cartilage

(kart′ĭ-lăj)

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[L. cartilago, gristle]
A specialized type of dense connective tissue consisting of cells embedded in a ground substance or matrix. The matrix is firm and compact; its proteoglycans can store considerably more sodium than plasma can, which in turn allows cartilage to store water, which in turn helps cartilage withstand pressure or impact. Cartilage is bluish-white or gray and is semiopaque; it has no nerve or blood supply of its own. The cells lie in cavities called lacunae. They may be single or in groups of two, three, or four.
Cartilage forms parts of joints in the adult skeleton, such as between vertebral bodies and on the articular surfaces of bones. It also occurs in the costal cartilages of the ribs, in the nasal septum, in the external ear and lining of the eustachian tube, in the wall of the larynx, and in the trachea and bronchi. It forms the major portion of the embryonic skeleton, providing a model in which most bones develop.

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