Hepatocytes: what are they and what are their functions in the human body?

Summary of the characteristics of hepatocytes, key cells for liver function.

The liver is an extremely important organ in our species and in the rest of vertebrates. This structure, in the human being, weighs about 1,800 grams, that is, 2% of the body mass of an adult individual.

With such a small weight, the liver is capable of receiving 1,500 milliliters of Blood per minute, a value only surpassed by the heart (the figure amounts to 5,000 milliliters per minute). The functions of this organ, as we shall 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 which functional units build it? Today we approach the world of hepatocytes, the cells that predominate in liver tissue. and shape this essential organ for life.

Hepatocytes: cells of essential function.

First of all, it is of special interest to know that hepatocytes account for 80% of the liver and form its parenchyma. hepatocytes make up 80% of the liver and form its parenchymai.e. the tissue specialized in the functions that define the organ. Before going into morphological and functional issues, let us review the functions of the liver (and thus the hepatocytes) in a few lines. Let's get down to it:

• Production of bile: although it is stored in the gallbladder, this decomposing substance is synthesized in the liver.
• Production of certain blood proteins and cholesterol, an important precursor of hormones and 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.
• Processing of hemoglobin, a hemoprotein essential for the transport of oxygen to the various organs of the body.

In general, all these functions and many more can be summarized in a number of key terms: synthesis, storage, metabolism and detoxification.. This is certainly one of the most multifunctional and essential organs in the whole body.

Morphology of hepatocytes

Once we have described in a general way the functions of the liver and we have shown you some interesting statistics to frame it from a physiological point of view, it is time to get 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 with an optical microscope, as they are large, about 20-40 micrometers in diameter.

It is also characteristic of this cell type to present two spherical nuclei, which occupy 20-25% of the cell. In addition, they are tetraploid, i.e., they have 4 sets of chromosomes enclosed in the nucleus (instead of 2, as is the case in most cells of the human body, which are diploid in nature).

As far as the cytoplasm is concerned (the part of the cell that surrounds the nucleus and is delimited by the outer membrane), it is noteworthy that it has inclusions of glycogen and fatThis is clearly justified by the storage function of the liver.

It should also be noted that on this medium there are abundant mitochondria of small size (about 800 to 1,000 per cell), which occupies up to 25% of the hepatic cell surface in mammals. Undoubtedly, this is evidence of the great metabolic expense and work that hepatocytes must face.

How are they organized?

Without getting into complex histological terms, we can say that these cell types are polarized, that is, they have two poles, one sinusoidal and the other canalicular. The sinusoids are channels through which blood flows from the portal spaces to the hepatic venule, while the biliary canaliculi allow the excretion and transport of bile from the hepatocytes. Thus, this polarity is essential for the correct functioning of the cells we are concerned with 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 mentioned, because through them, these cells capture water, electrolytes, organic solutes dissolved in the blood plasma (such as bile acids) or drugs, which are metabolized and eliminated from the canalicular or biliary pole. Thanks to this small histological lesson we can understand how the liver is able to purify the blood.

It should be noted that, once bile is produced in the hepatocytes, it flows into the intrahepatic bile ducts, which ultimately meet in a common hepatic duct, which carries the substance to the gallbladder, where it is stored. As in many other transport structures, we must imagine this series of canals and tubes as a treeThe cells could be the analogue of leaves, and each of the individual branches, the small ducts leading to the main trunk, in this case the common hepatic duct.

Functions of hepatocytes

We leave the histological subject matter, as there are some complex concepts to be covered that, unfortunately, would be somewhat beyond the competencies of this space. Even so, we believe that this previous summary allows us to get a general idea of the function and arrangement of the hepatocytes.

As you may have guessed beforehand, the main function of this cell type is to metabolize substances that are the product of food digestion. This is possible because the hepatocytes are irrigated (at the sinusoidal pole) by the portal veins, which collect the compounds resulting from the digestion of food.which collect the compounds resulting from the digestion of food at the intestinal level. This involves, at the cellular level, protein synthesis and storage, carbohydrate metabolism, lipid metabolism and gluconeogenesis, i.e. the formation of glucose from precursors that are not carbohydrates (such as lactate, pyruvate or glycerol).

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

The importance of hepatocytes and the liver

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

When hepatocytes are destroyed or their ducts fail, an increase in bilirubin is generated at tissue level, which gives the patient the characteristic yellow skin tone. This symptom is often accompanied by swollen legs and abdomen, changes in the color of stool and urine and a great facility in showing superficial bruises.

Addictions such as chronic alcoholism can favor 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 body to harmful substances, the more the purifying system that allows us to stay alive will suffer.

Summary

Who knew that such a specific cell type would give us so much to talk about? Hepatocytes are not only the essential structural component of the liver, but also synthesize bile, metabolize dietary products and are capable of degrading drugs and other harmful substances in the bloodstream. and are capable of degrading drugs and other harmful substances present in the bloodstream.

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

Bibliographic references:

• Anatomy and function of the liver, Stanfordchildrens.org. Collected on November 7 at https://www.stanfordchildrens.org/es/topic/default?id=anatomyandfunctionoftheliver-90-P06162.
• Jaundice, Professor Juan Cabrera, course 06/07. Retrieved November 7 at http://www2.ulpgc.es/hege/almacen/download/38/38483/ictericia_sindrome_de_colestasis.pdf.
• My liver, my friend. Retrieved November 7 from https://www.amhigo.com/mi-higado#:~:text=Circulaci%C3%B3n%20del%20h%C3%ADgado&text=In%20total%20receives%201%2C500%20mL,directly%20from%20the%20artery%20aorta.
• Rojas Lemus, M., Milán Chávez, R., Delgado Medina, A., Bizarro Nevares, P., Cano Gutiérrez, G., Cafaggi Padilla, D., ... & Fortoul van der Goes, T. I. (2017). The hepatocyte as an example of interaction between cell biology and metabolic pathways. Revista de la Facultad de Medicina (Mexico), 60(2), 52-58.
• Cell types: hepatocyte, Atlas of plant and animal histology. Retrieved November 7 from https://mmegias.webs.uvigo.es/8-tipos-celulares/hepatocito.php#:~:text=The%20hepatocytes%20are%20the,(Figures%201%20and%202).&text=Organization%C3%B3n%20of%20h%C3%ADgado.