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

  • Cells of cartilage, chondrocytes, make up a small percentage of the tissue’s mass, which is mainly a flexible mass of extracellular matrix (ECM).

  • Chondrocytes are embedded within lacunae surrounded by the ECM.

  • Cartilage ECM typically includes collagen as well as abundant proteoglycans, notably aggrecan, which bind a large amount of water.

  • Cartilage always lacks blood vessels, lymphatics, and nerves, but it is usually surrounded by a dense connective tissue perichondrium that is vascularized.

  • There are three major forms of cartilage: (1) hyaline cartilage, (2) elastic cartilage, and (3) fibrocartilage.

Hyaline Cartilage
  • The ECM of hyaline cartilage is homogenous and glassy, rich in fibrils of type II collagen and aggrecan complexes with bound water.

  • The ECM has less collagen and more proteoglycan immediately around the lacunae, producing slight staining differences in this territorial matrix.

  • Chondrocytes occur singly or in small, mitotically derived isogenous groups.

  • Perichondrium is usually present, but not at the hyaline cartilage of articular surfaces or the epiphyses of growing long bones.

Elastic Cartilage
  • Elastic cartilage generally resembles hyaline cartilage in its chondrocytes and major ECM components, but its matrix includes abundant elastic fibers, visible with special stains, which increase the tissue’s flexibility.

  • Elastic cartilage provides flexible support for the external ear as well as certain structures of the middle ear and larynx; it is always surrounded by perichondrium.

  • Fibrocartilage contains varying combinations of hyaline cartilage in small amounts of dense connective tissue.

  • Histologically, it consists of small chondrocytes in a hyaline matrix, usually layered with larger areas of bundled type I collagen with scattered fibroblasts.

  • Fibrocartilage provides very tough, strong support at tendon insertions and in intervertebral discs and certain other joints.

Cartilage Formation, Growth, & Repair
  • All forms of cartilage form from embryonic mesenchyme.

  • Cartilaginous structures grow by mitosis of existing chondroblasts in lacunae (interstitial growth) or formation of new chondroblasts peripherally from progenitor cells in the perichondrium (appositional growth).

  • Repair or replacement of injured cartilage is very slow and ineffective, due in part to the tissue’s avascularity and low metabolic rate.


Cartilage is a tough, durable form of supporting connective tissue, characterized by an extracellular matrix (ECM) with high concentrations of GAGs and proteoglycans, interacting with collagen and elastic fibers. Structural features of its matrix make cartilage ideal for a variety of mechanical and protective roles within the adult skeleton and elsewhere (Figure 7–1).


Distribution of cartilage in adults.

(a) There are three types of adult cartilage distributed in many areas of the skeleton, particularly in joints and where pliable support ...

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