The skin is one of the most important organs of the body. It serves as protection against infection by germs and shields delicate underlying tissue against injury, approximately one-third of the bloodstream flows through the skin, and as the blood vessel contract or relax in response to heat and cold, the skin acts as a thermostat, that helps control body temperature. The two million sweat glands in the skin also regulate body temperature through the evaporation of perspiration. The many delicate never endings in the skin make it a sense organ responsive not only to heat and cold but to pleasure, pain and pressure.
Certain cells in the skin produce a protective pigmentation that determines its colour and guards against overexposure to the ultraviolet rays of the sun, by absorption and elimination. The skin helps to regulate the body’s chemical and fluid balance. One of the miracles of the skin is that it constantly renews itself.
Structure of the skin
The skin is made up of two layers. The outer layers or the epidermis have a surface of horny, non-living cells. That forms the body’s protective envelope. These cells are constantly being shed and replaced by new ones which are made in the lower or inner layer of the epidermis.
Underneath the epidermis is the dermis, The thicker part of the skin, it contains blood vessels, nerves and connective tissues. The sweat glands are located in the dermis and they are called fluid containing water, salt and waste products from the blood, this fluid is sent through tiny canals that end in the pores on the skin surface.
The oil sebaceous glands that secreted the oil which lubricate the surface of the skin and hairs are also located in the dermis. They are most often associated with hair follicles. Hair follicles and oil glands are found over most of the body with the exception the palms of the hands and soles of the feet.
The layer of fatty tissue below the dermis called subcutaneous tissue acts as an insulator against heat and cold and a shock absorber injury.
The basic skin colour of each person is determined at birth and is a part of his/ her heritage that cannot be changed.
There are four pigments in normal skin that affects his / her colour: Melanin, Oxygenated haemoglobin, reduced haemoglobin and various carotenes of these. Melanin is the most powerful; it is there is a cell that produces variations in its colour which ranges from black to light tan. Every adult has about 60,000 melanin-producing cells in each square inch of skin.
Melanin cells also affect eye colour, in which if the cells are deer in the eye, the colour produced is blue or green, when they are close to the surface the eye is brown. An Albino person with no melanin has eyes that appear pink because the stronger pigment the gives blood its colour, called haemoglobin, has the next greatest effect on skin colour. When it is combined with oxygen, a bright red is a result and these, in turn, produces the rosy complexion associated with good health in light-skinned people. When such people suffer from reduced haemoglobin, it gives the skin a bluish appearance. Since haemoglobin has a weaker colouring effect than the melanin that determines basic skin colour. These variations are more visible in lighter skinned individuals.
The weakest pigments in the skin are the carotenes. These produce a yellowish tore that is increased by eating an excessive amount of carrots and oranges. In people with black and brown skin, excess carotene is usually masked by the melanin pigment.