Cartilage Lecture by Dr. Noor Alaa M.B.Ch.B

Cartilage Overview

• Cartilage is a tough, resilient type of connective tissue that supports soft tissues, particularly in the respiratory tract, and provides cushioned, low-friction surfaces in joints.

Cartilage Composition

• Cartilage is composed mainly of chondrocytes and chondroblasts that synthesize an extensive extracellular matrix.
• Extracellular matrix includes collagen (notably type II), proteoglycans (notably aggrecan), and a high water content.

Cartilage Characteristics

• Cartilage is nonvascular, but surrounded by vascular connective tissue perichondrium.
• Nutrients enter and metabolites leave cartilage through diffusion through the matrix.

Types of Cartilage

Hyaline Cartilage

• Has a homogeneous and glassy extracellular matrix rich in type II collagen and aggrecan complexes with bound water.
• Chondrocytes occur singly or in small, mitotically derived isogenous groups.
• Perichondrium is dense connective tissue containing chondroblasts, fibroblasts, and blood vessels.

Elastic Cartilage

• Has a matrix that includes abundant elastic fibers, increasing tissue flexibility.
• Provides flexible support for the external ear, middle ear, and larynx structures.
• Always surrounded by perichondrium.

Fibrocartilage

• Contains varying combinations of hyaline cartilage and dense connective tissue.
• Histologically, it consists of small chondrocytes in a hyaline matrix, layered with bundled type I collagen and scattered fibroblasts.
• Provides very tough, strong support at tendon insertions, intervertebral discs, and certain joints.

Cartilage Formation, Growth, and Repair

• All forms of cartilage form from embryonic mesenchyme.
• Cartilaginous structures grow by mitosis of existing chondroblasts (interstitial growth) or formation of new chondroblasts peripherally from progenitor cells in the perichondrium.