Cartilage Flashcards
What is the function of cartilage in general?
Specialized connective tissue Provides resilient support Resists compressive forces Capability to regain shape and size Smooth, cushioned surface for articulating bones
What are the cells in cartilage called?
Chondrocytes
Embedded within extensive extracellular matrix (cartilage matrix)
What are the three components of cartilage matrix?
- Fibers
- Ground substance
- Noncollagenous multiadhesive glycoproteins
What gives mechanical stability to the ground substance?
Fibers
What is the primary type of fiber found in the cartilage matrix?
Cartilage-specific collagens
Type II is predominant form
Collagen found at the periphery of the chondrocyte and facilitates the link between the chondrocyte and the cartilage matrix
Type VI Collagen
Stabilizes type II collagen by facilitating collagen fibril-proteoglycan interaction
Type IX
Associated with hypertrophic regions in cartilage where it organizes collagen fibrils into a 3D lattice
Type X
Regulates type II collage fibril size
Type XI
What is the predominant component of cartilage matrix?
The Ground Substance
Hydrated gel composed of water, ions and proteoglycans
What is the predominant proteoglycan monomer?
Aggrecan
What are multimolecular proteoglycan aggregates?
Aggrecan monomers bound to a central hyaluronate backbone
Have dense negative charge – keeps the aggregates expanded d/t repulsion, also water and sodium ions are attracted to hydrate the gel matrix
Small regulatory and structural proteins that influence interactions between chondrocytes and the ECM
Noncollagenous Multiadhesive Glycoproteins
What are some of the noncollagenous proteins?
Chondronectin
Tenascin
Anchorin CII
What are the multiadhesive glycoproteins clinically valuable markers for?
Cartilage turnover and degeneration
What is the function of chondrocytes?
They produce and secrete the components of cartilage matrix.
Also secrete enzymes that can degrade cartilage matrix.
Maintain the integrity of the cartilage matrix
What is the function of chondroclasts? What are they derived from?
Multinucleated cells that degrade calcified cartilage
Derived from monocytes and are similar to osteoclasts
What are some hormones that increase synthesis of cartilage?
Growth hormone
Thyroxin
Testosterone
What are some hormones that decrease synthesis of cartilage?
Cortisone
Hydrocortisone
Estradiol
What are cartilage elements often enclosed in?
A Perichondrium
What is the outer part of the perichondrium?
Fibrous connective tissue (primarily type I collagen) secreted by fibroblasts
Contains a capillary plexus, nerves and lymphatics
What is the inner part of the perichondrium?
Contains flattened chondrogenic cells that have the potential to become chondroblasts.
How are chondrocytes nourised?
Diffusion through the cartilage matrix
Do chondrocytes have a high or low metabolic rate?
High – despite being surrounded by an avascaular matrix
What are the three main types of cartilage?
Hyaline
Elastic
Fibrocartilage
What is the most common type of cartilage? How does it appaear?
Hyaline cartilage
Bluish-white, glassy appearance
What surrounds the chondrocyte acting as a biochemical buffer between the cell and the territorial matrix?
Pericellular matrix
Is a perichondrium present around hyaline cartilage elements?
Yes
What are two types of specialized hyaline cartilage?
Articular cartilage
Epiphyseal plates
What is the boundary betwen the deepest zone and three unmineralized zones above it in articular cartilage called?
Tidemark – it is a thick band of mineralized matrix
Does articular cartilage have a perichondrium?
No – enables it to remain smooth
What is the main component of elastic cartilage?
Elastin – makes it appear yellowish
Is a perichondrium present around elastic cartilage?
Yes
What does fibrocartilage have a lot of?
Type 1 collagen – makes it appear white and opaque
Does fibrocartilage have a perichondrium?
No
What is interstitial growth?
Growth from within
Chondrocytes separate as they divide because of new matrix production
Generally occurs in young cartilage
Important in epiphyseal cartilage for growth of long bones
What is appositional growth?
Growth from the surface
Inner layer of perichondrium has chondrogenic cells that have the potential to become chondroblasts (express SOX-9)
Chondroblasts secrete cartilage matrix and become enclosed within it.
Adds new cartilage to the surface of existing cartilage
What are some changes that occur in cartilage with aging?
Affects matrix organization, matrix mechanical properties and chondrocyte function
Disruption of collagen fibers at surface – rough articular surface
Progressive degeneration can leave deep pits/ulcers
Decrease in proteoglycan content –> cartilage softening (chondromalacia)
Chondrocyte death
What types of cartilage injury usually do not heal?
Injury that does not extend across the tidemark d/t lack of influx of chondrogenic cells, fibrin clot or growth factors
What types of degenerative changes can affect the intervertebral discs?
Decrease in water content of nucleus pulposis and proteoglycans that do not bind water increases
Size of aggrecan molecules decreases
Increase in collagen causes nucleus to become firm
Tears in annulus fibrosis
