The Functions of the Skin

Skin is a waterproof, flexible, but tough protective covering for your body. Normally the surface is smooth, punctuated only with hair and pores for sweat. A cross-section of skin shows the major parts. It is divided into three layers. The outer layer is the epidermis. The dermis is in the middle and fat forms the innermost layer. Blood vessels, nerves, hair follicles, oil glands and sweat glands are located in the dermis.

The major function of skin is to provide a barrier between you and the outside environment. Without this protective covering, your life on earth would be impossible. The outermost layer of the epidermis is made up of sheets of dead cells that serve as the major waterproof barrier to the environment. In addition, special cells called melanocytes inside the epidermis produce brown pigment which helps protect you from ultraviolet light.

Skin is a dynamic, protective organ that grows, stretches, shrinks, creases, and wrinkles in response to a person’s age, habits, weight fluctuations, and the environment. The skin, capable of self-regeneration, is the only organ in the human body that is constantly exposed to the external environment. Skin serves several functions, which are introduced here.

1. Regulation of body temperature
Temperature regulation is important, as various organs, including our brain can not operate outside a certain temperature range.
It also helps human body to maintain normal temperature: its numerous sweat glands excrete waste products along with salt-laden moisture, the evaporation of which may account, in certain circumstances, for as much as 90% of the cooling of the body; its fat cells act as insulation against cold; and when the body overheats, the skin's extensive small blood vessels carry warm blood near the surface where it is cooled.

2. Protection
The skin protects underlying tissues and organs from abrasion and other injury, and its pigments shield the body from the dangerous ultraviolet rays in sunlight. Hair and nails also have protective functions. Our skin is a shield that protects us from:

• mechanical impact such as pressure and stroke
• thermic impact such as heat or cold
• environmental impact such as chemicals, the sun´s UV-radiation and bacteria

3. Sensation
The skin contains abundant nerve endings and receptors that detect stimuli related to temperature, touch, pressure, and pain. It is helping the body sense touch, pain, temperature, pressure, and position.

4. Excretion
Besides removing heat and some water from the body, sweat also is the vehicle for excretion of a small amount of salts and several organic compounds. skin also prevents excessive fluid and electrolyte loss.

5. Immunity
Certain cells of the epidermis are important components of the immune system, which fends off foreign invaders.

6. Blood reservoir
The dermis of the skin houses extensive networks of blood vessels that carry 8 to 10% of the total blood flow in a resting adult. In moderate exercise, skin blood flow may increase, which helps dissipate heat from the body. During hard exercise, however, skin blood vessels constrict (narrow) somewhat, and more blood is able to circulate to contracting muscles.

7. Synthesis of Vitamin D
Vitamin D is a group of closely related compounds. Synthesis of vitamin D begins with activation of a precursor molecule in the skin by ultraviolet (UV) rays in sunlight. Enzymes in the liver and kidneys then modify the molecule, finally producing calcitriol, the most active form of vitamin D. Therefore, vitamin D is a hormone, since it is produced in one location in the body, transported by the blood, and then exerts its effect in another locations. In this respect, the skin may be considered an endocrine organ (hormone producing organ or gland).

On a psychological level, your skin is the most active link with your surroundings. Quite apart from its role in your personal appearance, the skin is vital in conveying the sense of touch and forms the principal organ of sexual attraction and communication.