A blood alcohol concentration (BAC) or blood alcohol level (BAL) reflects the amount of alcohol in the body. Food, type and quantity of beverage, weight, sex, and rate of elimination determine the BAC after the consumption of alcohol.
The process of oxygen transfer in the gills of a fish is a good example of the benefits of countercurrent exchange. As oxygen poor blood meets an opposed flow of oxygen rich water, the oxygen begins to diffuse out of the water and into the blood stream.
Is established and maintained by the countercurrent system, and makes it possible to put out urine of variable concentration depending on the needs of the body by varying the degree of water permeability of the distal portions of the nephron.