Skin

The skin is a specific multi-functional organ.

Function of the skin

The function of the skin is to cover the entire body in order to protect it.

Skin flora live naturally on the surface of the skin and protect it from pathogenic micro-organisms. The flora differ depending on the areas of the body (groin, hand, scalp).

The impermeable covering also provides protection together with the healing mechanism so that micro-organisms do not enter the body.

The skin is also a protective barrier against harmful sun rays. These rays activate melanocytes that are responsible for tanning. Vitamin D is produced by the skin as a result of sun rays.

The skin regulates body temperature by sweating which has the effect of removing heat. In contrast, hairs on the skin retain heat.

The skin also contains nerve structures that recognize pressure (touch), temperature and pain.

Skin structure

The surface area of the skin is 2 square meters and weighs 5 kilograms although these figures vary depending on a person's height and weight. The skin is vascularised and innervated. It also contains hairs in the hair follicles, sebaceous glands which lubricate the hairs and skin and pores allowing sweat to be removed.

The skin consists of three superimposed layers. From outside inwards these are:

• the epidermis is a thin epithelium (less than 1 millimetre) made up of dead keratinised cells which scale. It is not supplied directly by blood vessels but by diffusion from the dermis. It contains many nerve endings;
• the dermis is the;&nbsp thick connective tissue made up of proteins (collagen, fibronectin and elastin) and cells (fibroblasts, lymphocytes) bathed in a gel (made up of glycosaminoglycans) which hydrates the skin. It is involved in healing, heat regulation and sweating;
• The hypodermis is a richly vascularised connective tissue which contains larger or smaller amounts of adipose tissue. It is located between the upper layers of the skin and the mobile regions (muscles, tendons, etc). The hypodermis varies in thickness depending on the area of the body. The more the area is exposed to knocks, the thicker it is (heel, buttocks).