Anatomy and Physiology of the Skin

Abstract

The human body is protected by the skin, a continuous covering which at level of the natural orifices (eyelids, nostrils, lips, urinary meatus, vulva, anus) gradually changes its structure to assume the histological characteristics of the internal mucosa. The functions of the skin are essential for the maintenance of life so that it can be considered a true and complex organ. In an adult standard man (70 kg) it comprises 4% of the body weight, while its surface extends for 1.6–2 m². The skin thickness varies from 10 μm on the eardrum, to 1 mm on the eyelids, to 3–4 mm on the nape. Generally, it is more thick in some particular regions as back, palm, sole. Skin is elastic, and its smooth, soft and pliable surface is broken by intersetting lines, folds, ridges and pores. It is well known the uniqueness of the palmar ridge patterns for each individual, which allows the personal identification by means of the fingerprint patterns. The lost of elasticity, and an increase of folds and ridges are characteristic of the skin aging, together with the appearance of brownish stains. The colour of the skin is largely variable according to the race, sex, age, vasodilatation, effort, emotional state, natural and artificial pigment changes, health state and all possible combinations of these different conditions.