<prompt> Counter current mechanism, all are true exceptOccurs due to opp flow in vasa recta and loop of henleSeen in medullary nephronHelps in creating osmolarity gradientUrea has no role  <response>: Countercurrent mechanism, a system in the renal medulla that facilitates concentration of the urine as it passes through the renal tubules, were medullary osmolarity created by urea.Ref: Ganong;s review of medical physiology; 24th edition; page no; 687 