7/2 Bone/Cartilage

Cartilage: General Overview

• Definition (Clinically Oriented Anatomy)
  • “Resilient, semirigid form of connective tissue that forms parts of the skeleton where more flexibility is required.”
• Basic composition
  • Chondrocytes
  • Specialized cells that produce & maintain the extracellular matrix (ECM).
  • Extracellular Matrix (ECM)
  • Rich in collagen fibers.
  • Precise fiber makeup (type of collagen, ratio of elastin : collagen) differs by cartilage type.
• Fundamental properties
  • Generally avascular
  • Nutrients/O₂ reach chondrocytes only by diffusion → slow, limited healing.
  • Generally aneural (varies by region) → injuries may be painless until surrounding tissues involved.
  • Healing potential is therefore poor; injured regions often repair with mechanically inferior fibrous tissue.

Three Types of Cartilage (Comparison Framework)

• Key variables: collagen type, elastin : collagen ratio, permitted motion, mechanical role, anatomical locations.

1. Hyaline Cartilage (Articular Cartilage)

• Collagen content: predominately \text{Type II} collagen.
• Functions & significance
  • Covers ends of most bones in synovial joints.
  • Provides extremely low-friction surface → minimizes wear.
  • Assists joint lubrication in concert with synovial fluid.
  • Transfers/redistributes compressive forces to subchondral bone.
  • Forms the entire fetal skeleton (endochondral ossification template).
• Structural notes
  • ECM contains high water content (≈ 70-80 %), enabling resistance to compressive loading.
  • Lacks blood vessels and nerves →
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