Skin

Article By:

Bennett, Albert F. Department of Ecology and Evolutionary Biology, University of California, Irvine, California.

Last reviewed:August 2021

DOI:https://doi.org/10.1036/1097-8542.627000

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• Skin, published June 2014:Download PDF Get Adobe Acrobat Reader

The entire outer surface of a vertebrate animal (including humans), and the principal boundary between the external environment and the body's internal environment of cells and fluids. Skin (Fig. 1) serves as the primary barrier against the intrusion of foreign elements and organisms into the body of a vertebrate animal (including humans). It also serves as a large and complex sense organ through which vertebrates explore and learn about the external world. In addition, skin functions to maintain the homeostasis of the body's constituents, acting as a barrier to the loss of various ions and nutrients by diffusion. In certain animals, skin also serves as a minor excretory organ to rid the body of wastes and excess salts (via sweat glands). Importantly, for terrestrial vertebrate animals, it acts as an effective barrier to water loss, without which most land animals would rapidly become desiccated and die. In general, the skin of vertebrates can be divided into epidermal and dermal regions. However, the detailed anatomy within this basic bilayer organization differs among the various vertebrate groups (classes). See also: Cutaneous sensation; Homeostasis; Sensation; Sense organ; Skin disorders; Vertebrata

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