homeostasis

• define homeostasis


  the maintenance of a constant internal environment.
• describe the interior structure of the skin

  outer/top layer: epidermis

  inner/lower layer: dermis
• Cornified layer


  • Outer, hard and waterproof layer of dead cells
  • Reduces evaporation of water
  • Prevents bacteria from entering the body
• Granular layer


  1. Cells produced by the inner malpighian layer

  2. As new cells move towards the skin surface, they die, fill up with keratin and become part of the cornified layer
• Malpighian layer


  • Innermost layer of epidermis
  • Cells contain a dark pigment called melanin
  • Melanin gives the skin its colour and protects it from harmful UV rays
  • Divides and replaces worn out cells
• describe the structure of the inner dermis

  layer of connective tissue which contains elastic and collagen fibres.
• function of capillaries in inner dermis

  -bring food and oxygen to the skin

  -remove carbon dioxide and nitrogenous waste

  -regulate heat loss from body
• function of sweat glands in inner dermis

  -produces sweat which evaporates from the body by cooling down body

  -the gland consists of a coiled tube which takes up water from the capillaries. the sweat travels up the sweat duct to the surface of the skin
• describe the function of the hair in the inner dermis

  -traps a layer of air over the surface of the skin. since air is a bad conductor of heat, the hair helps prevent heat loss.

  • hair follicle = deep pit in the skin surface lined with granular and malpighian cells which divide and add more cells to the base of the hair extending out from the skin surface
• describe the function of the sebaceous gland in the inner dermis


  -produce an oily substance named sebum

  • the sebum keeps the epidermis waterproof and stops it from drying out
• describe the function of the fat deposits in the inner dermis


  -provides a store of food for the skin

  -acts as an insulating layer hence preventing heat loss
• list the functions of the skin


  -protection

  • against harmful UV rays
  • prevents entry of bacteria

  -sensitivity

  -temperature regulation

  -storage of fats and vitamin D

  -excretion of urea and other waste products
• how does the body hair react to cold weather ?

  
  

  -hairs are raised: erector muscles contract so the hairs are raised and trap a thick layer of air between them.

  -more heat is trapped in the body: our metabolic rate increases and we produce extra heat.

  -shivering: muscles contract and relax during shivering

  -vasoconstriction
• describe how the body reacts to warm weather

  -hairs are lowered

  -sweating: sweat glands produce more sweat which rises to the surface of the skin. water then evaporates by absorbing heat from the skin.

  -vasodilation
• which structure of the inner dermis is affected by climate the most?

  -hair erector muscle

  
• describe the function of the hypothalamus 


  the hypothalamus coordinates the activities of the parts of the body that can bring about temperature changes.

  -contains temperature receptors that sense the temperature of the blood running through it.
• why is a larger organism more skilled at conserving heat?

  the larger organism has a lower surface area to volume ratio than a small organism.

  
• label the following diagram

  .

  A) cornified layer

  B) hair erector muscle

  C) hair

  D) sebaceous gland

  E) fat deposits

  F) blood capillary

  G) sweat pore

  H) sweat gland

  I) pressure receptor

  J) hair follicle

  
• what is the biological term for a warm blooded organism?


  endothermic
• what is the biological term for a cold blooded organism?

  ectothermic
• define vasoconstriction


  -the blood vessels constricting so that more blood flow is passed through
• define vasodilation


  -the blood vessels widen so less blood passes through