the skin

• functions of the skin: protection:

  • epidermis protects from damage, prevents loss of water and entry of pathogens
  • dermis protects internal organs
  • melanin in the skin protects from UV rays
  • sebum (oil made in sebaceous glands) keeps hair moist and flexible and prevents skin from drying out and cracking
• functions of the skin: vitamin D:

  • produced in skin following exposure to UV rays
  • helps absorb calcium
• functions of the skin: food store:

  • fat in adipose tissue acts as food store
  • fat under the skin insulates the body
• functions of the skin: sense organ:

  • receptors in the skin allow detection of touch and temperature
• functions of the skin: excretion:

  • sweat glands act as organs of excretion
  • sweat is made of water and salts
• role of skin in homeostasis: temperature regulation

  role of skin in excretion: removal of sweat
• our body temperature is maintained at 37 degrees Celsius. the heat is produced by metabolism in the liver
• if our body temp rises:

  1. more blood flows close to surface of skin so heat is lost by radiation
  2. glands release sweat onto skin. this cools the skin by taking away some body heat when it evaporates

  • this loss of water must be replaced, which is why it is important to drink water before, during and after exercise.
  • what actually happens?: sweat is produced and released. the water evaporates and reduces the body temp. when too hot, vessels in the skin expand (dilate). this increases heat loss and reduces body temp.
• if our body temp drops:

  1. blood leaves surface layers and flows under the adipose tissue which insulates us so less heat is lost through the surface
  2. we stop sweating
  3. our hairs stand up causing goosebumps to insulate us with air
  4. we shiver (muscles contract to generate extra heat)

  • what actually happens?: skin retains heat. erector muscles contract, hair stands up on skin, piloerection. blood vessels in the skin contract, vasoconstriction, reduces heat loss through the skin. brain picks up on low temp and causes muscles to contract and relax quickly, shivering, which produces heat.