TY - CHAP M1 - Book, Section TI - Alterations of Collagen and Elastin A1 - T. Desman, Garrett A1 - Barnhill, Raymond L. A2 - Barnhill, Raymond L. A2 - Crowson, A. Neil A2 - Magro, Cynthia M. A2 - Piepkorn, Michael W. A2 - Kutzner, Heinz A2 - Desman, Garrett T. PY - 2020 T2 - Barnhill's Dermatopathology, 4e AB - The major function of the skin is to serve as a barrier to various exogenous substances, chemicals, and microbes. Collagen, ground substance (dermal mucin), and elastic fibers are the 3 major components of the dermis and are crucial to maintaining the integrity and elasticity of the skin. Collagen is the most abundant of the 3 components of the dermis (80% by dry weight), consisting primarily of type I collagen in the reticular dermis, type III collagen in the papillary and adventitial dermis, and type IV collagen forming basement membranes for epithelial structures and blood vessels. Over 20 distinct collagens are now recognized.1,2 The amino acid sequence and composition determines the individual collagen type. Collagens are composed of 3 polypeptides, or alpha chains, that assume a stabilizing triple-helical conformation depending on glycine residues located at every third position of the polypeptides. Hydroxyproline (synthesized from proline) is necessary for triple-helix stability at physiologic temperatures. Fibroblasts initially secrete collagen in a soluble form (procollagen), which is then cleaved to insoluble fibers (collagen) that are crosslinked by oxidation of lysyl and hydroxylysine residues. It is this crosslinking that gives collagen its tensile strength. Whereas type I collagen provides tensile strength to the skin, type III collagen participates in anchoring the epidermis and adnexae to the dermis. SN - PB - McGraw Hill Education CY - New York, NY Y2 - 2024/03/28 UR - dermatology.mhmedical.com/content.aspx?aid=1178393302 ER -