gas exchange in fish

• gas exchange in fish

  there is a lower concentration of oxygen in water than air so fish have special adaptations to get enough of it

  in a fish, the gaseous exchange surface is the gills
• gas exchange in fish - gills

  water, containing oxygen enters the fish through it's mouth and passes out through the gills

  each gill is made of lots of thin plates called gill filaments or primary lamellae which give a big surface area for exchange of gases

  the gills are covered in lots of tiny structures called gill plates or secondary lamellae increasing surface area even more

  each gill is supported by a gill arch, the gill plates have a lots of blood capillaries and a thin surface layer of cells to speed up diffusion of oxygen
• gas exchange in fish - counter-current system

  blood flows through the gill plates in one direction and water flows over in the opposite direction

  means that water with a relatively high oxygen concentration always flows next to blood with a lower concentration of oxygen

  means a steep concentration gradient is maintained
• ventilation in fish - bony fish

  1. fish opens it's mouth which lowers the floor of the buccal cavity
  2. the volume of the buccal cavity increases, decreasing the pressure inside the cavity
  3. water is then sucked into the cavity
  4. when the fish closes it's mouth the buccal cavity is raised again
  5. decreasing the volume and increasing the pressure
  6. water is forced out the cavity across the gill filaments
  7. each gill is covered by a bony flap called the operculum (which protects gills) the increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills