Biology- Integumentary System

PARTS OF THE INTEGUMENTARY SYSTEM

Integument comes from the Latin word integumentum , meaning "cover" or "enclosure." In animals and plants, an integument is any natural outer covering, such as skin, shell, membrane, or husk. The human integumentary system is an external body covering, but also much more. It protects, nourishes, insulates, and cushions. It is absolutely essential to life. Without it, an individual would be attacked immediately by bacteria and die from heat and water loss.

The integumentary system is composed primarily of the skin and accessory structures. Those structures include hair, nails, and certain exocrine glands (glands that have ducts or tubes that carry their secretions to the surface of the skin or into body cavities for elimination).

Skin

Although the skin is not often thought of as an organ, such as the heart or liver, medically it is. An organ is any part of the body formed of two or more tissues that performs a specialized function. As an organ, the skin is the largest and heaviest in the body. In an average adult, the skin covers about 21.5 square feet (2 square meters) and accounts for approximately 7 percent of body weight, or about 11 pounds (5 kilograms) in a 160-pound (73-kilogram) person. It ranges in thickness from 0.04 to 0.08 inches (1 to 2 millimeters), but can measure up to 0.2 inches (6 millimeters) thick on the palms of the hands and the soles of the feet. The skin in these areas is referred to as thick skin (skin elsewhere on the body is called thin skin).

Apocrine sweat glands (AP-oh-krin):

Sweat glands located primarily in the armpit and genital areas.

Arrector pili muscle (ah-REK-tor PI-li):

Smooth muscle attached to a hair follicle that, when stimulated, pulls on the follicle, causing the hair shaft to stand upright.

Dermal papillae (DER-mal pah-PILL-ee):

Finger-like projections extending upward from the dermis containing blood capillaries, which provide nutrients for the lower layer of the...