Countercurrent mechanism is not seen in:
Kidney
Testes
Eye
Intestine
Ans: C. Eye(Ref Ganong 25/e p417, 420, 685, 24/e p687, 419, 422) .Countercurrent mechanism:Not seen in eye.Inflow runs parallel to, counter to & in close proximity to outflow for some distance.Seen in kidney, limbs, testis & intestine.In renal system - Both loops of Henle & vasa recta in renal medulla.Intestine - Villi where oxygen directly diffuses from aerioles to vein.