what cells are the blue arrows pointing to
chondrocytes
what type of cell is this?
what do the colored arrows each refer to
Chondrocyte
- blue = euchromatin
- pink = golgi
- yellow = rER
term for chondrocytes that are actively secreting ECM
chondroblasts
As ECM forms around a chondroblast, it forms a ______, a fluid filled space where the inactive chondrocyte resides
lacuna
what is the blue arrow pointing to ? yellow arrow? green arrow?
Blue = chondrocyte in lacuna
Yellow = empty lacuna
green = ECM
what is the composition of the extracellular matrix (ECM) of cartilage?
mostly water, supported by collagen fibers
Why is all cartilage avascular
- helps cartilage regulate fluid content to resist compression
where does cartilage receive its blood supply since it is avascular itself?
from nearby CT, diffusion from periphery
what are proteoglycan aggregates (PGAs)
very large aggregates of proteoglycans non-covalently bound to hylauronic acid
- they create internal pressure (turgor) that allows cartilage to resist compression without inhibiting its flexibility
what regions of matrix does each arrow point to
red = capsular matrix
- around chondrocytes
- many PGs
- very dark staining
blue = terrirorial matrix
- near chondrocytes
- type II fibrils, PGs
- dark staining
green = inter-territorial matrix
- away from chondrocytes
- few PGs
- pale staining
ECM components exist to help regulate water content in order to resist ______
compression
what cartilage type do these images depict
hyaline cartilage
- no visible fibers
- ECM stains pink or purple depending on the abundance of collagen
- NEVER has elastic or type I collagen fibers in its ECM
what cartilage type is this
elastic cartilage
- has elastic fibers in its ECM
What do these images depict
fibrocartilage
- type I collagen fibers
- no perichondrium
- chondrocytes of fibrocartilage are much larger and rounder than those in dense CT
physical difference b/w chondrocytes found in fibrocartilage vs in dense CT
- fibrocartilage chondrocytes are larger and rounder
- dense CT chondrocytes are flatter and elongated
what type of cartilage is this?
articular cartilage
what is cartilage comprised of
- large amount of functional ECM
- small amount of chondrocytes
what is articular cartilage and where is it found
a type of hyaline cartilage found on the surface of synovial joints
what type of cartilage is this
hyaline
- has isogenous group
- no fibers
what is this ?
subchondral bone
- bone supporting articular cartilage
- entirely covered by cartilage
- lacks chondrocytes
explain the steady state of cartilage
- maintained by chondrocytes
- steady state allows for normal anabolic processes
- synthesis of ECM components
- equilibrium w/ normal catabolic processes
- normal turnover of matrix molecules
how does injury to the cartilage matrix affect the steady state balance
injury causes chondrocytes to release cytokines that inhibit ECM secretion and enzymes that digest the ECM instead of factors to produce more matrix
this results in cartilage degeneration
fibrocartilage has no?
perichondrium
p
proteogylcans contain _________, which are molecules that attract water
Glycosaminoglycans (GAGs)
what binds proteogylcans to eachother, forming proteoglycan aggregates
hylauronic acid
ECM components of hyaline cartilage
- PGAs, MGPs, type II collagen
ECM components of elastic cartilage
- PGAs, MGPs, type II collagen AND elastic fibers
ECM components of fibrocartilage
- PGAs, MGPs, type II collagen AND type I collagen for resistance to tension
what is missing from articular cartilages that inhibits its ability to repair or scar
no perichondrium
