ventilation & gas exchange

• gas exchange:

  • short diffusion pathway
  • large surface area
  • large concentration gradient
  • moist walls
  • thin walls
  • permeable to gases involved
• Gas exchange in bony fish:

  • single circulatory
  • e.g trout, salmon and cod
  • large and very active = high oxygen requirement
  • Water travels in through the mouth and out through the operculum
  • one direction travel
  • gills supported by gill bar (made of cartilage)
  • space between gill bars are called gill splits
  • each grill has two rows of filaments (covered in lamellae)
• Gas exchange in bony fish:

  • as water passes through the gills the gas exchange occurs in the lamellae
  • in the lamellae, the distance between the water and the blood is 5um
  • gills provide large surface area
  • gills have an extensive network of blood capillaries to maximise diffusion
  • oxygen from water diffuses into the blood. CO2 diffuses from the blood to the water
• Countercurrent flow:

  • blood and water flow over lamellae in opposite directions
  • this mean when oxygen rich blood meets oxygen rich water, maximising diffusion of oxygen into blood
  • oxygen poor blood from body tissues meets oxygen reduced water still allowing diffusion
  • maintains concentration gradient
• Ventilation in bony fish:

  1. mouth opens and operculum closes
  2. buccal floor lowers so the buccal cavity volume increases. As volume increases, pressure decreases and water flows in
  3. mouth closes
  4. buccal floor raises so pressure increases
  5. operculum opens so the water is pushed out through the gills
• Gas exchange in insects:

  very active = high oxygen requirement

  tough exoskeleton through which little gas exchange can take place

  system adapted to deliver oxygen directly to tissues
• Gas exchange in insects:

  1. air enters tracheal system through spiracles
  2. air moves into the tracheae made up of chitin which prevents it from collapsing and diffuses into the tracheoles
  3. oxygen diffuses in water in tracheal fluid and diffuses down concentration gradient into body cells
  4. carbon dioxide diffuses down concentration gradient out of the body into tracheoles
  5. air is carried back to spiracles via tracheae and released from body
• Lactic acid accumulation:

  1. lactic acid accumulation reduces the water potential in tracheal fluid at the end of the tracheoles
  2. water leaves the tracheoles via osomosis
  3. a higher surface area is exposed for gaseous exchange
• Three main parts of an insect:

  • head
  • thorax
  • abdomen
• gills:

  • covered by an operculum flap
  • consist of stacked filaments containing lamellae
  • lamellae surrounded by extensive blood vessels