The skin.

First thing first, the biology of the skin.

Skin is the largest organ of the human body. It is a continuous membrane or sheet covering the entire body surface which composed of two main layers, the epidermis and dermis. The thickness of the two layers varies over different regions of the body in which the epidermis is thickest on the palms and soles of the feet whereas the dermis is thickest on the back and thinnest on the palms.

The epidermis is the uppermost layer that generates the stratum corneum which provides the skin’s protective barrier. This membrane prevents extraneous materials getting into the body as well as controls and prevents the loss of materials from within the skin. The dermis is the thick, fibrous layer beneath the epidermis that contains blood vessels, hair follicles and glands that produce sweat, which helps regulate body temperature and sebum, an oily substance that helps keep the skin from drying out. It also contains several connective tissue proteins which are collagens, elastin and proteoglycans. Collagen covers the body, elastin provides elasticity and strength while proteoglycans are involved in damage repair.

The third and bottom layer of the skin is called the subcutaneous layer which is made mostly of fat and helps your body to stay warm and absorb shocks, like if you bang into something or fall down. The subcutaneous layer also helps hold your skin to all the tissues underneath it.

New skin cells are produced at the bottom of the epidermis, and it moves upward when it matures. In the process, it loses moisture and flattens out until it is exposed at the topmost layer of the skin. This becomes a barrier against moisture loss and environmental damage. The cycle of cell renewal takes about 28 days, but the process takes longer as we age. The cycle or rate balance of these cell renewals is important in order to maintain a healthy skin barrier.