Skin: The Protective Cover of Body
Skin is the largest organ of the body. It is most delicate and with its fleshy coverings, makes people look presentable. While organs like brain, heart and kidney are internal, skin can be seen from outside. Adults carry about 8 pounds (3.6 kg) of skin. Skin serves as a protective layer in our body. Without it, human body would evaporate.
Functions of Skin
Skin performs a wide variety of functions in our daily life. Its primary functions can be broadly summarized as under:
- Skin is a waterproof, insulating protection which guards our body against extreme temperatures, damaging sunlight and other harmful particles.
- With its fine shield, skin prevents harmful particles from entering our body.
- It also radiates anti-bacterial substances, thereby preventing infection.
- Skin manufactures Vitamin D which converts into healthy bones.
- Skin is also a huge sensor, packed with sensory nerves that keep brain in contact with the outside world.
- Finally, skin allows us to move freely due to its high versatility.
Layers of Skin
Skin consist of three different layers-epidermis, dermis and subcutis. The outermost layer is known as epidermis. It mainly consists of cells, known as keratinocytes. Keratinocytes are made of keratin, a tough protein, which is also present in hairs and nails. Several layers are formed in the keratinocytes which constantly grow outwards, as exterior cells deteriorate and die. It takes almost five weeks to form new cells and make their way to the surface. The covering of dead skin is called stratum corneum. It is a horny layer with varied thickness around the body. Dead skin can be more than ten times thicker on the feet soles than around the eyes. Defensive Langerhans cells reside in the epidermis. The main purpose of these cells is to alert the immune system of body against bacteria, viruses and other infectious agents.
The epidermis is what we see. It is connected to a deeper skin layer known as dermis. Collagen fibers and elastin present in the dermis provide strength and elasticity to the skin. The blood vessels help in regulating body temperature by enhancing blood flow to the skin to enable heat to escape,or by restricting blood flow, when it’s cold. Beneath the epidermis, lies a network of nerve fibers and receptors which stimulate feelings of touch, pain and temperature and relays them to the brain.
In the dermis, there are hair follicles and glands along with ducts, which pass throughout the skin. Dermis also houses the sweat glands which helps to bring down the internal temperature through perspiration and simultaneously removes waste fluids like urea and lactate from the body. The apocrine glands, also present in this region, are responsible for producing scented sweat associated with sexual attraction. This also causes body odor, especially around the armpits. Apocrine glands develop during puberty. The sebaceous glands secrete oil-like serum which lubricates hair and skin.
The base layer of the skin is called subcutis. It includes a stratum of fat which serve as a reserve of fuel, during food shortage. An insulating layer, the subcutis cushions us from falls and knocks.
Skin gets its color, from a pigment called melanin. Melanin is produced in the epidermis and protects us from the harmful ultraviolet (UV) rays of the sun, which also has a potential to cause cancer. Dark-skinned people have more number of melanin pigments than fair-skinned. People belonging to tropical regions especially densely forested areas, have darker complexions. In northern latitudes where solar radiation is comparatively weak, fair skin is more common. However, the advantages of dark-skin are completely overshadowed by the strong need for Vitamin D for strengthening bones. Vitamin D is produced on exposure to UV rays.
Regions which are hot, humid and sunny poses serious threat to the skin. Australia has the world’s highest record of skin cancer, with more than 80% of all cancers being diagnosed each year. A majority of Northern European population inhabits Australia.