Collagen is the most abundant protein of vertebrates, and occurs in virtually every tissue. Collagen proteins building collagen fibrils are the main components of the supporting tissue of connective tissue, bones, cartilage, teeth and extracellular matrices of skin and blood vessels.
The complex composition of connective tissue has to be taken into account when tissues need to be dissociated in research or clinical situations, such as the preparation of suspensions of viable cells for metabolic studies, the isolation of pancreatic islets in diabetes research and the clinical treatment of necrotic tissue.