Table 4.

Collagen subtypes, function, and anatomic location ^a

Molecular type	Key aspects	Constitution	Synthesizing cells	Function	Location (tissue)
I (Fibril forming)	Most abundant collagen type	2 α1(I) chains, 1 α2(I) chain	Fibroblasts, osteoblasts, odontoblasts, cementoblasts	Resists tension	Dermis, tendon, ligaments, capsules of organs, bone, dentin, cementum
II (Fibril forming)		3 α1(II) chains	Chondroblasts	Resists tension	Hyaline cartilage, elastic cartilage
III (Fibril forming)	Highly glycosylated, known as reticular fibers	3 α1(III) chains	Fibroblasts, reticular cells, smooth-muscle cells, hepatocytes	Forms structural framework of spleen, liver, lymph nodes, smooth muscle, adipose tissue	Lymphatic system, spleen, liver, cardiovascular system, lung, skin
IV (Network forming)		2 α1(IV) chains, 1 α2(IV) chain	Epithelial cells, muscle cells, Schwann cells	Forms meshwork of the lamina densa of the basal lamina to provide support and filtration	Basal lamina
V (Fibril forming)		2 α1(V) chains, 1 α2(V) chain	Fibroblasts, mesenchymal cells	Associated with type I collagen and with placental ground substance	Dermis, tendon, ligaments, capsules of organs, bone, cementum, placenta

^aData extracted from Gartner.³⁷