Hepatocytes are the characteristic cells of the liver, to the point of making up 80% of the hepatic volume and 60% of all cells in the organ. In addition to composing the main mass of the liver, hepatocytes also represent the most active and functional part of the organ, as evidenced by their histological characteristics.
By examining a hepatocyte under an electron microscope, we can in fact note the following characteristics:
- polyhedral shape, with 5-12 surfaces and 20-30 µm in diameter;
- spherical, euchromatic and often tetraploid, polyploid or multiple nucleus (two or more nuclei, up to four per cell);
- presence of an abundant endoplasmic reticulum, both rough and smooth;
- abundance of mitochondria, lysosomes and the Golgi apparatus;
- glycogen granules and lipid vacuoles often very evident, present in varying numbers and sizes depending on the nutritional status and the digestion phase;
- numerous and large peroxisomes;
- abundance of vacuoles containing enzymes, such as urease in crystalline form;
- presence of vacuoles containing ferritin and hemosiderin crystals.
The faces of the hepatocytes are in close contact with each other and, on one side (on one side) delimit the biliary capillaries, on the other they look towards the sinusoidal walls:
- the plasma membrane facing the hepatic sinusoids (blood vessels) has numerous irregularly shaped microvilli, which amplify the possibility of metabolic exchanges between blood and hepatocytes; there are also small vesicles of pinocytosis;
- in the plasma membranes of adjacent hepatocytes, microscopic channels where bile flows (biliary canaliculi) are formed by joining curves adjacent to the shower. In fact, near the lumen of these canaliculi the vesicles of the hepatocyte are collected in order to pour the various components of the bile into them. Together these canaliculi give rise to the biliary tree.
- In the other sites, the various hepatocytes are connected by numerous junction complexes (gap junctions and desmosomes); Liver cells are joined by these tight junctions to prevent bile from infiltrating the intercellular spaces, remaining well confined to the canalicular system (bile is toxic to hepatocytes).
Naturally, the richness of organelles that characterizes the hepatocyte is an indication of the enormous variety of biosynthetic and degradative activities performed by the organ.From the point of view of liver physiology, hepatocytes play a central role in:
- glucose, lipid and protein metabolism
- bilirubin metabolism and bile production
- detoxification metabolism of endogenous (bilirubin, hormones) and exogenous (drugs) compounds
and in:
- plasma protein synthesis (transport)
- synthesis of all coagulation factors (except VIII-vWF) vit K dependent (2nd, 7th, 9th, 10th)
- glycogen deposit, vit. B12, vit. A, D, E, K
