Cartilage - Structure & Function Flashcards

Study Notes

Cartilage is a firm yet flexible connective tissue made up of chondrocytes in extracellular matrix (ECM).
Three main types of cartilage: hyaline, elastic, and fibrocartilage.

Provides shock absorption under mechanical stress.
Exhibits viscoelastic properties, offering flexibility while resisting deformation.
Serves as a lubricant for joints, minimizing friction and aiding movement.
Acts as a framework for bone development during embryonic and fetal stages.
Plays a key role in bone growth and development during adolescence.

Chondrocytes are the cells responsible for producing the cartilage matrix.
Their appearance varies based on location:
- Medullary chondrocytes have a rounded shape and may cluster in isogenous aggregates.
- Peripheral chondrocytes display an elliptical shape.
Chondrocytes reside in small cavities within the matrix called lacunae, surrounded by territorial matrix.

Composed of collagen fibrils, glycosaminoglycans (GAGs), proteoglycans, and chondronectin.
GAGs are hydrophilic polysaccharides with repeating disaccharide units.
The chemical composition of the ECM determines its gel-like properties.

Chondronectin is a linker glycoprotein that connects chondrocytes to the ECM.
Facilitates cell adhesion to collagen and GAGs through interaction with integrins.

A dense connective tissue layer encasing cartilage.
Contains fibroblasts that secrete type I collagen.
Supports the vascular and nervous supply to cartilage, promotes transition to ECM.
Histologically appears more eosinophilic compared to the inner cartilage matrix.

Cartilage lacks blood vessels, preventing calcification and hardening of its matrix.
Chondrocytes secrete anti-angiogenic factors to inhibit blood vessel formation.
Nutrient supply relies on diffusion from nearby vessels, limited by the absence of nerve and lymphatic networks.
This avascularity restricts the metabolic activity of chondrocytes.

Derived from mesenchyme through chondrogenesis, where mesenchymal cells condense and differentiate into chondroblasts.
Chondroblasts produce and deposit the cartilage matrix before maturing into chondrocytes.
In mature cartilage, chondrocytes remain quiescent, residing in the perichondrium.

Interstitial growth occurs via mitotic division of chondrocytes within the matrix, producing new lacunae.
Appositional growth happens along the perichondrium’s internal edge, differentiating cells into chondrocytes, allowing for growth at the periphery.
Interstitial growth is notable during early cartilage formation and less common in mature cartilage due to the dense matrix.

Hyaline Cartilage
- Most common type, located in costal cartilage, nose, respiratory tract, and articular surfaces of bones.
- Primarily composed of type II collagen and encased in perichondrium.
- Lacks perichondrium at articular surfaces.
Elastic Cartilage
- Similar to hyaline cartilage but contains a larger amount of elastic fibers, providing greater elasticity and pliability.
- Found in external ears, epiglottis, and parts of the larynx.
Fibrocartilage
- Intermediate between dense connective tissue and hyaline cartilage.
- Found in structures like intervertebral discs and symphysis pubis, providing strength and support.