Liver: Classic Lobule Model
Classical Lobule Model
Historically, hepatic tissue is modeled as hexagon-shaped lobules surrounding central venules (aka, centralobular venules). The area of the lobule is bound by the peripheral portal triads.
- The liver tissue comprises rows, aka, plates, of hepatocytes radiating from the central venule
- Between the plates, sinusoids provide passage for blood and bile.
- Portal triads, aka, portal tracts, lie at the periphery, with the smaller vessels connecting them.
- Hepatocytes are epithelial cells with round nuclei; they are often binucleate, and, in some histological samples, glycogen granules are visible in the cytoplasm. The hepatocytes directly encircling the central venule are the limiting plate hepatocytes.
- Bile canaliculi facilitate bile passage between adjacent hepatocytes.
- Sinusoids run between plates of hepatocytes; are lined by fenestrated endothelial cells, which allow molecules, including bile, to pass from the tissue to the lumen;
- Kupffer cells, which are macrophages that remove expired red blood cells and other debris, are also present in sinusoid lining.
- Reticular fibers also line the sinusoids and form a supporting network for the liver tissues.
- Bile flows towards the peripheral portal triad, enter hepatic ducts and exit the liver.
- Arterial and venous blood flows towards the central venule; Filtered, deoxygenated blood drains to the hepatic veins and to the inferior vena cava to re-enter general circulation.