Ventilation in fish and animals

• ventilation of fish gills:

  1. mouth opens and opperculum closes which lowers the floor of the buccal cavity which increases the volume and decreases the pressure so water is sucked in
  2. mouth closes and the floor of the buccal cavity rises which decreases the volume and increases the pressure so water is forced out and through the gill filaments
  3. the opperculum (bony flap that covers gills) is forced open due to pressure, allowing water to leave the gills
• how are fish adapted for gas exchange?

  each gill is made of lots of thin branches called gill filaments (primary lamellae) which are extensions off the gill arch which then fold to make secondary lamellae, this increases the surface area.

  the gill plates have lots of blood capillaries which increases the concentration gradient and a thin surface layer of cells which provides a short diffusion pathway
• explain the countercurrent flow in fish

  blood flows through the gill plates in one direction and water flows over in the opposite direction this maintains a steep concentration gradient of oxygen between water and blood. the concentration of oxygen in the water is always higher than that in the blood, so as much oxygen diffuses from the water into the blood
• explain gas exchange in insects

  1. air enters the insects through the spiracles
  2. the spiracles connect into tracheae which branch off into smaller tracheoles
  3. the tracheoles contain a fluid which oxygen dissolves in
  4. oxygen travels through the tracheoles down the concentration gradient towards the cells, oxygen diffuses into the cells and CO2 diffuses into the tracheoles and is released out the spiracles

  insects use rhythmic abdominal movements to change the volume of their bodies to move air in and out of the spiracles, when they are flying, they use their wing movements to pump their thoraxes
• what is the ventilation method in fish called?

  countercurrent flow