Countercurrent exchange in the small intestine.
D000818:Animals; D001692:Biological Transport; D002247:Carbon Isotopes; D002415:Cats; D007413:Intestinal Mucosa / Q000098:blood supply*; D007421:Intestine, Small / Q000098:blood supply*; D007726:Krypton; D011868:Radioisotopes; D012413:Rubidium
D002247:Carbon Isotopes; D011868:Radioisotopes; D007726:Krypton; D012413:Rubidium