Cartilage is a supporting tissue that is present at various sites in the body. The ears, the nose and the airtube consist for an impotant part of cartilage. Also ribs, meniscus and intevertebral discs in the back are cartilage, and cartilage covers the end of bones in a joint.

 

Three different types of cartilage exist:

1. Hyaline Cartilage (e.g. present in joints, nasal septum, airtube)

2. Elastic Cartilage (e.g. ear, part of the nose and airtube)

3. Fibrous Cartilage (e.g. meniscus)

 

The different types have slightly different properties that make each type the most appropriate to fullfill its function at that particular site.

 

Cartilage basically consists of two components: water and a framework of structural macromolecules (matrix) that give the tissue its form and function. The matrix is highly organized and composed of collagens, proteoglycans and noncollagenous proteins.

 

The interaction of water and the macromolecular framework give the tissue its mechanical properties and thus its function. Up to 65% - 80% of the wet weight of cartilage consists of water, the rest is matrix, mainly collagens and proteoglycans. In case of elastic cartilage, elastic fibers are present that make the cartilage more flexible. Proteoglycan and noncollagenous proteins bind to the collagenous meshwork and water, attracted by negatively charged glycosaminoglycans, fills the molecular framework.

 

Embedded in this tight matrix are the cells, called chondrocytes, that take care of maintainance of the matrix. The volume of cells is rather small; In adult human cartilage for example, cells make up about 1-2% of the tissue volume. Chondrocytes are of mesenchymal origin and are responsible for extracellular matrix production. Cartilage is an avascular, aneural and alymphatic tissue. Nutrition of chondrocytes occurs by diffusion.

 

Cartilage is a very organized structure. This makes it particularly difficult to restore or duplicate once it is damaged or lost. Injury to any part of this complex system can disrupt the functional properties of cartilage. In case articular cartilage is involved, this may lead to further joint degeneration; In case cartilage of the airway is involved, this may lead to breathing problems. And in case of cartilage of the ear or nose, cosmetic problems might be the result.