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

The liver is an extremely important organ in our species and in the rest of vertebrates. This structure, in humans, 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 second only to the heart (the figure rises to 5,000 milliliters per minute). The functions of this organ, as we will see in later lines, 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 make it up? Today we approach the world of hepatocytes, the cells that predominate in liver tissue and shape this essential organ for life.

• Related article: "Main Cell Types of the Human Body"

Hepatocytes: cells of essential function

First of all, it is of special interest to know that hepatocytes make up 80% of the liver and form its parenchyma, that is, the tissue specialized in the functions that define the organ. Before going into morphological and functional issues, we review the functions of the liver (and therefore the hepatocytes) in a few lines. Go for it:

• Bile production: Although it is stored in the gallbladder, this breakdown substance is synthesized in the liver.
• Production of certain blood proteins and cholesterol, an important hormone precursor 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, hemoprotein essential for the transport of oxygen to the different organs of the body.

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

Hepatocyte Morphology

Once we have described in a general way the functions of the liver and I have shown you some interesting statistics to frame it 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 the hepatocytes.

First of all, it is interesting to know that these cells are polyhedral or prismatic in nature, that is, they have a geometric shape with several faces (usually 6). These individual structures are observed with a light 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 to 25% of the cell. In addition, these are tetraploid, that is, they have 4 sets of chromosomes enclosed in the nucleus. (instead of 2, as is the case with most cells in the human body, naturally diploid).

As far as the cytoplasm is concerned (part of the cell that surrounds the nucleus and is delimited by the outer membrane), it stands out the fact that contains glycogen and fat inclusions, data that is clearly justified by the storage function performed by 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 liver cell surface in mammals. Undoubtedly, this evidences the great metabolic expense and work that the hepatocytes must face.

• You may be interested in: "Hepatitis: what it is, types, symptoms and treatments"

How are they organized?

Without going fully 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 venule. liver, while the bile canaliculi allow the excretion and transport of bile from the bile ducts. hepatocytes. Thus, this polarity is essential for the correct functioning of the cells that concern us here.

Unlike other epithelial cells, this specialized type is not attached to a membrane. basal, but rather the cell is surrounded by an extracellular matrix secreted by the cell itself. hepatocyte. These "spaces" facilitate the exchange with the sinusoidal channels already named, because through them, these cells capture water, electrolytes, solutes dissolved organics in the blood plasma (such as bile acids) or drugs, which are metabolized and eliminated from the canalicular pole or bile. Thanks to this little histological lesson we can understand how the liver is capable of purifying blood.

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

Functions of the hepatocytes

We abandon the histological subject, since there are some complex concepts to cover that, unfortunately, would be somewhat beyond the scope of this space. Even so, we believe that this previous summary allows us to get a general idea of ​​the functioning and disposition of hepatocytes.

As you may have guessed before, the main function of this cell type is to metabolize substances that are the product of food digestion. This is possible because hepatocytes are supplied (at the sinusoidal pole) by the portal veins, which collect the compounds resulting from the digestion of food at the intestinal level. This involves, at the cellular level, the synthesis and storage of proteins, the metabolism of carbohydrates, the metabolism of lipids and gluconeogenesis, that is, 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 said in previous lines, these cells have a catabolic function (degradation) of drugs and other toxic compounds and the synthesis and transport of bile to the gallbladder, an essential liquid in the digestion process.

The importance of hepatocytes and the liver

You only need 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 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 the tissue level, giving the patient the characteristic yellow skin tone. This symptom is usually accompanied by swollen legs and abdomen, changes in the color of stool and urine, and great ease in showing superficial bruises.

Addictions such as chronic alcoholism can favor the appearance of all these signs, since cirrhosis is nothing more than the replacement of natural liver tissue by fibrous scar tissue. Of course, the tips and considerations to avoid liver upset are self-explanatory: the more we expose our body to harmful substances, the purification system that allows us to be alive.

Summary

Who would have told us that such a specific cell type would give us so much to talk about? hepatocytes They are not only the essential component of the liver at a structural level, but also synthesize bile, metabolize products from the diet and are capable of breaking down 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, since the World Health Organization (WHO) estimates that more than 3 million people died in 2016 from the harmful use of alcohol, representing one in 20 deaths worldwide. world. To some extent, keeping our liver healthy is a matter of will, which is why a proper lifestyle can save our lives.

Bibliographic references:

• Liver Anatomy and Function, Stanfordchildrens.org. Collected on November 7 in https://www.stanfordchildrens.org/es/topic/default? id=anatomyandfunctionoftheliver-90-P06162
• Jaundice, Professor Juan Cabrera, course 06/07. Collected on November 7 in http://www2.ulpgc.es/hege/almacen/download/38/38483/ictericia_sindrome_de_colestasis.pdf
• My liver, dude. Collected on November 7 in https://www.amhigo.com/mi-higado#:~:text=Circulaci%C3%B3n%20del%20h%C3%ADgado&text=En%20total%20recibe%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. YO. (2017). The hepatocyte as an example of interaction between cell biology and metabolic pathways. Journal of the Faculty of Medicine (Mexico), 60(2), 52-58.
• Cell types: hepatocyte, Atlas of plant and animal histology. Collected on November 7 in https://mmegias.webs.uvigo.es/8-tipos-celulares/hepatocito.php#:~:text=Los%20hepatocitos%20son%20las,(Figuras%201%20y%202).&text=Organizaci%C3%B3n%20del%20h%C3%ADgado.