The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold. 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. The skin consists of three layers of tissue: the epidermis, an outermost layer that contains the primary protective structure, the stratum corneum; the dermis, a fibrous layer that supports and strengthens the epidermis; and the subcutis, a subcutaneous layer of fat beneath the dermis that supplies nutrients to the other two layers and that cushions and insulates the body.
Skin has three layers:
- The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.
- The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
- The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis.
How It Protects The Body
Skin is made up of three layers. The outermost is the epidermis. This consists mainly of cells called keratinocytes, made from the tough protein keratin (also the material in hair and nails). Keratinocytes form several layers that constantly grow outwards as the exterior cells die and flake off. It takes roughly five weeks for newly created cells to work their way to the surface. This covering of dead skin is known as the stratum corneum, or horny layer, and its thickness varies considerably, being more than ten times thicker on the soles of the feet than around the eyes. The epidermis harbors defensive Langerhans cells, which alert the body’s immune system to viruses and other infectious agents.
The epidermis is bonded to a deeper skin layer below known as the dermis, which gives the organ its strength and elasticity thanks to fibers of collagen and elastin. Blood vessels here help regulate body temperature by increasing blood flow to the skin to allow heat to escape, or by restricting the flow when it’s cold. A network of nerve fibers and receptors pick up feelings such as touch, temperature, and pain, relaying them to the brain.
The dermis houses hair follicles and glands with ducts that pass up through the skin. Sweat glands bring down internal temperature through perspiration while ridding the body of the waste fluids urea and lactate. Apocrine glands, which develop during puberty, produce a scented sweat linked to sexual attraction that can also cause body odor, especially around the armpits. Sebaceous glands secrete oil-like sebum for lubricating the hair and skin.
The skin’s base layer is the subcutis, which includes a seam of fat laid down as a fuel reserve in case of food shortage. It also works as insulation and cushions us from knocks and falls.
