Lecture 7- Histology of Cartilage Flashcards
Bone and cartilage are specialized ____
Connective tissue
What do bone and cartilage form from and where are they derived
From from mesenchyme and derived from the mesoderm
What does the lateral plate mesoderm make
Limbs, sternum
What does the paraxial mesoderm make
Vertebrae, ribs, some of skull
What does neural crest make
Some of skull
What os the perichondrium
Dense connective tissue surrounding elastic and hyaline cartilages, except articular cartilage
What two types of cartilage don’t have a periochondrium
Fibrocartilage and articular cartilage
What is the outer fibrous layer of the perichondrium made of
Dense CT, type I collagen, fibroblasts, vasculature
What is the inner cellular layer of perichondrium made of
Chondrogenic cells- cartilage stem cells, important for a-positional growth, maintenance and some repair
What supplies nutrients to hyaline and elastic cartilage
Perichondrium
What supplies nutrients to Fibrocartilage and articular cartilage
Synovial fluid
What is a chondrocyte
Specialized fibrocyte producing cartilage ECM
What is a chondrogenic cell
Cartilage stem cell that forms chondrocytes
What are chondrocytes called when they are actively secreting ECM
Chondroblasts
What is a lacuna
Fluid filled space where a quiescent chondrocyte resides
What is appositional growth
Chondrogenic cells in the periochondrium undergo mitosis and differentiation into chondrocytes that secrete ECM, new cells are added to the edge of pre-existing tissue towards the perichondrium
What is interstitial growth
Chondrocytes under mitosis deep in cartilage and produce daughter cells that form isogenous groups and when they secrete ECM they separate and can grow in any direction
What are isogenous groups
Chondrocyte daughter cells that remain close together
What is ECM made of
Mostly water and collagen fibers
Is cartilage avascular or vascular
Avascular
How does cartilage regulate fluid and resist compression
Avascularity and ECM components
Cartilage is abundant with proteoglycans which bind to hylauronic acid. PG’s contain glucosaminoglycans that attract water
PGA’s create an internal pressure (turgor) that allows cartilage to resist compression without inhibiting flexibility
What is the central matrix
Area surrounding chondrocytes, many PG’s, dark staining
What is the territorial matrix
Area near chondrocytes, type II fibrils, PG’s, dark staining
What is the inter-territorial matrix
Away from chondrocytes, few PG’s, pale staining
What does elastic cartilage require
Elastin for added flexibility
What does Fibrocartilage require
Type I collagen to resistance tension
Hyaline cartilage histology
Contains isogenous groups and perichondrium, no visible fibers, ECM stains pink (collagen) or purple (PG’s), never has elastic or type I collagen
Elastic cartilage histology
Elastic fibers in ECM, isogenous groups, perichondrium
Fibrocartilage histology
Type I collagen that appears as broad pink bands, no perichondrium, chondrocytes align with type I collagen
Articular cartilage histology
Type of hyaline cartilage, but no perichondrium, still have isogenous groups
Found on surfaces of synovial joints so contain an underlying subchondral bone that should be entirely covered by cartilage, bone stains dark pink and lacks chondrocytes
What happens during a cartilage injury
Normally chondrocytes maintain a balance where their secretion of ECM aligns with their turnover of ECM but during injury chondrocytes release more cytokines that inhibit ECM secretion and enzymes that digest ECM opposed to producing factors that make more matrix resulting in cartilage degeneration
Where can some repair of cartilage be initiated
Perichondrium, but can lead to build up of scar tissue
What is the result of damage to articular cartilage
Articular cartilage lacks a perichondrium so there is no repair or scaring- leads to degenerative joint disease
