Anatomy and Physiology: Integumentary System

• The integumentary system consists of the skin and its accessory structures, including the hair, nails, sebaceous glands, and sweat glands.
• The skin is the

  exterior covering of the body. It weighs more than 6 pounds in the average adult, and covers more than

  3,000 square inches.

  It is the largest organ of the body. It is supplied with blood vessels and nerves.
• The skin has two layers... the epidermis and the dermis.

  The epidermis actually has 4 străta
• The stratum corneum

  (STRĂT um KOR nee um) is the outermost strata of the epidermis. It is mostly dead cells, filled with a protein substance called keratin. It is thicker on the soles of the feet than on the eyelids... where there is less pressure.
• The stratum lucidum

  (LOO seh dum) is a translucent layer lying directly beneath the

  corneum. It may not even exist in thinner skin. Cells in this layer are also dead or are in the process of dying.
• The stratum granulosum (grăn yu LO sum) is one or more layers of cells starting to die and become hard. They are in the process of

  keratinization... (kare ah tin i ZA shun)

  becoming fibrous protein similar to that in hair and nails.
• The stratum germinativum (fer mah nah Tivum) is composed of several layers of living cells capable of cell division. It is the innermost layer of the epidermis, and contains melanin... the pigment that gives color to the skin. The more abundant the melanin... the darker the skin color.

  Damage to this layer, such as in severe burns, requires skin grafts.
• The dermis is beneath the epidermis and is composed of connective tissue.
• The dermis

  it contains the lymphatics, nerves, nerve endings, blood vessels, sebaceous and sweat glands, elastic fibers, and hair follicles
• (dermis)the papillary layer (PĂP ah lair ee) is arranged into microscopic structures that form ridges. These are the finger- and footprints
• (dermis) The reticular layer    (ruh TĬK yoo ler) is beneath the papillary  layer;  it is a white fibrous tissue that supports the blood vessels
• The subcutaneous tissue or hypodermis is composed of adipose and connective tissue. It supports, nourishes, insulates, and cushions the skin.
• The hair is a threadlike structure formed by a group of cells that develop within a hair follicle or socket.  Each hair has a shaft that is visible and a root that is embedded in the follicle.
• pilomotor (pī lah MŌ ter) muscle is attached to the side of each follicle. It is stimulated by skin irritants, emotional arousal, or cold temperatures, and reacts by contracting. This causes goose flesh or goose pimples
• At the base of each hair follicle is a bulb enclosing a loop of capillaries.  It is called the hair papilla                 (pah PILL ah), and provides nourishment to the hair.  It is one of the few living parts of the hair, and is responsible for hair growth.
• Sebaceous (sǐ BAY shuss) glands are oil glands. They have tiny ducts that open into each hair follicle.
• Each sebaceous gland secretes sebum, which lubricates the hair and skin. The amount of secretion varies with age, puberty, and pregnancy.
• Fingernails and toenails are hard keratin structures that protect the ends of the fingers and toes.  The nail root, also called the germinal matrix or nailbed, begins several millimeters into the finger and extends to the edge of the white, crescent-shaped lunula. This is where the growth occurs…  approximately 1 mm. per week.  
• The cuticle is also called the eponychium        (ep ǐ NĬK ee um). It fuses the nail plate and the skin of the finger together to form a waterproof barrier.

  The hyponychium (hī poh NĬK ee um)  is under the free edge of the nail.  It also creates a waterproof barrier, fusing the skin of the finger to the underside of the nail
• Ingrown nails are simply those that have curled down or around and are growing into the skin. They may become swollen and inflamed. Trim toenails straight across to avoid this growth pattern.
• Sudoriferous  (soo door RĬF or us) glands are sweat glands. About 2 million are distributed over the surface of the body, more numerous on the palms of the hands, soles of the feet, forehead, and axillae (AG zil ah) or underarms.
• The average person loses approximately ½ liter of fluid through sweating each day