Glands

The skin contains exocrine glands, glands that release secretions through ducts. The main exocrine glands of the skin are the sweat glands and the oil glands.

The skin functions as an excretory organ by releasing excess water, salts, and urea through the sweat glands. By releasing excess water, the skin also helps regulate body temperature. When the body's temperature rises, circulation increases, and the skin becomes warm and flushed, as shown in Figure 45-16. The sweat glands then release more sweat. As the water in sweat evaporates, the skin is cooled.

Oil glands, found in large numbers on the face and scalp, secrete the fatty substance sebum. Oil glands are usually connected by tiny ducts to hair follicles. Sebum coats the surface of the skin and the shafts of hairs, preventing excess water loss and softening the skin and hair. Sebum is also mildly toxic to some bacteria. The production of sebum is controlled by hormones. During adolescence, high levels of sex hormones increase the activity of the oil glands. If the ducts of oil glands become clogged with excessive amounts of sebum, dead cells, and bacteria, the skin disorder acne can result.

Skin is composed of two layers: the epidermis and the dermis. The top of the epidermis consists of dead, flattened cells that are shed and replaced every day. The dermis contains specialized structures that protect the body from infectious diseases, regulate body temperature, sense the environment, and secrete oil, sweat, and some wastes.

figure 45-16

Skin acts as a temperature-controlling device. It contains millions of sweat glands that secrete microscopic droplets of water. The water droplets help cool the body when its temperature rises, such as after a rigorous workout.

figure 4s-17

This illustration of the structure of a fingernail shows that the nail root, from which the nail is constantly regenerated, is protected well beneath the surface of the finger, next to the bone of the fingertip.

Nail root

Phalanx (bone of the fingertip)

Eponychium (cuticle) Lunula

Nail body

Nail body

Phalanx (bone of the fingertip)

Nail bed Free edge

Hyponychium

Nail bed Free edge

Hyponychium

Fight Acne

Fight Acne

I am sure that every one of you is familiar with acne. Almost all of us got this skin disorder, right? Well, technically known as acne vulgaris, this skin disorder affects millions of people from different walks of life, annually.

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