FIG. 2.

Liver and hepatocyte physiology. (a) Cross-sectional view of the liver sinusoid. Hepatocytes are polarized such that bile acid molecules are released into bile canaliculi from the basal side while proteins are released from the apical side into sinusoidal space lined with endothelial cells. The space between the hepatocytes and the blood vessel is known as the space of Disse, where stellate cells reside. Kupffer cells can be found inside the sinusoids. Biomolecules, such as ammonia, diffuse from the bloodstream toward the hepatocytes, where they are converted into urea and secreted back toward the bloodstream. Albumin and very low-density lipids (VLDLs) are secreted from the apical side of hepatocytes into blood. (b) Zonation of liver sinusoids can be divided into three different groups of hepatocytes based on oxygen and hormonal gradients, so cells can have a specific metabolic function. (c) The hepatocytes engage multiple metabolic pathways, such as drug metabolism (phases I, II, and III), ammonia detoxification through urea cycle, production of bile salts, and glucose metabolism: gluconeogenesis and glycogenolysis in response to insulin and glucagon, respectively.