Liver: Functional Interactions Within the Intact Animal

inaccessibility of the hepatic vascu­ lar connections with the rest of the body and the extremely subtle nature of hepatic functions. By contrast, evaluation of many other organ functions is simpler; for example, the renal vascular anatomy and the accessibility of the functional end products of renal excretion permit precise functional evalua­ tion of the kidney. Hepatic and renal functional interactions with the body as a whole also may be compared. Urinary excretion of metabolites is the major, albeit not the only, essential renal function. By contrast, regulation of energy metabolism and of plasma constituents is the major function of the liver, while biliary excretory functions represent a relatively small part of the total hepatic functional interrelationshi ps. The liver occupies a central position in body metabolism. It regulates most of the concentrations of plasma constituents, removes metabolic end­ products, clears bilirubin and other hemochromo gens resulting from red cell destruction, detoxifies and conjugates abnormally occurring compounds and exogenous poisons, provides a constant source of glucose to meet energy requirements of the peripheral tissues, removes lactic, pyruvic and other organic acids and resynthesizes glucose from them, regulates amino