Blood flow and absorption from the rumen.

Blood flow to the ruminoreticular epithelium varies cyclically with feeding. Within this range the absorption of rapidly penetrating solutes will be dependent on the blood flow. For HTO absorption, the most satisfactory model suggests the involvement of a countercurrent exchanger behind the epithelium. The consequences of this arrangement are presented, and are qualitatively consistent with known effects of solute absorption on net water movement. The control mechanisms for net water absorption are not fully identified. The observed blood flows in the splanchnic region raise interesting questions of functional changes in the omasum and fat.