FUNCTIONS OF SKIN -
Skin performs various diverse functions, that is why it is called "jack of all trades".
1. Protection - The skin protects the internal soft organs from mechanical injuries.
2. Prevention of water loss - The skin prevents loss of water (dehydration) from internal organs.
3. Maintenance of body form - The skin helps in maintenance of the body shape.
4. Barrier to germs and poisons- The skin prevents the entry of micro-organisms and absorption of poisonous materials.
5. Safety against sunburn - Melanin of the epidermal cells protects against the invisible ultra violet rays of the sun.
6. Chemical defence - The sweat oil and wax 'of cutaneous glands contain lactic acid and fatty acids which make the pH acidic enough to kill or slow down growth of many bacteria and fungi.
7. Thermoregulation (Regulation of body temperature) - The normal body temperature of man is 98.4°F (=37°C).
It is maintained in both summer and winter seasons. In summer the cutaneous blood vessels dilate which causes loss of heat. The sweat is vaporised from the surface of the skin which decreases its temperature. In winter the cutaneous blood vessels constrict and thereby less heat is lost from the body. The subcutaneous fat conserves body heat.
8. Excretion and Homeostasis - Sweat secreted by sweat glands is excretory product (metabolic wastes). During ecdysis (removal of epidermal cells from stratum corneum), keratin (formed from waste proteins) is removed which is also an excretory product. Removal of metabolic wastes helps in keeping the internal environment of the body constant (homeostasis).
9. Secretion - Human cutaneous glands secrete sebum, sweat, milk, ear wax, etc.
10. Sensation - The skin has abundant receptors for touch, heat, cold, pain, pressure, etc.
11. Synthesis of Vitamin D - The skin is capable of forming vitamin D from a cholesterol derivative in the presence of sunlight.
12. Formation of bones and teeth - Dermis of the skin gives rise to the dermal bones of the skull. Teeth are formed from both the epidermis and the dermis.
13. Aid in physical examination - Yellowish colour of skin indicates jaundice. Certain rashes or lesions show infectious disease like measles, chicken pox, small pox, syphilis, allergy etc. The skin also reveals age of the person.
14. Storage of food - The subdermal portion of the skin stores fat.
15. Absorption - The skin can absorb oil, ointments, etc. through the opening of sweat glands and hair follicles, if applied and rubbed. The skin also absorbs light for the benefit of internal tissues.
16. Colour - Melanin in the epidermal cells give colour to the skin.
17. Healing of Wounds - The epidermis of the skin has a great power of regeneration. It helps in rapid healing of wounds.