Lecture 8: Microanatomy of Cartilage Flashcards
embyronic origin of cartilage (and bone)
mesenchyme from mesoderm
chondrogenic cells
cartilage stem cells
articular cartilage definition
hyaline cartilage with NO perichondrium
what 2 types of cartilage have perichondrium
elastic
hyaline
perichondrium definition
dense CT surrounding elastic and hyaline cartilage
what 2 types of cartilage are not surrounded by perichondrium
fibrocartilage
articular cartilage
2 layers of perichondrium
outer fibrous layer
inner cellular layer
components/features of outer fibrous layer: perichondrium
type 1 collagen
dense CT
fibroblasts
VASCULATURE
when no perichondrium is present, where are nutrients received from
synovial fluid
component of inner cellular layer: perichondrium
chondrogenic cells
Chondrocyte definition/function
Specialized fibrocyte producing cartilage ECM
Quiescent
Chondrocytes vs chondroblasts
Chondroblasts are ACTIVELY secreting ECM
How is lacuna formed
ECM forms around chondroblast
Lacuna definition
Fluid filled space where quiescent chondrocyte resides
2 ways cartilage grows
Appositional growth
Interstitial growth
Appositional growth process
Chondrogenic cells in perichondrium undergo mitosis and differentiate into chondrocytes/chondroblasts that secrete ECM
New cells and ECM added to edge of pre existing tissue (on outer surface)
Interstitial growth process/features
Chondrocytes undergo mitosis to produce daughter cells that stay close to each other and form isogenous groups
Isogenous groups produce ECM and get pushed apart
New cells and ECM added within tissue
Growth occurs in any direction
Isogenous group definition
Collection of Chondrocyte daughter cells that remain close together
In what kind of cartilage growth process can growth occur in any direction
Interstitial
Extracellular matrix definition
Mostly water
Supported by collagen fibers
Secreted by chondroblasts
Is cartilage vascular
No
How does cartilage receive blood supply
Nearby CT = perichondrium, joint capsule (synovia)
What helps cartilage regulate fluid content and resist compression
Avascularity
ECM
Proteoglycans definition
Protein bound to glycosaminoglycans
Glycosaminoglycans function
Attract water
Proteoglycan aggregates: definition, function, location (general)
Aggregates of proteoglycans bound to hyaluronic acid in ECM
In cartilage
Create internal pressure that allows cartilage to resist compression without inhibiting flexibility —> TURGOR
Main structural components of cartilage (4)
Mostly water
Cells
Collagens
Glycosaminoglycans and proteoglycans
3 regions of ECM
Capsular matrix
Territorial matrix
Inter territorial matrix
Capsular matrix of ECM: amount of proteoglycans, stain color, relation to chondrocytes
Around/surround chondrocytes
Many proteoglycans
Stain very dark purple
Territorial matrix of ECM: amount of PG’s, stain color, relation to chondrocytes
Near chondrocytes
Type II fibrils, PGs
Dark staining (but not as dark as capsular matrix)
Inter territorial matrix of ECM: amount of PG’s, stain color, relation to chondrocytes
Few PG’s
Away from chondrocytes
Pale staining
What stain must be used to indefinite elastic fibers
Verhoeff’s or orcein
PG’s vs collagen in cartilage stain what color
Purple for PGs
Pink for collagen
Elastic cartilage requires added
Flexibility
Fibrocartilage must be able to
Resist tension
What kind of cartilage is found in intervertebral disc
Fibrocartilage
What kind of cartilage is found inside the trachea
Hyaline
What kind of fibers are never present in hyaline ECM
Type 1 collagen
Elastic
articular cartilage definition
type of hyaline cartilage found on surfaces of synovial joints
articular cartilage lacks (3)
perichondrium
type 1 collagen
elastic fibers
subchondral bone
bone supporting articular cartilage
covered completely in cartilage
balanced steady state of chondrocytes in cartilage
synthesis/anabolic of ECM components in equilibrium with normal turnover/catabolism of matrix molecules
damage to cartilage matrix: how it affects balance
chondrocytes release more cytokines that inhibit ECM secretion and enzymes that digest ECM vs factors that produce more matrix –> cartilage degeneration
can articular cartilage repair/scar… why or why not
no
no perichondrium
repair of damaged cartilage tissue can be initiated where
perichondrium
