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Liver cells are about 100 billion. It constitutes 80% of the Liver cell population. They have a polyhedral appearance, with six or more faces, variable in shape and size, with an average diameter of 20-30 microns and a volume of about 5000 cubic microns. They are anastomosed with each other in monocellular layers and are located in the path of the sinuses and form the hepatic lobule – at the peripheral level of the lobule, at the level of the portobiliary space and under the capsule of Gleason – a limiting layer that deals with the surrounding connective tissue. has it. The shape and volume of hepatocytes vary depending on age, location in the lobule, and regeneration activity. In relation to receiving solutes, the membrane movement of water can increase the cell volume by 5%.

What Is The Function Of Liver Cells

The hepatocyte has a triple polarity consisting of three different domains that are located on the different sides that the cell presents: the sinus or vascular pole, facing the sinus and the subendothelial space (dis space). Biliary duct or pole, which defines thin ducts (secretory capillaries) that bend between two adjacent liver cells. A side, in which the intercellular spaces do not communicate with the bile ducts. The sinus domain or vascular pole constitutes from 37 to 70% of the cell surface. In these areas, the cell surface is covered by 25-50 microvilli per micron/square, up to 0.5 µm long and 0.1 µm in diameter. Numerous microvilli in the subendothelial space (perisinusoidal space) project towards the cushions of endothelial cells.

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The vascular pole also has numerous small vesicles from pinocytosis, bulbous depressions and protrusions that are characteristic of exocytosis as well as selective endocytosis. Ultrastructural studies under the scanning electron microscope have shown that dys spaces are not limited to the subendothelial area, but spread between adjacent liver cells and form narrow and irregular depressions. In all these spaces, both perisinusoidal and subendothelial, the surfaces of liver cells are rich in microvilli. Thus, an extensive microlabyrinthine system of perivascular and intercellular spaces is created, where blood plasma circulates freely, thus enabling intense and direct exchanges between the blood and the vascular pole of hepatocytes. The fluid resulting from such exchanges with high metabolic activity, on the one hand, is placed inside the blood circulation, on the other hand, it flows inside the disc spaces, is transferred to the edge of the lobule, and in the space enclosed by numerous fibers. is being poured Collagen in the peripheral surface of the portal spaces (spaces). The fluids in the spaces of Disse and Mail are not lymphatic in the strict sense, but should be considered as interstitial fluids that contribute to the formation of true lymph, which is formed on the surface of lymphatic vessels formed with their walls. It is located, in close contact with the post spaces in the Portobiliare area.

Canalicular domain; or bile pole, constitutes 13-15% of the cell surface. The cellular surfaces used to delimit the bile ducts are flat and tightly closed, except for a small area where the surface appears to be sunken. This, along with a similar indentation in the adjacent cell wall, bounds the wall of the bile duct. The diameter of the channels varies from 0.5 microns in the pericentral region to 2.5 microns in the periportal region. The hepatocyte surfaces that bound the bile duct have numerous short microvilli that protrude into the lumen and are separated from the adjacent intercellular spaces by junctional complexes (occluded zones). Cytoplasmic channels that form bile ducts. They can be considered as true intracellular roots of bile ducts.

The lateral domain extends between the margins of the channels to the vasculature, from which it is separated from the junctional complexes, and constitutes the remaining 15-50% of the surface with the role of connection and communication between hepatocytes. Under normal conditions, no connection is possible between the biliary pole closed by binding complexes and the vascular pole of the hepatocyte. Therefore, adjacent surfaces of the same hepatocyte can simultaneously engage in very different absorptive and secretory functions. In general, the cell surfaces that target the perivascular spaces are much wider than those that line the bile ducts. This is consistent with the greater metabolic commitment that the hepatocyte makes at the level of the sinusoidal domain (absorption and increase in circulating blood flow) compared to the biliary (excretion).

In the cytosol of liver cells, there is a three-month dynamic network of cytoskeletal elements. Microfilaments, positive for actin reaction, are mainly located around the bile capillaries involved in channel motility. Regarding intermediate strands, it is important to note that K18 is a cytokeratin expressed in hepatocytes: a K18 mutation is associated with cryptogenic liver cirrhosis. Microtubules, which are essential for maintaining cell shape as well as for vesicular transport and mitosis, are positive for tubulin. It should be noted that K19 expression, which is present in many simple epithelial tissues including bile ducts, is not present in mature hepatocytes and thus characterizes bile duct cells. The nucleus of hepatocytes is usually very bulky and spherical, contains one or more conspicuous nucleoli, and constitutes 5-10% of the cell volume. 20% of hepatocytes are binucleated and about 15% have a tetraploid kit. Under normal conditions, mature liver cells rarely enter mitosis. However, in regeneration processes, mitosis can be multiple.

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Organelles have a relatively precise cytoplasmic location that is associated with specific cellular functions. The endoplasmic reticulum (REL) is presented in both smooth and wrinkled forms, while free ribosomes (polyribosomes) are also abundantly distributed in the cytoplasm. The number and extent of channels and reservoirs of hepatocyte endoplasmic reticulum are subject to continuous changes, which indicate the dynamic functional involvement of different organs. The endoplasmic reticulum constitutes 15% of the cell volume and its surface is 35 times more than the surface of the plasma membrane. Rough endoplasmic reticulum (RER) predominates over smooth reticulum (REL). The relationship between these two types differs according to the physiological state and the location of hepatocytes in the grape: the smooth network area is twice as large in region 3 compared to region 1 of the berry. Ligand parenchymal cells are grouped in concentric zones in the center of the portal space, zone 1 being the most proximal, while zones 2 and 3 are more distal to the afferent blood vessels. Oxygen tension and blood nutrient levels decrease from zone 1 to zone 3. Thus, zone 1 hepatocytes are the first to receive oxygenated blood and the last to be affected by necrosis. Zones 2 and 3 receive blood with an oxygen and nutrient content that is highly vulnerable to hepatotoxicity and hypoxic damage (see Hepatic Circulation).

A precise topographic relationship between glycogen inclusions and smooth endoplasmic reticulum membranes was observed. Such membranes with their enzyme kit (glucose-6-phosphatase) can help the process of glycogenolysis and the subsequent entry of glucose into the blood. In addition, lipids absorbed by the blood are transported through the vascular pole of the hepatocyte to the smooth endoplasmic reticulum, whose membrane is part of the enzymes responsible for cholesterol synthesis and degradation of many lipid-soluble drugs (such as barbiturates). . Granular endoplasmic reticulum and free ribosomes are responsible for the synthesis of plasma proteins that are produced by the liver and circulate through the vascular pole of hepatocytes (albumin, fibrinogen). The endoplasmic reticulum of hepatocytes also plays an important role in the assembly of lipoprotein molecules: at the vascular pole, hepatocytes without hepatocytes, in the space of Disse, particles called VLDL (very low density lipoprotein) that already appear inside smooth tubules. Endoplasmic reticulum, close to the vascular pole. Hepatocyte hydration (cell volume) is dynamic and can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such volume changes were identified as a novel and important modulator of cell function. This provides an early example for the interaction between a physical parameter (cell volume) on the one hand and metabolism, transport, and gene expression on the other. Such events include mechanotransduction (osmosensing), which triggers signaling cascades toward liver function (osmosensing). This paper reviews our own work on this topic with an emphasis on the role of β

Hepatocyte volume can change within minutes under the influence of nutrients, hormones, and toxins due to the creation or loss of osmotic gradients and corresponding water fluxes across the plasma membrane (for reviews, see Graff and Hausinger 1996; Hausinger 1996a,b). Although hepatocytes, like any cell type,

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