gas exchange

• structure of gas exchange in humans

  trachea → bronchi → bronchioles → alveoli
• what occurs in inspiration

  external intercostal muscle contracts

  internal intercostal muscle relaxes

  diaphragm contracts (flattens)

  ribs moves upwards + outwards

  lung volume increases

  volume of thorax increases

  air moves down the pressure gradient
• what occurs in expiration

  external intercostal muscles relaxes

  internal intercostal muscles contracts

  diaphragm relaxes

  ribs move inwards and downwards

  lung volume decreases

  volume of thorax decreases
• adaptations of the alveolar epithelium

  large surface area - contains a lot of air sacs

  short diffusion distance - one cell thick (epithelial cells)

  maintains conc. gradient - surrounded by a network capillaries
• anatomy of fish:

  • 4 layers of gills in each side of the head

   - gill filaments stacked & lamellae perpendicular to the gill filaments
• adaptations in fish

  large surface area to volume ratio: many gill filaments & gill lamellae

  short diffusion distance: thin gill lamellae & is surrounded by capillary network

  maintains conc. gradient: countercurrent flow principle
• countercurrent flow:

  1. Blood and water flow in opposite directions;

  2. maintain conc. gradient along (length of) lamella/filament;

  • ensures equilibrium is never reached
• structure of terrestrial insects

  waterproof exoskeleton - made of chitin - has a lipid layer 

  have no lungs - tracheal system:

  • spiracles → trachea → tracheoles
• ways of movement of gas in insects

  via diffusion

  muscles contract - moving gases in & out

  whilst flying - anaerobic respiration

  (lactate is produced, lowering water potential so water moves from tracheoles to cells by osmosis) - decreases volume in tracheoles drawing atm in
• limiting water loss in insects

  waterproof exoskeleton: lipid layer preventing water loss

  spiracles, open & close reducing water loss

  small SA:V ratio
• adaptations within insects:

  large surface area: many tracheoles

  short diffusion distance: short distance between spiracles and tracheoles & tracheoles has thin walls

  maintaining conc gradient: respiring cells use oxygen and produce carbon dioxide
• how can the dicotyledonous leaf limit water loss

  • stomata closes at night - no photosynthesis occurs so no evaporation can occur at night
• how does the xerophytic plant limit water loss

  curled leaves:

  • traps water that evaporates - increases humidity

  hairs:

  • traps water/moisture - increasing humidity - reduces evaporation (transpiration)

  sunken stomata:

  • traps moisture

  thicker cuticle:

  • traps moisture

  longer root network:

  • able to reach water from further distances
• difference of gas exchange system in fish and humans

  • fish consist of more oxygen than water leaving in the blood
  • fish remove a greater proportion of oxygen then they taken in
• adaptation to terrestial insects:

  • large surface area: many tracheoles
  • short diffusion distance: thin tracheoles
  • maintains conc. gradient: muscles contracts on its own to move gases
• circulation of fish v circulation of mammal

  • single v double
  • blood doesnt return to heart after oxygenated v does return to heart after oxygenated
  • 2 chamber v 4 chambers