chapter 18 Digestive System III: Liver, Gallbladder, and Pancreas LIVE R 639 hilum of the liver). About 80% of the hepatic lymph follows this pathway and drains into the thoracic duct, forming the major portion of the thoracic duct lymph.
Hepatocytes make up the anastomosing cell plates of the liver lobule.
Hepatocytes are large, polygonal cells measuring between 20 and 30 m in each dimension. They constitute about 80% of the cell population of the liver.
Hepatocyte nuclei are large and spherical and occupy the center of the cell. Many cells in the adult liver are binucleate; most cells in the adult liver are tetraploid (i.e., they contain the 4d amount of DNA). Heterochromatin is present as scattered clumps in the nucleoplasm and as a distinct band under the nuclear envelope. Two or more well-developed nucleoli are present in each nucleus.
Hepatocytes are relatively long-lived for cells associated with the digestive system; their average lifespan is about 5 months. In addition, liver cells are capable of considerable regeneration when liver substance is lost to hepatotoxic processes, disease, or surgery.
The hepatocyte cytoplasm is generally acidophilic. Specific cytoplasmic components may be identified by routine and special staining procedures, including  basophilic regions that represent rough endoplasmic retic ulum (rER) and free ribosomes.  numerous mitochondria; as many as 800 to 1,000 mito enzyme histochemistry.
 multiple small Golgi complexes seen in each cell after specific staining. large numbers of peroxisomes demonstrated by immunocytochemistry.
 deposits of glycogen stained by means of the periodic acid–Schiff (PAS) procedure. However, in a well-preserved hematoxylin and eosin (H&E) preparation, glycogen is also visible as irregular spaces, usually giving a fine foamy appearance to the cytoplasm.
 lipid droplets of various sizes seen after appropriate fixation and Sudan or toluidine blue staining (Plate 66, page 658). In routinely prepared histologic sections, round spaces are sometimes seen that represent dissolved lipid droplets. The number of lipid droplets increases after injection or ingestion of certain hepatotoxins, including ethanol.
 lipofuscin pigment within lysosomes seen with routine H&E staining in various amounts. Well-delineated brown granules can also be visualized by the PAS method.
As noted previously, the hepatocyte is polyhedral; for convenience, it is described as having six surfaces, although there may be more. A schematic section of a cuboidal hepatocyte is shown in Figure 18.11. Two of its surfaces face the perisinusoidal space. The plasma membrane of two surfaces faces a neighbo ring hepatocyte and a bile canaliculus. Assuming that the cell is cuboidal, the remaining two surfaces, which cannot be seen in the diagram, would also face neighboring cells and bile canaliculi. The surfaces that face the perisinusoidal space correspond to the basal surface of other epithelial cells; the surfaces that face neighboring cells and bile canaliculi correspond to the late ral and apical surfaces, respectively, of other epithelial cells.
FIGURE 18.11 • Schematic diagram of a plate of hepatocytes interposed between hepatic sinusoids. This diagram shows a one-cell-thick plate of hepatocytes interposed between two sinusoids. If it is assumed that the cell is cuboidal, two sides of each cell (shown) would face hepatic sinusoids, two sides of each cell (shown) would face bile canaliculi, and the additional two sides (not shown) would face bile canaliculi. Note the location and features of a hepatic stellate cell (Ito cell) filled with cytoplasmic vacuoles containing vitamin