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Gills are in the walls of both sides of the [[Pharynx - Anatomy & Physiology|pharynx]] and are composed of filaments which increase the surface area.
 
Gills are in the walls of both sides of the [[Pharynx - Anatomy & Physiology|pharynx]] and are composed of filaments which increase the surface area.
When a fish breaths, it takes in water into the mouth, which is then forced out through the gills.
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When a fish breaths, it takes in water into the mouth, which is then forced out through the gills. A '''countercurrent exchange''' system is in place within the gills to make gaseous exchange more efficient.
 
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A '''Countercurrent Exchange''' system is in place within the gills to make gaseous exchange more efficient.
      
==Amphibia==
 
==Amphibia==
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