Some animals such as fish use a countercurrent exchange system to enhance respir
ID: 205684 • Letter: S
Question
Some animals such as fish use a countercurrent exchange system to enhance respiration. Which of the following is true of the countercurrent exchange system?
It is more efficient than the parallel current system
It serves to maximize a diffusion gradient between water and oxygen
It allows diffusion to occur along the entire length of the capillary bed
It depends on elements moving in opposing directions of one another
All of these answers are true of the countercurrent system
It is more efficient than the parallel current system
It serves to maximize a diffusion gradient between water and oxygen
It allows diffusion to occur along the entire length of the capillary bed
It depends on elements moving in opposing directions of one another
All of these answers are true of the countercurrent system
Explanation / Answer
Option 5 ; All of these answers are true of the countercurrent system
In counter-current exchange system, the blood flows through the blood vessels in the opposite direction to the water flowing through the lamellae. The filaments and lamellae give gills a large surface area:volume ratio, increasing the efficiency of diffusion of gases between the water and the blood by allowing more particles to diffuse at any one time. It allows maximum oxygen to be absorbed by the blood from the water, by maintaining the concentration gradient the whole way through the gills. In counter-current exchange system all of the water passing over the gills has oxygen in it, and no water that comes in the mouth will leave without passing through the gills. This helps the efficiency of gas exchange in fish by allowing oxygen to be absorbed from all of the water that comes into the fish. If the water had to go out the same way, some water wouldn't make it to the gas exchange surface for oxygen to diffuse into the blood from it, thus it is more efficient than parallel current system.
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