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 →
      -