The Skin Structure and Function:
The skin is the largest organ. It covers the whole body and is water-resistant. The skin consists of two layers; the Epidermis and Dermis (under which lies the subcutaneous or fatty layer).
The epidermis is the layer of skin that we can see. It varies in thickness. The thickest layer is on the soles of the feet and the palms of the hands. The thinnest layer is on the eyelids and nipples. The cells on the surface are constantly coming off (shedding) this is known as desquamation. They are also constantly being replaced from below as cells from the basal layer of the epidermis multiply and are pushed up to the surface. The basal layer of the epidermis receives its blood supply, nutrients and fluids from the dermis. There are five layers of the epidermis:
Stratum Corneum (surface):
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Normal body temperature is 37 degrees Celsius. Heat is absorbed and maintained in the subcutaneous layer of adipose tissue and regulated in the following ways:
• Cooling (vasodilation): when the body becomes hot, the capillaries dilate allowing more blood to reach the surface of the skin. The pores dilate allowing the heat to be lost from the body. This causes the skin to flush (known as hyperaemia). Sweating will occur simultaneously and the evaporation of perspiration from the skin’s surface has a cooling effect on the body.
• Warming (vasoconstriction): when cold the body protects itself by moving blood from the extremities to the vital organs, ensuring that they are kept warm. With the blood diverted to the major organs the capillaries and pores narrow, the skin appears pale and heat loss is prevented. The erector pili muscles contract, causing body hair to stand on end, trapping air against the surface of the skin, which is then warmed by body heat. Shivering occurs, caused by rapid and repeated muscle contractions which work to raise body temperature.