Cartilage

Characteristics of cartilage

Avascular tissue(nutrients diffuse via ECM)

Mesoderm germ layer

main function is to resist compressive forces

Cartilage growth

abundant during ontogenesis but limited in adults

progenitor cells present in perichondrium

Appositional growth

growth on top of the existing matrix (stem cells)

Interstitial growth

growth within existing matrix (no stem cells)

Chondroprogenitor cells

unipotent stem cell located within perichondrium

Chondroblast

immature cell type located just deep to perischondrium

and activley produces components of ECM

Chondrocytes

mature cell that synthesizes and maintains ECM and are found typically in lacunae

Cartilage fibrous proteins

type 2 collagen always sometimes type 1 and elastic but not always

Cartilage ground substance

glycosaminoglycans that draw in high amounts of water to resist compressive forces

semi ridged support and allows diffusion of nutrients

Isogenic groups

newly divided cells

Lacunae

small cavities that hold chondrocytes

Territorial matrix

newly deposited matrix

Interterritorial matrix

older matrix

Hyaline cartilage cell types

Chondroblasts and chondrocytes

Hyaline cartilage matrix

Type 2 fibers and GAG aggregates

Hyaline Histologically

Hyaline cartilage growth

both appositional and interstitial

Perichondrium must be present for appositional growth

Hyaline cartilage function

resist compressive forces, provide a low-friction surface, and flexible support for respiratory system

Hyaline cartilage locations

costal cartilage, tracheal rings, nasal cartilage, articular surfaces

Articular cartilage

speicifc name for cartilage covering joints

no perichondrium

Articular cartilage nutrients

mechanical load forces synovial fluid to compress and thus deliver nutrients to the articular cartilage

Elastic cartilage cell types

chondroblasts and chondrocytes

Elastic cartilage extracellular matrix

type 2 and elastic fibers

Elastic cartilage histologically

Elastic cartilage growth

appositional and interstitial

all regions contain perichondrium

Elastic cartilage locations

Pinna of ear, external auditory meatus, auditory canel in nasopharynx, epiglottis, larynx

Fibrocartilage cell types

chondrocytes and fibroblasts

Fibrocartilage extracellular matrix

type 1 and 2 collagen but variable amounts dependent upon location

menisci of knee have little type 2 but intervertebral discs have equal amounts

high amounts of overall matrix

Fibrocartilage growth

interstitial only

Fibrocartilage function

resistance against compression, tearing and shearing forces, resists deformation, restricts movement where bones attaches

Fibrocartilage locations

intervertebral discs, mesnisci of knee, pubic symphysis, labrum of joint sockets, points of direct bone attachment, temporomandibular joint

TMJ exception

The TMJ is made up of fibrocartilage but has a perichondrium and thus has the benfits that comes along with having one

Cartilage in the head

ectoderm- derived neural crest cells

Cartilage repair limitations

limited by nutreints (perichondrium & synovial fluid

capacity to repair diminishes in early adulthood

Damaged tissue often results in fibrocartilaginous scar tissue

Hyaline cartilage aging

less mitotic activity

calcifies with age and may become bone leading to drying and cellular death

osteoclasts/chondroclasts clean up calcified tissue resulting in bone matrix deposition