SKIN

Covering an average of 20 square feet, the skin is the body’s largest and heaviest organ. Its most obvious job is to protect our insides from the outside, but there is much more to the skin than that.Alongside its role as a protective barrier, the skin helps us maintain the right internal temperature and allows us to sense the world through nerve endings. Skin is a complex organ; an average square inch of skin contains 650 sweat glands, 20 blood vessels, and more than 1,000 nerve endings. Despite being just a few millimeters thick, skin makes up around one-seventh of our body weight.

SKIN LAYERS

The skin has three basic levels the epidermis, dermis and hypodermics.

EPIDERMIS

Main roles: makes new skin cells, gives skin its color and protects the body.

The epidermis is the outermost layer; it is a waterproof barrier that gives skin its tone.

New cells are made in the lower layers of the epidermis. Over the course of around 4 weeks, they make their way to the surface, become hard, and replace the dead cells as they are shed.

Keratinocytes are the most common cell type within the epidermis; their job is to act as a barrier against bacteria, parasites, fungi, viruses, heat, ultraviolet (UV) rays from the sun, and water loss.

The epidermis is subdivided into five layers:

• stratum corneum
• stratum lucidum
• stratum granulosum
• stratum spinosum
• stratum germinativum

DERMIS

Main roles: makes sweat and oil, provides sensations and blood to the skin and grows hair.

SUBCUTANEOUS TISSUE

Main roles: attaches dermis to the body, controls body temperature and stores fat.

SKIN COLOR

People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin.The genetic mechanism behind human skin color is mainly regulated by enzyme tyrosinase which created the color of the skin, eyes, and hair shades. Difference in skin color are also attributed to differences in size and distribution of melanosomes in the skin. Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance. Each gene can come several alleles, resulting in the great variety of human skin tones. Melanin controls the amount of ultraviolet (UV) radiation from the sun that penetrated the skin by absorption