allow backtracking Changos to the answer after suberission are prohibited wi con
ID: 267109 • Letter: A
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allow backtracking Changos to the answer after suberission are prohibited wi condinue to run if you leave the test Remaining Time: 47 seconds. Less than o min rCick Status: Click Subr?t to complete his assessment Question s What best explains why countercument exchange in the fash git is vo eficen at captiring oxygen dissored in watec and tranulening it to the water wth increasing partal pressures of oxygen across the length of te cap tary bed to·?? capdarn-h bhod hnig emapalimase hns Water with decressing partial pressures of oxygen across the length of the capillary bed ows acoss cepilaries wihh blood having increasing aital presres af cron deside watar with increasing partal pessures of orygen across the large, ore. capdary bed Son aplares with hkod hrm, der,wing-stem dato Wster with decreasing partial pressures of axygn acroes the lergn of thw capltary bed hows across capilaries weilth bfood hving decreasing ef b Clck Submit to compiete bi asstExplanation / Answer
We know that n a mixture of gases, each gas has a partial pressure which is the hypothetical pressure of that gas if it alone occupied the entire volume of the original mixture at the same temperature.
The correct option is option 3 which states that water with increasing partial pressure of oxygen in the capillary bed flows across cpaillaried with blood having decreasing partial pressure of carbon dioxide. Therefore, a countercurrent exchange is mimicked int he fish gills. It is known that in case of the partial pressure of the gas in contact with water - gas moves from high to low pressure. Similary, in fish gills, oxygen is able to continually diffuse down its gradient into the blood, and the carbon dioxide down its gradient into the water.
As the blood enters the gill capillary, it encounters water that is completing its passage through the gill. Depleted of much of its dissolved oxygen, the water has a higher pO2 than the incoming blood, and O2 transfer takes place. As the blood continues its passage, its pO2 steadily increases, but so does that of the fresh, new water it encounters, since each successive position in the blood's travel corresponds to an earlier position in the water's passage over the gills. Thus, a partial pressure gradient favouring diffusion of O2 from water to blood exists along the entire length of the capillary where the partial pressure of carbon dioxide keeps decreasing as the partial pressure of oxygen keeps increasing in the blood.
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