Question

Term used in blood flow and water in fish in opposite direction across the gills

Answer 1

Gills are tissues which consist of threadlike structures called filaments. ... Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange.

Fish physiology - Wikipedia

Answer 2

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The arrangement of water flowing past the gills in the opposite direction to the blood (called countercurrent flow) means that they can extract oxygen at 3 times the rate a human can.

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