[Campbell Biology P.935] Which of the following is the most crucial feature enabling the hig... | Practice Question

Which of the following is the most crucial feature enabling the high efficiency of a countercurrent heat exchanger in animals?

  • A: Arteries and veins being of the same diameter.
  • B: Blood flowing in the same direction in adjacent arteries and veins.
  • C: Heat transfer occurring only at the very end of the extremity.
  • D: Arteries and veins being in close contact with blood flowing in opposite directions.

Explanation

The high efficiency of countercurrent heat exchangers relies on two critical factors: the close proximity of arteries and veins, and the blood flowing in opposite directions. This arrangement allows for continuous heat transfer along the entire length of the vessels, maximizing heat retention.