WHAT IS THE SKIN?

The skin is the largest single organ in the human body. It comprises up to 15 per cent of the total body weight, and if more than about one quarter is destroyed, by burns for example, then the body cannot survive. As well as being an extremely waterproof, air-tight, and remarkably supple barrier, the skin is also the living interface between man and his environment.

Indeed, the skin is as important an organ as the heart, lungs or brain. Its principal functions are protection, sensation, and heat regulation. Every living thing, however, is fragile and perishable; everything which functions can break down. The skin is no exception, and being in direct contact with the outside world, it is continuously exposed to all manner of injury. When you consider that it is susceptible to diseases resulting from various internal disorders as well, it is not surprising that its equilibrium, threatened from within and without, is precarious and easily upset. Care is required to keep the skin in good condition, and this requires some knowledge of the skin’s nature and needs.

The skin is a complicated membrane composed of various layers containing a variety of glands, blood vessels, nerves, lymphatics, muscles and appendages. The most superficial layer is known as the epidermis, which is made up of a mosaic of cells varying in thickness from 0-1 millimetre on the eyelid to more than 1-0 millimetre on the sole of the foot. The average thickness would be about that of this page. The deepest cells make up what is known as the basal layer, which is only one cell thick. This is the layer where cell reproduction takes place, and the regrowth of skin occurs. It normally takes about one month for a cell born in the basal layer to be shed as a used and dead cell at the surface. Within this important basal layer of the epidermis are scattered the melanocytes, which are the important melanin or pigment forming cells of the skin. These, according to then-quantity, dictate the colour of a person’s skin.

Beneath the epidermis is the dermis, which is 20 to 30 times thicker than the epidermis and rests upon a thick pad of fatty subcutaneous tissue which acts as a shock absorber and heat insulator. The dermis is extremely important, being made up of specialized connective tissue. Broadly speaking, it is composed of two sorts of fibres. The majority are grouped bundles, forming undulating, interlacing bands, and are composed of a special protein called collagen. Intermingled with these is a network of other fibres, which are thin, sinuous, and elastic, and composed of a protein called elastin. These fibres make up only 2 per cent of the connective tissue, the remainder consisting of what is called ground substance. This is the gelatinous material between the fibres, which is produced by specific cells known as fibroblasts. It is a unique material comprised of proteins, sugars, and electrolytes. The amount of ground substance is greatest in the embryo, and from then on it gradually diminishes until old age, when very little remains.

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