Hepatocytes: what they are and what functions they have in the human body

The liver is a very important organ in our species and in other vertebrates. This structure, in humans, weighs about 1800 grams, or 2% of the body mass of an adult individual.

With such a low weight, the liver is able to receive 1,500 milliliters of blood per minute, a value only exceeded by the heart (the figure rises to 5,000 milliliters per minute). The functions of this organ, as we will see later, are essential for the physiological well-being of the organism and the persistence of the species over time.

We all know the importance of the liver, but do you know what functional units build it? Today we approach the world of hepatocytes, the predominant cells in liver tissue and give shape to this organ essential to life.

    Hepatocytes: cells with essential functions

    First of all, it is particularly interesting to know that hepatocytes make up 80% of the liver and form its parenchymaIn other words, the tissue has specialized in the functions that define the organ. Before entering into the morphological and functional issues, we review the functions of the liver (and therefore hepatocytes) in a few lines. Let’s go to this:

    • Bile production: Although stored in the gallbladder, this decaying substance is synthesized in the liver.
    • Production of certain blood proteins and cholesterol, an important precursor of hormones and a functional unit in cell membranes.
    • Purification of drugs, harmful substances and transformation of harmful ammonia into urea.
    • Production, storage and release of glucose in the form of glycogen.
    • Treatment of hemoglobin, a hemoprotein essential for the transport of oxygen to various organs of the body.

    In general, all of these functions and many more can be summarized in a number of key terms: synthesis, storage, metabolism and detoxification. Of course, we are dealing with one of the most multifunctional and essential organs in the whole body.

    Morphology of hepatocytes

    Once we have described the functions of the liver in general and have shown you some interesting statistics to frame from a physiological point of view, it is time to get hold of a scalpel and a microscope, in order to analyze the characteristic morphology of hepatocytes. .

    First of all, it is interesting to know that these cells are polyhedral or prismatic in nature, i.e. they have a geometric shape with several faces (usually 6). These individual structures are observed under a light microscope because they are large, about 20 to 40 microns in diameter.

    It is also characteristic of this type of cell to have two spherical nuclei, which occupy 20 to 25% of the cell. In addition, they are tetraploids, that is, they have 4 sets of closed chromosomes in the nucleus (instead of 2, as is the case with most cells in the human body, by nature diploid).

    With regard to the cytoplasm (part of the cell that surrounds the nucleus and is bounded by the outer membrane), the fact that has glycogen and fat inclusions, Data clearly justified by the storage function provided by the liver.

    It should also be noted that on this medium are abundant small mitochondria (approximately 800 to 1000 per cell), which occupy up to 25% of the surface of hepatic cells in mammals. Without a doubt, this testifies to the great metabolic expenditure and the work that the hepatocytes have to face.

      How are they organized?

      Without going completely into complex histological terms, we can say that these cell types are polarized, that is, they have two poles, a sinusoidal and a canalicular. The sinusoids are channels through which blood circulates from the portal spaces to the hepatic venule, while the bile ducts allow the excretion and transport of bile from the hepatocytes. Thus, this polarity is essential for the proper functioning of the cells that belong to us here.

      Unlike other epithelial cells, this specialized type is not anchored to a basement membrane, but the cell is surrounded by an extracellular matrix secreted by the hepatocyte itself. These “spaces” facilitate the exchange with the sinusoidal channels already named, because through them, these cells capture water, electrolytes, organic solutes dissolved in blood plasma (such as bile acids) or drugs, which are metabolized and eliminated from the canalicular or biliary. pole. Thanks to this little lesson in histology, we can understand how the liver is able to purify the blood.

      It should be noted that, once the bile is produced in the hepatocytes, it flows into the intrahepatic bile ducts, which eventually join in a common hepatic duct, which carries the substance to the gallbladder, where it is stored. . As in many other transport structures, you have to imagine this series of canals and pipes like a tree: The cells could be the analogue of the leaves, and of each of the individual branches, the small ducts that lead to the main trunk, in this case the common hepatic duct.

      Functions of hepatocytes

      We abandon the histological question, because there are complex concepts to cover which, unfortunately, would somewhat escape the competence of this space. However, we believe that this previous summary allows us to get a general idea of ​​how hepatocytes are functioning and arranged.

      As you may have guessed earlier, the main function of this type of cell is to metabolize the substances which are the product of the digestion of food. This is possible because the hepatocytes are irrigated (at the sinusoidal pole) by the portal vein, Which collect compounds from the digestion of food at the intestinal level. At the cellular level, these are the synthesis and storage of proteins, the metabolism of carbohydrates, the metabolism of lipids and gluconeogenesis, that is, the formation of glucose from non-carbohydrate precursors ( such as lactate, pyruvate or glycerol).

      On the other hand and as we said in the previous lines, these cells have a catabolic (degradation) function of drugs and other toxic compounds and the synthesis and transport of bile to the gallbladder, An essential fluid in the digestion process.

      The importance of hepatocytes and the liver

      It is enough to see a patient with jaundice to realize the enormous impact that liver failure can have on the body. Bilirubin is a yellowish pigment that results from the breakdown of hemoglobin in recycled red blood cells.. This substance conjugates in the liver and becomes part of the bile and is then excreted in the duodenum, which gives color to the stool.

      When hepatocytes are destroyed or their ducts break down, an increase in bilirubin is generated in the tissues, which gives the patient the characteristic tone of yellow skin. This symptom is usually accompanied by swollen legs and abdomen, changes in the color of stool and urine, and very easy to show superficial bruising.

      Addictions such as chronic alcoholism can promote the appearance of all these signs because cirrhosis is nothing more than the replacement of natural liver tissue with fibrous scar tissue. Of course, the tips and considerations for avoiding liver discomfort are self-explanatory: the more we expose our bodies to harmful substances, the more the purifying system that keeps us alive will suffer.

      summary

      Who would have thought that such a specific cell type would give us so much to talk about? hepatocytes not only are they the essential component of the liver at the structural level, but they synthesize bile, metabolize food products and are able to break down drugs and other harmful substances present in the bloodstream.

      We cannot end this space without making a sad but necessary mention of alcoholism worldwide, as the World Health Organization (WHO) estimates that more than 3 million people died in 2016 from harmful alcohol consumption, a deaths in 20 worldwide. To some extent, keeping our liver healthy is a matter of willpower, which is why a proper lifestyle can save our lives.

      Bibliographic references:

      • Anatomy and Function of the Liver, Stanfordchildrens.org. Retrieved November 7 from https://www.stanfordchildrens.org/es/topic/default?id=anatomyandfunctionoftheliver-90-P06162
      • Jaundice, Professor Juan Cabrera, course 06/07. Collected November 7 at http://www2.ulpgc.es/hege/almacen/download/38/38483/ictericia_sindrome_de_colestasis.pdf
      • My liver, amhigo. Collected November 7 at https://www.amhigo.com/mi-higado#:~:text=Circulaci%C3%B3n%20del%20h%C3%ADgado&text=En%20total%20recibe%201%2C500%20mL, directly% 20of% 20La% 20arteria% 20aorte.
      • Rojas Lemus, M., Milà Chávez, R., Delgado Medina, A., Bizarro Nevares, P., Cano Gutiérrez, G., Cafaggi Padilla, D., … and Fortoul van der Goes, TI (2017). The hepatocyte as an example of the interaction between cell biology and metabolic pathways. Journal of the Faculty of Medicine (Mexico), 60 (2), 52-58.
      • Types of cells: hepatocytes, Atlas of plant and animal histology. Collected November 7 from https://mmegias.webs.uvigo.es/8-tipos-celulares/hepatocito.php#:~:text=Los%20hepatocitos%20son%20las,(Figuras%201%20y%202). & text = Organization% C3% B3% 20del% 20h% C3% ADgado.

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