Evidence for the existence of a countercurrent exchanger in the small intestine in man.
The vasculature in the human villus forms vascular loops by the supplying arterial vessel and the draining capillaries and/or veins. This study reports two experimental observations that strongly suggest that these vascular loops function as countercurrent exchangers. (1) The elimination of intraarterially injected 85Kr from the human small bowel exhibits an initial very rapid component of the type earlier reported in the feline gut. This component in all probability reflects the extravascular "shunting" in the exchanger of the injected radioactive tracer. (2) When exposing the intestinal mucosa to an isotonic electrolyte solution containing glucose, an osmolality gradient from the tip to the base of the human villi was demonstrated, the tips having an osmolality of around 700 milliosmoles per kg H2O. This hyperosmolality is created by the exchanger acting as a countercurrent multiplier.
D003106:Colon / Q000098:blood supply / Q000378:metabolism; D004573:Electrolytes / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000098:blood supply / Q000378:metabolism* / Q000648:ultrastructure; D007421:Intestine, Small / Q000098:blood supply / Q000378:metabolism*; D009994:Osmolar Concentration; D012039:Regional Blood Flow
D004573:Electrolytes