Fish Respiration: Countercurrent exchange

Florece, Christine Marie C.

GILLS

Gills-main site of gas exchange in almost all fishes

-consists of bony or stiffened arches (cartilage) that anchor pairs of gill filaments

Bony Fish

Sharks and Rays Sharks have 5-7 pairs of gill slits located on the sides of their heads.

Gills of rays are organs located on either side of the head or just below the mouth.

Gill Structure

Parts and Functions Gill rakers -appendages along the front edge of the gill arch

-help make sure that no extraneous material gets into the gill filaments to clog them up Gill arches

- the actual bones or cartilage that support a particular gill

-have arteries inside them that contain blood low in oxygen, these arteries branch into smaller arterioles that run inside the filaments

Gill Filaments-hair-like structures on the gills which

absorb the oxygen from the lamellae-contain a capillary network that

provides a large surface area for exchanging oxygen and carbon dioxide

Lamellae-are very small, and they have very

thin surface for gases to diffuse through the capillary network, so oxygen can be circulated around the body to cells

Numerous lamellae protrude from both sides of each filament and are the primary sites of gas exchange.

Video

Countercurrent Exchange

This system moves water flowing across the gills, in an opposite direction to the blood flow creating the maximum efficiency of gas exchange.

 This means that the blood flows along the vessels in the lamellae in the opposite direction to which the water is passing on the outside of the lamellae.

-this method of change is capable of moving half of the oxygen content of the water to the blood-it will diffuse large amounts of oxygen

Countercurrent Exchange Water and blood flow in opposite direction

Water has more oxygen content than the blood, so oxygen diffuses to the blood

Capillaries within each lamella (gill filaments) picks up oxygen to the blood and gives off carbon dioxide and metabolic wastes like Ammonia

This maximizes the concentration gradient and speeds up diffusion

removes almost all of the oxygen (80-90%) from the water that passes over the gills and then transfers it to the blood (co-current exchange- only 50%)

The concentration of oxygen gained from this system would meet the physiological needs of the fish

Thank you.

Retrieved from: http://global.britannica.com/EBchecked/topic/208456/fish/63637/The-respiratory-system

http://www.kwic.com/~pagodavista/schoolhouse/species/fish/fishgill.htm

http://www.earthlife.net/fish/gills.html http://www.s-cool.co.uk/a-level/biology/gas-exchange/revise-it/gas-exchange-in-fish

http://www.todayifoundout.com/index.php/2011/09/how-fish-gills-work/

Video from: https://www.youtube.com/watch?v=XEIRlw5rCUk