Histology Cartilage

Characteristics of Cartilage

Extensive matrix enriched with GAGs, multiadhesive glycoproteins, and proteoglycans

Macromolecules interact with collagen II fibrils and elastic fibers (resist tension, bear weight)

Chondrocytes in lacunae produce ECM

Avascular, no innervation

Usually surrounded by perichondrium

Hyaline Cartilage

Most common Cartilage

Appears glassy

Locations in Adult: Articular surfaces of joints, respiratory passageways, costal cartilages, epiphyseal plate

Functions: Structural support in airways, resists compression, cushioning and low-friction, makes up fetal skeleton and endochondral bone formation

Ground Substance of Hyaline Cartilage

Capsular and Territorial Matrix - Rich in GAGs, poor in collagen II, metachromasia

Interterritorial Matrix - matrix between lacunae, less basophilic

Cartilage Cells

Chondrogenic Cells - mesenchymal cells

Chondroblasts - found in inner cellular layer of perichondrium

Chondrocytes - cells of cartilage that are surrounded by matrix and located in lacunae. Prominent golgi in active cells, smaller in inactive.

Chondrogenesis of Hyaline Cartilage

1. Embryonic mesenchyme

2. Mesenchymal cells rounded and condensed - chondroblasts

3. Chondroblasts secrete matrix which separate cells - chondrocytes

4. Peripheral mesenchyme condenses around cartilage to form perichondrium

Chondrogenesis is regulated by many molecules and influenced by biomechanical forces that regulate shape and aging of cartilage.

Interstitial Growth

Mitotic division of pre-existing chondrocytes (divide in lacunae)

Appositional Growth

Results from differentiation of cells within the perichondrium (think bone formation)

Perichondrium

Dense, regular CT

Inner cellular layer is the source of chondroblasts

Outer fibrous layer composed of Collagen I and fibroblasts

Lacking in articular cartilage

Hyaline Cartilage Repair

Limited ability to repair (avascular, immobility of chondrocytes)

Blood vessels develop at sight of the healing wound that stimulate bone rather than cartilage repair.

If perichondrium is present, repair mostly involves production of dense CT (scar)

Elastic Cartilage

Similar to hyaline cartilage, but elastic fibers form within matrix

Similar perichondrium and growth as hyaline cartilage

Chondrocytes are larger and more abundant than hyaline cartilage

Function - flexible support

Location: auricle of ear, external auditory canal, eustachian tube, epiglottis (ear and throat)

Fibrocartilage

Intermediate features between dense CT and hyaline cartilage

Similar to hyaline, but contains collagen I fibers

Chondrocytes are widely separated and arranged into isogenous groups (pea pod)

No perichondrium

Location: intervertebral disks, pubic symphysis, knee meniscus

Function: provide resistance to both compression and shearing