Type of collagen
More than 20 genetically distinct collagens exist in animal tissues. Collagen types I, II, III, V and XI self-assemble into D-periodic cross-striated fibrils. Here the D is approximately 67 nm and there is characteristic axial periodicity of collagen. These form the most abundant collagens in vertebrates.
Type I collagen is found throughout the body except in cartilaginous tissues. It is also synthesized in response to injury and in the fibrous nodules in fibrous diseases.
Type II collagen is found in cartilage, developing cornea and vitreous humour. These are formed from two or more collagens or co-polymers rather than a single type of collagen.
Type III collagen is found in the walls of arteries and other hollow organs and usually occurs in the same fibril with type I collagen.
Type V collagen and type XI collagen are minor components of tissue and occur as fibrils with type I and type II collagen respectively.
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