Skin is the general covering of the entire external surface of the body, including the external auditory meatus and the outer surface of tympanic membrane.
The skin is continuous with the mucous membrane at the orifices of the body. The skin performs a large number of important functions, and consequently it is considered a very important organ of the body.
Surface area of skin:
In an adult human, the surface area of the skin is 1.5-2 square meters. The proportion of skin covering various parts of human body can be explained in percentages as:
- Head and Neck = 9%
- Each upper limb = 9%
- Front of the trunk = 18%
- Back of the trunk (including buttocks) = 18%
- Each lower limb = 18%
- Perineum =1%
This assessment is very important in cases involving burns, where the patient requires treatment according the magnitude of damaged area of skin.
Functions of skin:
The skin is the largest organ of human body and guards the underlying muscles, bones, ligaments and other delicate organs. Furthermore, the skin is in contact with the environment all the time and because of this reason, a healthy intact skin is very important for protection against the pathogens and other harmful agents.
The skin forms a water proof layer all around the body thus preventing excessive loss of water, which is vital for people living in deserts and dry places.
The skin contains a variety of receptors that react to different types of stimuli. The common sensations originated at the skin include: touch, pressure, hot, cold, vibration, injury etc.
Skin forms an important organ for regulation of heat. It receives far greater blood supply than is needed. This blood supply is precisely controlled. Whenever the body gets overheated, the blood supply to skin increases, and because the skin is in direct contact with the atmosphere, the heat from the blood is lost quickly and the temperature of the body is regulated. The sweating process further facilitates the cooling of blood.
The skin excretes small amount of urea in the form of sweat. The sweating process is primarily meant for regulating the temperature of body, however, excretion of urea is also achieved through it.