Index
They are the most abundant type of cell in the human liver.
A hepatocyte is a cell of the central parenchymal tissue of the liver. Hepatocytes make up 70-85% of the liver mass. These cells are involved in:
- Protein synthesis.
- Protein storage.
- Transformation of carbohydrates.
- Synthesis of cholesterol, bile salts, and phospholipids.
- Detoxification, modification, and excretion of exogenous and endogenous substances.
- Start of bile formation and secretion.
- Chemically process the molecules usually found in the body, such as hormones, as well as foreign substances such as medicines and alcohol.
Structure
The typical hepatocyte is cubic with sides of 20-30 μm (in comparison, a human hair has a diameter of 17 to 180 μm). The specific volume of a hepatocyte is 3.4 x 10-9 cm3.
The smooth endoplasmic reticulum is abundant in the hepatocytes, while most of the cells in the body have small amounts.
Micro anatomy
The hepatocytes show an eosinophilic cytoplasm that reflects numerous mitochondria and dotted basophils due to large amounts of rough endoplasmic reticulum and free ribosomes.
Brown lipofuscin granules are also seen (as age increases) and irregular areas of unstained cytoplasm; These correspond to glycogen and cytoplasmic lipid reserves during histological preparation.
The average life of the hepatocyte is five months; they can regenerate
The nuclei of the hepatocytes are round with scattered chromatin and prominent nucleoli.
Anicocariosis (or variation in the size of nuclei) is common and often reflects tetraploidy and other degrees of polyploidy, a regular feature of 30-40% of hepatocytes in adult human liver. Binucleated cells are also standard.
The hepatocytes are organized in plates separated by vascular channels (sinusoids), an arrangement supported by a network of reticulin (collagen type III).
Hepatocyte plaques are one cell thick in mammals and two in chickens. The sinusoids show a discontinuous and fenestrated endothelial cell lining.
The endothelial cells do not have a basement membrane. They are separated from the hepatocytes by the space of Disse, which drains the lymph into the lymphatic vessels of the portal tract.
The Kupffer cells are scattered between endothelial cells; they are part of the reticuloendothelial system and the erythrocytes consumed by phagocytosis.
Stellate (Ito) cells store vitamin A and produce extracellular matrix and collagen; They are also distributed among endothelial cells, but they are difficult to visualize by optical microscopy.
Functions
Protein synthesis: The hepatocyte is a cell in the body that makes serum albumin, fibrinogen, and the group of prothrombin clotting factors (except factors 3 and 4).
It is the leading site for synthesizing lipoproteins, ceruloplasmin, transferrin, complement, and glycoproteins. Hepatocytes make their structural proteins and intracellular enzymes.
Protein synthesis is performed by the rough endoplasmic reticulum (RER), and both the wild and smooth endoplasmic reticulum (SER) participate in the secretion of the proteins formed.
The endoplasmic reticulum (ER) is involved in conjugating proteins with lipid and carbohydrate residues synthesized by or modified within hepatocytes.
Metabolism of carbohydrates: The liver forms fatty acids from carbohydrates and synthesizes triglycerides from fatty acids and glycerol. Hepatocytes also synthesize apoproteins, with which they then assemble and export lipoproteins.
The liver is also the leading site in the body for gluconeogenesis, forming carbohydrates from precursors such as alanine, glycerol, and oxaloacetate.
Lipid metabolism: The liver receives many lipids from the systemic circulation and metabolizes the remains of chylomicrons. It also synthesizes acetate cholesterol and synthesizes bile salts even more. The liver is the only bile salt formation site.
Detoxification: Hepatocytes can metabolize, detoxify and inactivate exogenous compounds such as drugs (drug metabolism) and insecticides and endogenous compounds such as steroids.
The drainage of intestinal venous blood to the liver requires efficient detoxification of various absorbed substances to maintain homeostasis and protect the body against ingested toxins.
One of the detoxifying functions of hepatocytes is to modify the ammonia in urea for its excretion.
