Additional Notes on the Integumentary System and Vocabulary Work

Skin Intro

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.  Skins contains all four major tissue types.

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).

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 epidermis; also form the characteristic ridges on the skin surface of the hands (fingerprints) and feet.

Dermis (DER-miss): Thick, inner layer of the skin.

Eccrine sweat glands (ECK-rin): Body's most numerous sweat glands, which produce watery sweat to maintain normal body temperature.

Epidermis (ep-i-DER-miss): Thin, outer layer of the skin.

Epithelial tissue (ep-i-THEE-lee-al): Tissue that covers the internal and external surfaces of the body and also forms glandular organs.

Integument (in-TEG-ye-ment): In animals and plants, any natural outer covering, such as skin, shell, membrane, or husk.

Keratin (KER-ah-tin): Tough, fibrous, water-resistant protein that forms the outer layers of hair, calluses, and nails and coats the surface of the skin.

Lunula (LOO-noo-la): White, crescent-shaped area of the nail bed near the nail root.

Melanocyte (MEL-ah-no-site): Cell found in the lower epidermis that produces the protein pigment melanin.

Organ (OR-gan): Any part of the body formed of two or more tissues that performs a specialized function.

Sebaceous gland (suh-BAY-shus): Exocrine gland in the dermis that produces sebum.

Sebum (SEE-bum): Mixture of oily substances and fragmented cells secreted by sebaceous glands.

Squamous cells (SKWA-mus): Cells that are flat and scalelike.

Subcutaneous (sub-kew-TAY-nee-us): Tissues between the dermis and the muscles.

The skin has two principal layers: the epidermis and the dermis. The epidermis is the thin, outer layer, and the dermis is the thicker, inner layer.

Beneath the dermis lies the subcutaneous layer or hypodermis, which is composed of adipose or fatty tissue. Although not technically part of the skin, it does anchor the skin to the underlying muscles. It also contains the major blood vessels that supply the dermis and houses many white blood cells, which destroy foreign invaders that have entered the body through breaks in the skin.

Regena