Integumentary

• Integumentary system


  Consists of the skin and its accessory structures, including the hair, nails, sebaceous glands, and sweat glands

  
• Skin


  • It is the exterior covering of the body
  • It weighs more than 6 pounds in the average adult
  • It covers more than 3,000 square inches
  • It is the largest organ of the body
  • It is supplied with blood vessels and nerves

  
• 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
• Skin


  • 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


  • It provides sensations
  • It contains millions of nerve endings that act as sensory receptors for pain, heat, cold, and pressure
  • When stimulation occurs, nerve impulses are sent to the cerebral cortex of the brain and the brain triggers any necessary response
• Epidermis


  The outermost layer of the skin

  
• Layers of the epidermis

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


  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


  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


  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


  Composed of several layers of living cells capable of cell division, the innermost layer of the epidermis, contains melanin (the pigment that gives color to the skin)
• Dermis


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

  
• Layers of the dermis

  • Papillary layer
  • Reticular layer

  
• Papillary layer


  Arranged into microscopic structures that form ridges, these are the finger- and footprints

  
• Reticular layer


  Beneath the papillary layer, a white fibrous tissue that supports the blood vessels
• Subcutaneous tissue (hypodermis)


  Composed of adipose and connective tissue, supports, nourishes, insulates, and cushions the skin

  
• Hair


  • 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


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


  At the base of each hair follicle, a bulb enclosing a loop of capillaries that provides nourishment to the hair, one of the few living parts of the hair and responsible for hair growth
• Hair structure


  • The transparent cuticle covers the hair shaft like shingles on a roof, protecting it and preventing moisture loss
  • The cortex provides most of the hair's weight, contains melanin which provides color, stores oils, provides flexibility and elasticity, and adds shape to the hair
  • The medulla is a inner hollow core that runs the length of the shaft
• Sebaceous glands


  Oil glands that have tiny ducts that open into each hair follicle, secreting sebum to lubricate the hair and skin
• Nails


  • 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, where growth occurs at approximately 1 mm. per week
  • The under-surface of the nail plate or body of the nail has grooves that help anchor it
  • The cuticle, also called the eponychium, fuses the nail plate and the skin of the finger together to form a waterproof barrier
  • The hyponychium is under the free edge of the nail and 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 nails


  Nails that have curled down or around and are growing into the skin, may become swollen and inflamed, can be avoided by trimming toenails straight across
• Sudoriferous glands (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), produce sweat or perspiration that evaporates to create a cooling effect and rid the body of waste
• As sweat accumulates, it may become odorous by the action of bacteria
• The average person loses approximately ½ liter of fluid through sweating each day