Integumentary system

• Integumentary system


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


  • 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
• Functions of skin


  • It inhibits excessive loss of water and electrolytes
  • It produces a protective pigmentation to protect the body against excessive exposure from the sun
  • It helps produce the body's supply of Vitamin D
  • It protects against invasion by bacteria and other harmful agents
  • It protects delicate cells beneath the surface from injury
• Skin regulates body temperature

  1. When the body is too hot, the blood vessels in the skin dilate to bring more blood to the surface for cooling by radiation, and sweat glands secrete more sweat that cools the body when it evaporates

  2. When the body is too cold, the skin's blood vessels constrict to allow more heat-carrying blood to circulate to the muscles and organs
• Skin provides sensations


  It contains millions of nerve endings that act as sensory receptors for pain, heat, cold, and pressure
• Layers of the epidermis

  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum germinativum
• Stratum corneum


  • It is the outermost strata of the epidermis, mostly dead cells filled with a protein substance called keratin, thicker on the soles of the feet than on the eyelids
• Stratum lucidum


  • It is a translucent layer lying directly beneath the corneum, may not even exist in thinner skin, cells are also dead or are in the process of dying
• Stratum granulosum


  • It is one or more layers of cells starting to die and become hard, in the process of keratinization (becoming fibrous protein similar to that in hair and nails)
• Stratum germinativum


  • It is the innermost layer of the epidermis, composed of several layers of living cells capable of cell division, contains melanin (the pigment that gives color to the skin), damage to this layer requires skin grafts
• Dermis


  • It contains the lymphatics, nerves, nerve endings, blood vessels, sebaceous and sweat glands, elastic fibers, and hair follicles, it is beneath the epidermis and is composed of connective tissue
• Layers of the dermis

  • Papillary layer (arranged into microscopic structures that form ridges, the finger- and footprints)
  • Reticular layer (beneath the papillary layer, a white fibrous tissue that supports the blood vessels)
• Hypodermis


  The subcutaneous tissue or hypodermis is composed of adipose and connective tissue, it supports, nourishes, insulates, and cushions the skin
• Hair


  • It 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 muscle


  • It is attached to the side of each hair follicle, stimulated by skin irritants, emotional arousal, or cold temperatures, and reacts by contracting to cause goose flesh or goose pimples
• Hair papilla


  • It is at the base of each hair follicle, enclosing a loop of capillaries, provides nourishment to the hair, one of the few living parts of the hair, responsible for hair growth
• Parts of the hair

  • Cuticle (covers the hair shaft like shingles, protects it from the elements and chemicals, and from losing moisture)
  • Cortex (provides most of the hair's weight, contains melanin which provides color, stores oils, provides flexibility and elasticity, and adds shape)
  • Medulla (inner hollow core that runs the length of the shaft)
• Sebaceous glands


  They are oil glands, have tiny ducts that open into each hair follicle, each gland secretes sebum which lubricates the hair and skin
• Parts of the nail

  • 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, where the growth occurs at approximately 1 mm per week)
  • Nail plate (body of the nail, has grooves that help anchor it)
  • Cuticle (also called the eponychium, fuses the nail plate and the skin of the finger together to form a waterproof barrier)
  • Hyponychium (under the free edge of the nail, also creates a waterproof barrier, fusing the skin of the finger to the underside of the nail plate)
• A lost finger- or toenail will regenerate
• Ingrown nail


  They are simply those that have curled down or around and are growing into the skin, may become swollen and inflamed
• Trim toenails straight across to avoid ingrown nail growth pattern
• Sudoriferous glands


  They 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 (underarms)
• Functions of sweat glands


  • They produce sweat or perspiration, as sweat collects on the skin surface it evaporates and creates a cooling effect
  • Sweat also rids the body of waste through the pores of the skin
  • As sweat accumulates, it may become odorous by the action of bacteria
  • The average person loses approximately 1/2 liter of fluid through sweating each day