Human Skin

Human Skin, in human anatomy, the covering, or integument, of the body’s surface that both provides protection and receives sensory stimuli from the external environment.

In adults, skin accounts for about 16 percent of total body weight and covers a surface area of approximately 22 square feet (2 square meters).

Human skin is composed of three layers of tissue: the epidermis, dermis and hypodermic.

Epidermis

The epidermis is the top, visible of skin and it’s constantly being renewed as dead skin cells are shed on a daily basis. The main functions of the epidermis include:

Making new skin cells. New skin cells form at the bottom of the epidermis. As these newer cells form, it takes them about one month to reach the top layer of the epidermis. The new cells will replace the old cells found on the skin surface, which are dead and continuously flake off.

Giving skin its colour. The epidermis contains melanocytes, which are cells that produce melanin, the pigment that gives skin its colour. Melanin is also responsible for suntans and freckles.

Protecting skin. Keratin, a protein made by cells found in the epidermis, gives skin its toughness and strength, and protects skin from drying out.

Dermis

The dermis is the middle layer of skin, found underneath the epidermis. It is the thickest layer of the skin and contains nerves and blood vessels. It is also home to the sweat glands, oil glands and hair follicles. The dermis gives skin its flexibility and strength, according to the John Hopkins Medicine Health Library. It is made up mostly of a protein called collagen that makes skin stretchy and strong.

The roles of the dermis include:

Sensing pain and touch. Nerve endings in the dermis contain receptors that transmit sensations, such as pain, pressure, touch, itchiness and temperature to the brain.

Producing sweat and oils. Sweat glands help to cool the body, and sebaceous glands make the oils that keep skin soft and moist.

Growing hair. Hair follicles found in the dermis grow the hair on your head, face and body. That hair also helps to control body temperature and protect the body from injury.

Bringing blood to the skin. Blood vessels found in the dermis nourish the skin and help control body temperature. When skin becomes too hot, blood vessels enlarge to release heat from the skin’s surface while cold constricts blood vessels so the retain body heat.