fish gas exchange


Sturcture of gills

  • Fish have gills over which water continually flows
  • Gills are supported by water flowing over them so are unsutible for life on dry land
  • The water has oxygen dissolved in it

Gill arches

Gill filament

Lamella= each flament is made up of thin delicate plates containing many capillars so they look dark red

The gills are protected by an operculum

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Adaptaitions of the gills

The adaptations of the gills for efficient gas exchange are =

  • large surface area - allows more diffusion of gases
  • good blood supply - maintains concentration gradient
  • thin - short diffusion distance
  • permeable membrane - allows gases to diffuse through tissues
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Ventilation of fish gills

  • The fish opens its mouth and lowers it buccal floor increasing the volume in the mouth and decreasing the pressure
  • Water rushes in
  • The fish closes its mouth and raises it buccal floor
  • This decreases the volume and so increases the pressure in the mouth
  • Water is force over the gills and out of the operculum
  • Gas exchange happens in the gills
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This is diffusion

  • Oxygen moves from the water into the blood and carbon dioxide from the blood into the water by diffusion

Countercurrent gas exchange - concentration current is high = good rate of diffusion

The blood flow in the capilaries is the opposite to the flow of water over the gills = this means the blood is meating the new water with a full load of oxygen countercurrent exchange of water flow and blood stream maintains concentration gradients for diffusion.

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