Mechanical modeling of the skin

Skin is a complex, multilayered material which is very difficult to study because of its great variability: it depends on individuals, but also on which body part one looks at. Even studying a small area, its behaviour varies with outside parameters (such as humidity) and aging. Let us describe its 3 main layers. 3 The epidermis: thickness 0.1mm, made of keratinocytes, which move from its bottom to its top and change of nature during this migration, to end up dying at the surface. No blood vessel. 3 The dermis: thickness: some mm, (15-20 % of the total body weight). Contains blood vessels, lymph vessels, nerve endings, hair follicles and hair muscles, sebaceous glands and sweat glands. Made of fibrin proteins (collagen, elastin) interacting with a surrounding matrix of ground substance, an amorphous gel which does not leak out from the skin, even under high pressure. 3 The hypodermis: thickness: fibrofatty layer (about 10 % of the total body weight) whose thickness varies a lot, depending on the location on the body (between 1 to tens mm)