Connective tissue in parts of the human skeleton. A network of collagen fibres in a firm, gelatinous base, it contains no blood vessels or nerves. Different types of cartilage are found at the ends of some bones and in nasal and respiratory structures; in the spinal disks; and in the ear and epiglottis (back of the throat). Most of the skeleton of an embryo is made of cartilage, which is later replaced by bone.
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Cartilage is a type of dense connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix composed of collagen fibers, abundant ground substance rich in proteoglycan, and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in the relative amounts of these three main components.
Cartilage is found in many areas in the body including the articular surface of the bones, the rib cage, the ear, the nose, the bronchial tubes and the intervertebral discs. Its mechanical properties are intermediate between bone and dense connective tissue like tendon.
Unlike other connective tissues, cartilage does not contain blood vessels. The chondrocytes are fed by diffusion, helped by the pumping action generated by compression of the articular cartilage or flexion of the elastic cartilage. Thus, compared to other connective tissues, cartilage grows and repairs more slowly.
Tumors made up of cartilage tissue, either benign or malignant, can occur. They usually appear in bone, rarely in pre-existing cartilage. The benign tumors are called chondroma, the malignant ones chondrosarcoma. Tumors arising from other tissues may also produce a cartilage-like matrix, the best known being pleomorphic adenoma of the salivary glands.
The matrix of cartilage acts as a barrier, preventing the entry of lymphocytes or diffusion of immunoglobulins. This property allows for the transplantation of cartilage from one individual to another without fear of tissue rejection.
- Once damaged, cartilage has limited repair capabilities. Because chondrocytes are bound in lacunae, they cannot migrate to damaged areas. Also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is usually replaced by fibrocartilage scar tissue. Over the last years, surgeons and scientist have elaborated a series of cartilage repair procedures that help to postpone the need for joint replacement..
Cartilage degradation is fully reversible in the presence of aggrecanase but not matrix metalloproteinase activity.(Research article)
May 30, 2008; Authors: Morten A Karsdal (corresponding author) ; Suzi H Madsen ; Claus Christiansen ; Kim Henriksen ; Amanda J...
Cartilage-selective genes identified in genome-scale analysis of non-cartilage and cartilage gene expression.(Research article)(Clinical report)
Jun 12, 2007; Authors: Vincent A Funari ; Allen Day ; Deborah Krakow [1,2,3]; Zachary A Cohn ; Zugen Chen ; Stanley F Nelson [2,4];...