home Audience 2 Portal vein. Topography of the portal vein. Formation of the portal vein. Portocaval anastomoses. Hepatic veins. How is the blood supply to the liver structures? Video: lecture on veins of the systemic circulation

Portal vein. Topography of the portal vein. Formation of the portal vein. Portocaval anastomoses. Hepatic veins. How is the blood supply to the liver structures? Video: lecture on veins of the systemic circulation

The general outflow of blood into the vena cava is carried out through the hepatic veins. % of all blood passes through the hepatic artery itself, the rest through the portal vein. Consequently, venous blood from the digestive tract, pancreas and spleen returns to the heart only after passing additionally through the liver. This feature of the blood circulation of the liver, called portal circulation, is associated with digestion and the performance of a barrier function.

Blood in the portal circulatory system passes through two networks of capillaries. The first network is located in the walls of the digestive organs, pancreas, and spleen; it provides the absorption, excretory and motor functions of these organs. The second network of capillaries is located directly in the liver parenchyma. It ensures its metabolic and excretory functions, preventing intoxication of the body by products formed in the digestive tract.

Research by N.V. Eck showed that if blood from the portal vein is directed directly into the vena cava, i.e. bypassing the liver, the body will be poisoned with a fatal outcome.

A feature of microcirculation in the liver is the close connection between the branches of the portal vein and the hepatic artery proper with the formation of sinusoidal capillaries in the liver lobules, to the membranes of which hepatocytes are directly adjacent. The large contact surface of blood with hepatocytes and slow blood flow in sinusoidal capillaries create optimal conditions for metabolic and synthetic processes.

In the portal circulatory system, arterial blood is under pressure mm Hg. Art. enters the first network of capillaries (for example, the intestinal wall), where it decreases to 100 mHg. Art. After passing through the second network of capillaries, already in the hepatic veins it is 0-5 mm Hg. Art. This pressure difference ensures the forward movement of blood.

Regulation of portal hemodynamics is carried out through a system of periodically contracting input and output sphincters of sinusoidal capillaries. This system adapts the blood flow to the activity of the abdominal organs, and also ensures the deposition of blood.

Rice. 8.31. Mammalian fetal circulation:

1 - aortic arch, 2 - botal duct, 3 - left pulmonary artery, 4 - pulmonary trunk, 5 - branches from the iliac arteries, passing into the umbilical ones, 6 - placental vein, carrying arterial blood, 7 - umbilical arteries from the fetal iliac artery, 8 - placenta, 9 - caudal vena cava, 10 - tract of Arans, 11 - liver, 12 - right atrium, 13 - foramen ovale in the atria, 14 - cranial vena cava

How is the blood supply to the liver structures?

The liver plays one of the main roles in metabolism. The ability to perform its functions, in particular neutralization, directly depends on how blood flows through it.

The peculiarity of the blood supply to the liver, unlike other internal organs, is that in addition to arterial blood saturated with oxygen, it also receives venous blood rich in valuable substances.

The structural unit of the liver is a lobe, which has the shape of a faceted prism, in which hepatocytes are located in rows. Each lobule is approached by a vascular triad of interlobular vein, artery and bile duct, which are also accompanied by lymphatic vessels. The blood supply to the lobules is divided into 3 channels:

Influx to the lobules.
Circulation inside the lobules.
Outflow from the hepatic lobules.

Blood sources

Arterial (about 30%) comes from the abdominal aorta via the hepatic artery. It is necessary for the normal functioning of the liver and to perform complex functions.

At the porta hepatis, the artery divides into two branches: the one going to the left supplies the left lobe, and the one going to the right supplies the right lobe.

From the right one, which is larger, a branch goes to the gall bladder. Sometimes a branch extends from the hepatic artery to the quadrate lobe.

Venous (about 70%) enters through the portal vein, which is collected from the small intestine, colon, rectum, stomach, pancreas, and spleen. This explains the biological role of the liver for humans: hazardous substances, poisons, medications, and processed products come from the intestines for neutralization and decontamination.

What is the blood supply algorithm?

Both sources of venous and arterial blood enter the organ through the gates of the liver, then they branch greatly, dividing into:

All these vessels have a thin muscle layer.

Penetrating into the lobule, the interlobular artery and vein merge into a single capillary network running along the hepatocytes to the central part of the lobule. In the center of the lobule, the capillaries gather into the central vein (it is devoid of a muscle layer). The central vein then flows into the interlobular, segmental, and lobar collecting vessels, forming 3–4 hepatic veins at the outlet at the hilum. They already have a good muscle layer, flow into the inferior vena cava, and it, in turn, enters the right atrium.

In general, the blood supply in the hepatic lobule can be displayed as follows:

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B→ K → Cv A→, where B and A are the interlobular artery and vein, K is the capillary, Cv is the central vein of the lobule.

Anastomoses

The portal vein has numerous connections (anastomoses) with other organs. This is necessary for extreme necessity: if there are disturbances in the liver, and due to high pressure resistance, blood cannot flow there, through anastomoses it goes into the venous bed of these organs and thus does not stagnate, but enters the heart, although it never purified.

The portal vein has anastomoses with:

Stomach.
The anterior wall of the abdomen and the veins located near the navel.
Esophagus.
Veins of the rectum.
Inferior vena cava.

Therefore, if a clear venous pattern in the form of a jellyfish appears on the abdomen, dilated veins are found during examination of the esophagus and rectum, we can safely say that the anastomoses are working in an enhanced mode, and in the portal vein the increased pressure prevents the passage of blood.

Blood pressure increases with cirrhosis and other diseases; this condition is called portal hypertension.

Regulation of blood supply

The liver normally contains about half a liter of blood. Its advancement is carried out due to the pressure difference: it comes from the arteries under a pressure of at least 110 mm. rt. st, which in the capillary network is reduced to 10 mm. rt. Art., in the portal veins it is within 5, and in the collecting venules it can even be 0.

Normal functioning of the organ requires constant maintenance of blood volume. To do this, the body has 3 types of regulation, which work thanks to the valve system of veins.

Myogenic regulation

Muscular regulation is most important because it is automatic. When muscles contract, they narrow the lumen of the vessel, and when they relax, they expand.

The structure of the walls of blood vessels

Thus, they regulate the constancy of blood supply under the influence of various factors: physical activity, during rest, pressure fluctuations, and diseases.

Humoral regulation

Carried out with the help of hormones:

Adrenalin. Produced during stress, it enters the blood and acts on the alpha-adrenergic receptors of the portal vein, causing its narrowing.

In small arterial vessels of the parenchyma, it acts on beta-adrenergic receptors and dilates intrahepatic vessels.

Norepinephrine and angiotensin. They affect both the venous and arterial systems equally, leading to a narrowing of all vessels, resulting in a decrease in the amount of blood supplied to the liver.

Acetylcholine. Dilates arterial vessels, which means improves blood supply to the liver. But it narrows the venules, i.e. prevents blood from flowing out of the organ. As a result, the blood is deposited in the liver.

Other hormones, such as thyroxine, glucocorticoids, insulin and glucagon, increase metabolic processes, which increases blood flow. Metabolites produced in tissues (histamine, prostaglandin, carbon dioxide) reduce portal inflow, but increase arterial blood flow.

Nervous regulation

It is slightly expressed, therefore it plays a minor role in the regulation of blood circulation.

Sympathetic innervation. Carried out by branches from the celiac plexus. Causes vasoconstriction, which reduces blood flow.
Parasympathetic. Comes from the vagus nerve (X pair). Has no effect.

An important indicator of impaired hepatic circulation is congested veins of the anastomoses.
Liver recovery occurs extremely slowly, and poor circulation only aggravates the situation.
The altered hormonal background of a person with diabetes mellitus, diseases of the thyroid gland and adrenal glands can make changes in the portal circulation.

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Liver circulation

The liver has a unique blood circulation, since most of its parenchymal cells are supplied with mixed venous (portal) and arterial blood. At rest, oxygen consumption by the liver is almost 20% of the oxygen consumption of the entire body; oxygen is supplied by the hepatic artery, which delivers 25-30% of the blood entering the liver and 40-50% of the oxygen consumed by the liver.

In the branch of the hepatic artery, blood is delivered at a pressure close to the pressure in the aorta (in the portal vein it does not exceed mmHg). When two blood streams connect

Rice. 18. Scheme of the structure of the hepatic lobule (according to C.G. Child): 1 - branch of the portal vein; 2 - branch of the hepatic artery; 3 - sinusoid; 4- central vein; 5 - liver tower (beam); 6 - interlobular bile duct; 7 - interlobular lymphatic vessel

in sinusoids their pressure is equalized (8-9 mm Hg). The section of the portal bed in which the most significant decrease in pressure occurs is localized near the sinusoids.

In critical conditions, hemodynamic disturbances of the liver are of significant importance: resistance to blood flow in the portal section of the hepatic bed increases, the flow of portal blood to the hepatocyte decreases, and the liver switches to a predominantly arterial blood supply. The blood flow through the sinusoids slows down, and conglomeration of blood cells occurs in the capillaries and sinusoids. Due to the development of capillary spasm and shutdown of a significant part

Fig. 19. Scheme of the structure of the intrahepatic bile ducts (according to N. Rorre, F. Schaffner): 1 - branch of the portal vein; 2 - sinusoids; 3 - stellate reticuloendotheliocyte; 4 - hepatocyte; 5 - intercellular bile canaliculus; 6 - interlobular bile duct; 7 - interlobular bile duct; 8 - lymphatic vessel

sinusoids, blood circulation in the liver begins to occur through a system of shunts, oxygen tension in the liver tissue decreases, which leads to hypoxia of the organ. According to E.I. Galperin (1988), changes in microcirculation with blockade of portal blood flow are an autonomous reaction of the liver that occurs in response to an adverse effect. In the light of modern concepts, it is believed that it is disorders of the hepatic microcirculation and disorders of transcapillary metabolism that play a leading role in the pathogenesis of acute liver failure.

Features of portal circulation and blood supply to the liver

V.V. Bratus, T.V. Talaeva “Circulatory system: principles of organization and regulation of functional activity”

Venous (stagnant, passive) hyperemia is a pathological change in blood circulation caused by difficulty in the outflow of venous blood while maintaining its delivery to the tissues through the corresponding arteries. Venous congestion can be general and local, acute and chronic.

The myocardium of the atria and ventricles, separated by fibrous rings, is synchronized in its work by the conduction system of the heart, which is common to all its departments (Fig. 1.30).

The main source of blood supply to the heart is the coronary arteries (Fig. 1.22). The left and right coronary arteries branch from the initial part of the ascending aorta in the left and right sinuses. The location of each coronary artery varies both in height and circumference of the aorta. The mouth of the left vein.

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Blood circulation of the liver.

We admire the amazing creations of man. And we take for granted the vital activity of the body, the harmonious relationship between its structure and functions. Almost none of us are surprised, for example, by the constant, uninterrupted and accurate functioning of the liver that does not stop even for a minute throughout our lives. Ancient doctors worshiped the functions of organs that were mysterious to them and treated them as a “miracle.” Hippocrates considered the liver to be the “engine of nutrition”, Galen - the central hematopoietic and circulatory organ.

Even the reformer of medieval medicine Vesalius, the founder of scientific anatomy, wrote that “. the liver is perhaps the most important of the digestive organs and the workshop of thick blood, which is the fuel of the soul, requiring food and drink and that which is necessary to the nature of the body.”

Harvey and Malpighi said a new and, finally, scientific word about blood circulation in the body. And the research of biologists and physicians of the 19th-20th centuries brought a lot of new valuable data. And although even today it cannot be said that the functions of the liver are fully understood, we can rightfully say: not many vital processes in the body occur without the active participation of the liver. So, we will talk about the structure and functions, and most importantly, about the amazing and very unique blood circulation of the liver.

The structure of the liver.

The main functional unit of the liver is the hepatic lobule. There are about a million of them, and each lobule is built from approximately 350 thousand liver cells, arranged in radii, like spokes in a wheel. In the center of the lobule, like the axis of a wheel, runs a blood vessel - the central vein - this is the structure of the hepatic lobule in brief.

Liver cells, unlike cells of other organs, are short prisms with eight surfaces. The smallest blood vessels of the liver pass through tubes located at the corners of the cells. The tubes running in the middle of the liver cells are bile capillaries, through which the bile produced in the cells flows.

So, blood and bile. They flow in the liver towards each other; the first - from the periphery of the hepatic lobules to their center; the second - on the contrary - from the center of the hepatic lobules to the periphery. The opposite directions in the flow of bile and blood are explained by the complex functions of the liver - the largest digestive gland that produces bile, and the organ that receives and processes blood. What are the functions of the liver?

First of all, the liver is an active participant in carbohydrate metabolism. There is no human organ richer in glycogen, the so-called animal sugar, than the liver. It is a glycogen “depot”. The main source of glycogen is carbohydrates, absorbed into the blood from the intestines and transported through the portal vein system to the liver.

The liver is a blood filter.

The role of the liver in metabolism is no less important. Foreign substances formed during the transformation of proteins are poisons for the body. Passing through the circulatory system of the liver, they linger in its cells for some time and are neutralized. Thus, the liver, a faithful guardian of the body, saves it from severe poisoning.

The liver neutralizes not only foreign proteins, but also many potent poisons. For example, a poison such as morphine, passing through the liver cells, does not exhibit a toxic effect even in such quantities that would be fatal to the body if it were introduced into the blood that had already left the liver. The same can be said about pathogens. If the blood saturated with them undergoes the “quarantine service” of the liver cells, much fewer dangerous enemies spread in the body.

The participation of the liver in protein metabolism is not limited to the retention of foreign proteins. As blood flows through the liver, amino acids are partially accumulated here and from them “reserve protein” is synthesized, which is easily used by the body when little protein comes from food. Thus, after blood loss, the normal content of some blood plasma proteins is quickly restored. If the functions of the liver are impaired, say, as a result of severe poisoning, then the restoration of the normal protein composition of the blood is extremely slow.

Finally, during intrauterine development, the child’s liver has a hematopoietic function, producing red blood cells - erythrocytes.

So, the hematopoietic function, participation in carbohydrate and protein metabolism, the most important role in protecting the body from harmful substances - all these and other various functions of the liver are carried out by liver cells. And their need for nutrients and oxygen is provided by the complex, very unique blood circulation of the organ - the portal vein system and the hepatic artery.

The liver is located in the upper abdominal cavity under the diaphragm. On its lower surface three clear grooves are visible: two longitudinal ones are connected by one transverse one in the shape of the letter “n”. The transverse groove is the so-called portal of the liver, where the hepatic artery and nerves enter, from where the lymphatic vessels and the excretory duct exit, directing bile to the duodenum. The portal vein also enters the portal of the liver.

The veins extending from the digestive organs gradually enlarge and form the superior and inferior mesenteric veins. They, in turn, merge with the splenic vein and pass into a large portal vein 3-4 centimeters long. The portal vein collects blood not only from the digestive organs. One of its roots is the splenic vein, which contains a certain amount of newly formed white blood cells - leukocytes produced in the spleen.

The blood passing through the spleen, thanks to the protective activity of this organ, is freed from “waste” red cells and pathogenic microbes, foreign particles, etc. that have entered the bloodstream. Thus, the spleen helps the liver, to some extent cleansing and neutralizing its portions of the blood.

Having entered the gate of the liver, the portal vein divides into two or three branches located between the lobes of the liver. These branches, as a result of repeated and sequential division, give rise to a large number of interlobular veins. The interlobular veins, located along the periphery of the hepatic lobule, and the central vein, lying in its center, are connected by capillaries, forming the so-called miraculous venous network. It differs from all other capillary networks, intended mainly for nutrition and tissue respiration, in that both before and after branching into capillaries, the composition of the blood in the network remains venous. In ordinary capillary networks, as is known, arterial blood passes into venous blood.

This feature is determined by the exclusive role of the liver itself. Blood rich in nutrients is eagerly awaited by every cell and every tissue in the body. The blood receives nutrients in the walls of the gastrointestinal tract. And before it gets to the heart, which sends the blood on a further journey through the blood vessels, it will certainly go through a cleansing stage in the liver.

Liver cells are directly adjacent to the very thin wall of the blood capillary. Thanks to this, they quickly absorb nutrients from the blood and retain harmful metabolic products, process them, and just as quickly, as needed, can release into the blood what was previously accumulated in them. All these processes are regulated and controlled by the nervous system.

To carry out complex functions and normal life, the liver naturally needs arterial blood rich in oxygen. Oxygen is brought to the liver by the hepatic artery. It gives rise to interlobular arteries, which then break up into a network of blood capillaries through which arterial blood flows. But these arterial capillaries immediately flow into the capillary network of the hepatic lobule, and in it, as we have already said, venous blood flows.

Here, in the capillary network of the liver lobule, mixing of arterial and venous blood occurs. This is another feature of the blood circulation of the liver: the liver tissue receives oxygen not only from the arterial capillaries, but also from the capillaries through which mixed venous and arterial blood flows. This additional enrichment of liver cells with oxygen is very important for the body.

So, thanks to the existence of the portal circulation, our blood flows through the following two capillary networks in succession: the gastrointestinal tract and the spleen, and then the liver. In the liver, all substances that enter the blood through the portal system are processed and accumulated, and then, as needed, they are again released into the blood or, together with bile, return to the intestines.

Some liver diseases disrupt its “quarantine” functions and impede blood flow. In such cases, the so-called anastomoses become of great importance - vessels connecting the portal vein or its roots with adjacent veins that flow directly into the inferior and superior vena cava, and, consequently, into the heart.

In a healthy person, anastomoses either do not participate in the blood circulation at all, or participate very little. When the liver becomes a “stumbling block” in the path of blood flow, the anastomoses begin to work.

For example, such a connection between the branches of the portal and vena cava is located on the anterior abdominal wall in the navel area. When blood flow through the portal vein is obstructed, blood rushes into the superior and inferior vena cava, bypassing the portal vein. At the same time, the anastomoses significantly expand and twist, taking on a bizarre shape. Ancient doctors called this system of anastomoses the “head of Medusa,” by analogy with the head of one of the three winged sisters (female monsters) described in Greek mythology - Medusa - Gorgons with snakes instead of hair on their heads.

Participation in the blood circulation of anastomoses is a kind of “vacation” for the liver, during which it gets the opportunity to restore its functions that are extremely necessary for the body.

The structure and functions of the liver and its circulatory system, which are irreplaceable in the body, are surprisingly expedient. But their possibilities are not unlimited. And a person should not for a moment, has no right to forget that the liver - his faithful friend and protector - also needs protection from the abuse of carbohydrates, fats, proteins, alcohol and nicotine. Take care of your liver!

Features of blood supply to the liver

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The enrichment of liver tissue occurs through two vessels: the artery and portal vein, which are branched in the left and right lobes of the organ. Both vessels enter the gland through the “gate” located at the bottom of the right lobe. The blood supply to the liver is distributed in the following percentage: 75% of the blood passes through the portal vein, and 25% through the artery. The anatomy of the liver involves the passage of 1.5 liters of valuable fluid every 60 seconds. at pressure in the portal vessel - domm Hg. Art., in the artery - up to 120 mm Hg. Art.

Features of the liver circulatory system

The liver plays a major role in metabolic processes occurring in the body. The quality of an organ’s functions depends on its blood supply. The liver tissues are enriched with blood from the artery, which is saturated with oxygen and nutrients. Valuable fluid enters the parenchyma from the celiac trunk. Venous blood, saturated with carbon dioxide and coming from the spleen and intestines, leaves the liver through the portal vessel.

The anatomy of the liver includes two structural units called lobules, which are similar to a faceted prism (the edges are created by rows of hepatocytes). Each lobule has a developed vascular network, consisting of an interlobular vein, artery, bile duct, and lymphatic vessels. The structure of each lobule suggests the presence of 3 blood streams:

for the flow of blood serum to the lobules;
for microcirculation inside the structural unit;
to drain blood from the liver.

25-30% of the blood volume circulates through the arterial network under pressure up to 120 mmHg. Art., in the portal vessel - 70-75% (10-12 mm Hg). In sinusoids, the pressure does not exceed 3-5 mm Hg. Art., in the veins - 2-3 mm Hg. Art. If pressure increases, excess blood is released into the anastomoses between the vessels. After processing, arterial blood is directed into the capillary network, and then sequentially enters the hepatic vein system and accumulates in the lower hollow vessel.

The blood circulation rate in the liver is 100 ml/min, but with pathological dilatation of blood vessels due to their atony, this value can increase to 5000 ml/min. (about 3 times).

The interdependence of arteries and veins in the liver determines the stability of blood flow. When blood flow in the portal vein increases (for example, against the background of functional hyperemia of the gastrointestinal tract during digestion), the rate of movement of red liquid through the artery decreases. And, conversely, when the blood circulation rate in the vein decreases, perfusion in the artery increases.

The histology of the liver circulatory system suggests the presence of the following structural units:

main vessels: hepatic artery (with oxygenated blood) and portal vein (with blood from unpaired peritoneal organs);
an extensive network of vessels that flow into each other through lobar, segmental, interlobular, perilobular, capillary structures with a connection at the end into an intralobular sinusoidal capillary;
efferent vessel - collecting vein, which contains mixed blood from the sinusoidal capillary and directs it to the sublobular vein;
vena cava, designed to collect purified venous blood.

If for some reason blood cannot move at normal speed through the portal vein or artery, it is redirected to the anastomoses. A special feature of the structure of these structural elements is the ability to communicate with the blood supply system of the liver with other organs. True, in this case, the regulation of blood flow and redistribution of the red liquid is carried out without purifying it, so it, without lingering in the liver, immediately enters the heart.

The portal vein has anastomoses with the following organs:

stomach;
the anterior wall of the peritoneum through the periumbilical veins;
esophagus;
rectal section;
the lower part of the liver itself through the vena cava.

Consequently, if a distinct venous pattern appears on the abdomen, resembling the head of a jellyfish, varicose veins of the esophagus and rectum are detected, it should be stated that the anastomoses are working in an enhanced mode, and in the portal vein there is a strong excess of pressure that prevents the passage of blood.

Regulation of blood supply to the liver

The normal amount of blood in the liver is considered to be 1.5 liters. Blood circulation is carried out due to the difference in pressure in the arterial and venous group of vessels. To ensure stable blood supply to the organ and its proper functioning, there is a special system for regulating blood flow. To do this, there are 3 types of regulation of blood supply, working through a special valve system of veins.

Myogenic

This regulatory system is responsible for muscular contraction of the vascular walls. Due to muscle tone, the lumen of blood vessels, when they contract, narrows, and when they relax, they expand. With the help of this process, the pressure and speed of blood flow increases or decreases, that is, the stability of the blood supply is regulated under the influence of:

Excessive physical activity and pressure fluctuations negatively affect the tone of liver tissue.

exogenous factors such as physical activity, rest;
endogenous factors, for example, during pressure fluctuations, the development of various diseases.

Features of myogenic regulation:

ensuring a high degree of autoregulation of hepatic blood flow;
maintaining constant pressure in the sinusoids.

Humoral

Regulation of this type occurs through hormones, such as:

Hormonal imbalances can negatively impact liver function and integrity.

Adrenalin. It is produced during stress and affects the α-adrenergic receptors of the portal vessel, causing relaxation of the smooth muscles of the intrahepatic vascular walls and a decrease in pressure in the blood flow system.
Norepinephrine and angiotensin. They have the same effect on the venous and arterial systems, causing a narrowing of the lumen of their vessels, which leads to a decrease in the amount of blood entering the organ. The process is started by increasing vascular resistance in both channels (venous and arterial).
Acetylcholine. The hormone helps to expand the lumen of arterial vessels, which means it improves blood supply to the organ. But at the same time, a narrowing of the venules occurs, therefore, the outflow of blood from the liver is disrupted, which provokes the deposition of blood into the hepatic parenchyma and a jump in portal pressure.
Metabolic products and tissue hormones. Substances dilate arterioles and narrow portal venules. There is a decrease in venous circulation against the background of an increase in the flow rate of arterial blood with an increase in its total volume.
Other hormones - thyroxine, glucocorticoids, insulin, glucagon. The substances cause an increase in metabolic processes, while blood flow increases against the background of a decrease in portal inflow and an increase in arterial blood supply. There is a theory that adrenaline and tissue metabolites influence these hormones.

Nervous

The influence of this form of regulation is secondary. There are two types of regulation:

Sympathetic innervation, in which the process is controlled by the branches of the celiac plexus. The system leads to a narrowing of the lumen of blood vessels and a decrease in the amount of incoming blood.
Parasympathetic innervation, in which nerve impulses come from the vagus nerve. But these signals have no effect on the blood supply to the organ.

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The portal vein (PV, portal vein) is one of the largest vascular trunks in the human body. Without it, normal functioning of the digestive system and adequate blood detoxification are impossible. The pathology of this vessel does not go unnoticed, causing serious consequences.

The hepatic portal vein system collects blood coming from the abdominal organs. The vessel is formed by connecting the superior and inferior mesenteric and splenic veins. In some people, the inferior mesenteric vein drains into the splenic vein, and then the junction of the superior mesenteric and splenic veins forms the trunk of the PV.

Anatomical features of blood circulation in the portal vein system

The anatomy of the portal vein system (portal system) is complex. This is a kind of additional circle of venous circulation, necessary to cleanse the plasma of toxins and unnecessary metabolites, without which they would immediately fall into the inferior hollow, then into the heart and further into the pulmonary circle and the arterial part of the large one.

The latter phenomenon is observed when the liver parenchyma is damaged, for example, in patients with cirrhosis. It is the absence of an additional “filter” on the way of venous blood from the digestive system that creates the preconditions for severe intoxication with metabolic products.

Having studied the basics of anatomy at school, many remember that most organs of our body include an artery that carries blood rich in oxygen and nutritional components, and a vein emerges that carries “waste” blood to the right half of the heart and lungs.

The portal vein system is structured somewhat differently; its peculiarity can be considered the fact that in addition to the artery, the liver enters a venous vessel, the blood from which again enters the hepatic veins, passing through the parenchyma of the organ. It is as if additional blood flow is created, the work of which determines the condition of the entire organism.

The formation of the portal system occurs due to large venous trunks merging with each other near the liver. The mesenteric veins transport blood from the intestinal loops, the splenic vein leaves the spleen and receives blood from the veins of the stomach and pancreas. Behind the head of the pancreas, the venous “highways” connect, giving rise to the portal system.

Between the layers of the pancreaticoduodenal ligament, the gastric, periumbilical and prepyloric veins flow into the PV. In this area, the PV is located behind the hepatic artery and the common bile duct, together with which it follows to the porta hepatis.

At the gates of the liver, or not reaching them one to one and a half centimeters, division occurs into the right and left branches of the portal vein, which enter both hepatic lobes and there break up into smaller venous vessels. Reaching the hepatic lobule, venules entwine it from the outside, enter inside, and after the blood is neutralized upon contact with hepatocytes, it enters the central veins emerging from the center of each lobule. The central veins gather into larger ones and form hepatic veins, which carry blood from the liver and flow into.

A change in the size of the vein is of great diagnostic importance and can indicate various pathologies - cirrhosis, venous thrombosis, pathology of the spleen and pancreas, etc. The length of the portal vein of the liver is normally approximately 6-8 cm, and the diameter of the lumen is up to one and a half centimeters.

The portal vein system does not exist in isolation from other vascular systems. Nature provides the possibility of dumping “excess” blood into other veins if a hemodynamic disturbance occurs in this section. It is clear that the possibilities of such a discharge are limited and cannot last indefinitely, but they make it possible to at least partially compensate for the patient’s condition in case of severe diseases of the liver parenchyma or thrombosis of the vein itself, although sometimes they themselves become the cause of dangerous conditions (bleeding).

The connection between the portal vein and other venous collectors of the body is carried out thanks to anastomoses, the localization of which is well known to surgeons, who quite often encounter acute bleeding from anastomotic areas.

Anastomoses of the portal and vena cava are not pronounced in a healthy body, since they do not bear any load. In pathology, when the flow of blood into the liver becomes difficult, the portal vein expands, the pressure in it increases, and the blood is forced to look for other outflow routes, which become anastomoses.

These anastomoses are called portocaval, that is, the blood that should have gone to the IV goes into the vena cava through other vessels that unite both blood flow basins.

The most significant anastomoses of the portal vein include:

Connection of gastric and esophageal veins;
Anastomoses between the veins of the rectum;
The junction of the veins of the anterior wall of the abdomen;
Anastomoses between the veins of the digestive organs with the veins of the retroperitoneal space.

In the clinic, the anastomosis between the gastric and esophageal vessels is of greatest importance. If the movement of blood through the veins is disrupted, it is dilated, portal hypertension increases, then the blood rushes into the flowing vessels - the gastric veins. The latter have a system of collaterals with the esophageal, where venous blood that does not go to the liver is redirected.

Since the ability to discharge blood into the vena cava through the esophageal veins is limited, overloading them with excess volume leads to varicose veins with the likelihood of bleeding, often fatal. The longitudinally located veins of the lower and middle thirds of the esophagus do not have the ability to collapse, but are at risk of injury when eating, gag reflex, and reflux from the stomach. Bleeding from varicose veins of the esophagus and the initial part of the stomach is not uncommon in liver cirrhosis.

From the rectum, venous outflow occurs both into the venous system (upper third) and directly into the lower cavity, bypassing the liver. With an increase in pressure in the portal system, stagnation inevitably develops in the veins of the upper part of the organ, from where it is discharged through collaterals into the middle vein of the rectum. Clinically, this is expressed in varicose hemorrhoids - hemorrhoids develop.

The third junction of the two venous pools is the abdominal wall, where the veins of the peri-umbilical region take on “excess” blood and expand towards the periphery. Figuratively, this phenomenon is called the “head of Medusa” because of some external resemblance to the head of the mythical Gorgon Medusa, who had writhing snakes on her head instead of hair.

The anastomoses between the veins of the retroperitoneal space and the PV are not as pronounced as those described above, it is impossible to trace them by external signs, and they are not prone to bleeding.

Video: lecture on veins of the systemic circulation

Video: basic information about the portal vein from the notes

Pathology of the portal system

Among the pathological conditions in which the IV system is involved are:

Thrombosis (extra- and intrahepatic);
Portal hypertension syndrome (PHS) associated with liver pathology;
Cavernous transformation;
Purulent inflammatory process.

Portal vein thrombosis

Portal vein thrombosis (PVT) is a dangerous condition in which blood clots appear in the PV, preventing its movement towards the liver. This pathology is accompanied by an increase in pressure in the vessels - portal hypertension.

4 stages of portal vein thrombosis

According to statistics, among residents of developing regions, LPG is accompanied by thrombus formation in the veins in a third of cases. In more than half of patients who die from cirrhosis, thrombotic clots can be detected postmortem.

The causes of thrombosis are considered:

Cirrhosis of the liver;
Malignant intestinal tumors;
Inflammation of the umbilical vein during catheterization in infants;
Inflammatory processes in the digestive organs - cholecystitis, pancreatitis, intestinal ulcers, colitis, etc.;
Injuries; surgical interventions (bypass surgery, removal of the spleen, gallbladder, liver transplant);
Blood clotting disorders, including certain neoplasias (polycythemia, pancreatic cancer);
Some infections (tuberculosis of portal lymph nodes, cytomegalovirus inflammation).

Among the very rare causes of PVT include pregnancy and long-term use of oral contraceptives, especially if the woman has crossed the age of 35-40.

Symptoms of PVT consists of severe abdominal pain, nausea, dyspeptic disorders, vomiting. Possible increase in body temperature, bleeding from hemorrhoids.

Chronic progressive thrombosis, when blood circulation through the vessel is partially preserved, will be accompanied by an increase in the typical picture of LPG - fluid will accumulate in the abdomen, the spleen will enlarge, giving characteristic heaviness or pain in the left hypochondrium, and the veins of the esophagus will dilate with a high risk of dangerous bleeding.

The main way to diagnose PVT is ultrasound, and a thrombus in the portal vein looks like a dense (hyperechoic) formation that fills both the lumen of the vein itself and its branches. If ultrasound is supplemented with Doppler ultrasound, then there will be no blood flow in the affected area. Cavernous degeneration of blood vessels due to dilation of small-caliber veins is also considered characteristic.

Small thrombi of the portal system can be detected by endoscopic ultrasound, and CT and MRI make it possible to determine the exact causes and look for possible complications of thrombus formation.

Video: incomplete portal vein thrombosis on ultrasound

Portal hypertension syndrome

Currently answering questions: A. Olesya Valerievna, Ph.D., teacher at a medical university

The enrichment of liver tissue occurs through two vessels: the artery and portal vein, which are branched in the left and right lobes of the organ. Both vessels enter the gland through the “gate” located at the bottom of the right lobe. The blood supply to the liver is distributed in the following percentage: 75% of the blood passes through the portal vein, and 25% through the artery. involves the passage of 1.5 liters of valuable fluid every 60 seconds. when the pressure in the portal vessel is up to 10-12 mm Hg. Art., in the artery - up to 120 mm Hg. Art.

The liver suffers greatly from a lack of blood supply, and with this, the entire human body.

Features of the liver circulatory system

for the flow of blood serum to the lobules;
for microcirculation inside the structural unit;
to drain blood from the liver.

25-30% of the blood volume circulates through the arterial network under pressure up to 120 mmHg. Art., in the portal vessel - 70-75% (10-12 mm Hg. Art.). In sinusoids, the pressure does not exceed 3-5 mm Hg. Art., in the veins - 2-3 mm Hg. Art. If pressure increases, excess blood is released into the anastomoses between the vessels. After processing, arterial blood is directed into the capillary network, and then sequentially enters the hepatic vein system and accumulates in the lower hollow vessel.

The blood circulation rate in the liver is 100 ml/min, but with pathological dilatation of blood vessels due to their atony, this value can increase to 5000 ml/min. (about 3 times).

The histology of the liver circulatory system suggests the presence of the following structural units:

main vessels: hepatic artery (with oxygenated blood) and portal vein (with blood from unpaired peritoneal organs);
an extensive network of vessels that flow into each other through lobar, segmental, interlobular, perilobular, capillary structures with a connection at the end into an intralobular sinusoidal capillary;
efferent vessel - collecting vein, which contains mixed blood from the sinusoidal capillary and directs it to the sublobular vein;
vena cava, designed to collect purified venous blood.

The portal vein has anastomoses with the following organs:

stomach;
the anterior wall of the peritoneum through the periumbilical veins;
esophagus;
rectal section;
the lower part of the liver itself through the vena cava.

Regulation of blood supply to the liver

Myogenic

Excessive physical activity and pressure fluctuations negatively affect the tone of liver tissue.

exogenous factors such as physical activity, rest;
endogenous factors, for example, during pressure fluctuations, the development of various diseases.

Features of myogenic regulation:

ensuring a high degree of autoregulation of hepatic blood flow;
maintaining constant pressure in the sinusoids.

Humoral

Regulation of this type occurs through hormones, such as:

Hormonal imbalances can negatively impact liver function and integrity.

Adrenalin. It is produced during stress and affects the α-adrenergic receptors of the portal vessel, causing relaxation of the smooth muscles of the intrahepatic vascular walls and a decrease in pressure in the blood flow system.
Norepinephrine and angiotensin. They have the same effect on the venous and arterial systems, causing a narrowing of the lumen of their vessels, which leads to a decrease in the amount of blood entering the organ. The process is started by increasing vascular resistance in both channels (venous and arterial).
Acetylcholine. The hormone helps to expand the lumen of arterial vessels, which means it improves blood supply to the organ. But at the same time, a narrowing of the venules occurs, therefore, the outflow of blood from the liver is disrupted, which provokes the deposition of blood into the hepatic parenchyma and a jump in portal pressure.
Metabolic products and tissue hormones. Substances dilate arterioles and narrow portal venules. There is a decrease in venous circulation against the background of an increase in the flow rate of arterial blood with an increase in its total volume.
Other hormones - thyroxine, glucocorticoids, insulin, glucagon. The substances cause an increase in metabolic processes, while blood flow increases against the background of a decrease in portal inflow and an increase in arterial blood supply. There is a theory that adrenaline and tissue metabolites influence these hormones.

Rice. 1. Topography of the liver; 1 - hepar; 2 - lig. falciforme hepatis; 3 - ventriculus; 4 - lien; 5 - colon transversum; 6 - lig. hepatogastricum.

The weight of a human liver reaches 1.5 kg, its consistency is soft, its color is reddish-brown, and its shape resembles a large shell. The convex diaphragmatic surface of the liver (facies diaphragmatica) faces upward and posteriorly. Anteriorly and especially to the left, the liver becomes thinner (Fig. 1 and 2). The lower visceral surface (facies visceralis) is concave. The liver occupies the right hypochondrium and extends through the epigastric region into the left hypochondrium. The anterior pointed edge of the liver usually does not extend from under the right costal arch to the outer edge of the right rectus abdominis muscle. Next, the lower border of the liver passes obliquely to the junction of the cartilages of the VII and VIII left ribs. The liver occupies almost the entire dome of the diaphragm. On the left it comes into contact with the stomach, below - with the right kidney, with the transverse colon and duodenum.

Rice. 2. Liver (top): 1 - lis. triangulare deist.; 2 - diaphragm; 3 - lig. coronarium hepatis; 4 - lig. triangulare sin.; 5 - appendix fibrosa hepatis; 6 - lobus sin. hepatis; 7 - lig. falciforme hepatis; 8 - lig. teres hepatis; 9 - incisura lig. teretis; 10 - margo inf.; 11 - vesica fellea (fundus); 12 - lobus dext. hepatis.
Rice. 3. Liver (back): 1 - lig. triangulare sin.; 2 - impressio gastrica; 3 - lig. coronarium hepatis; 4 - impressio oesophagea; 5 - lig. venosum hepatis; 6 - lobus caudatus hepatis; 7 - lig. falciforme hepatis; 8 - v. hepatica; 9 - lobus dext. hepatis; 10 - v. cava inf.; 11 - lig. v. cavae; 12 - facies diaphragmatica; 13 - impressio suprarenalis; 14 - processus caudatus; 13 - collum vesicae felleae; 16 - lig. triangulare dext.; 17 - impressio renalis; 18 - impressio colica; 19 - impressio duodenalis; 20 - vesica fellea; 21 - ductus choledochus; 22 - v. portae; 23 - lobus quadratus; 24 - lig. falciforme hepatis; 26 - a. hepatica propria; 26 - lig. teres hepatis; 27 - porta hepatis; 28 - tuber omentale; 29 - lobus sin.; 30 - appendix fibrosa hepatis.

The liver, with the exception of the upper-posterior surface attached to the diaphragm, is covered with peritoneum. The transition of the peritoneum from the diaphragm to the liver along the frontal plane is designated as the coronary ligament (lig. coronarium hepatis), the transition along the sagittal plane is designated as the falciform ligament (lig. falciforme hepatis), dividing the diaphragmatic surface of the liver into the right and left lobes (lobus hepatis dexter et sinister ). The visceral surface is divided into right, left, caudate (lobus caudatus) and square (lobus quadratus) lobes by two longitudinal grooves and one transverse one (porta of the liver). The gallbladder (see) is placed in the recess of the right longitudinal groove in front, and the inferior vena cava in the back. The left longitudinal groove includes the round ligament of the liver (lig. teres hepatis), formed from the neglected umbilical vein. Here it passes into the venous ligament (lig. venosum) - the remnant of the overgrown ductus venosus. Under the peritoneum on top of the liver there is a connective tissue capsule.

The portal vein (see) and the hepatic artery entering the gate of the liver and the lymphatic vessels and bile duct exiting the gate (Fig. 3) are covered with layers of peritoneum that make up the hepatoduodenal ligament (lig. hepatoduodenal). Its continuation is the hepatogastric ligament (lig. hepatogastricum) - the lesser omentum. A sheet of peritoneum stretches down to the right kidney from the liver - the hepatorenal ligament (lig. hepatorenale). Between the liver and the diaphragm on the sides of the falciform ligament, the right and left hepatic bursae (bursa hepatica dext. et sin.) are distinguished; between the liver and the stomach behind the lesser omentum is the omental bursa (bursa omentalis). Liver segments are shown in Fig.

The main segments of the liver: I - anterior segment: II - posterior segment; III - medial segment; IV - lateral segment. 1 - ductus cholcdoclius; 2 - v. portae; 3 - a. hepatica.

Rice. 4. Scheme of the structure of the lymphatic vessels of the liver: 1 - retrosternal lymph nodes; 2 - anterior group of diaphragmatic nodes; 3 - posterior group of diaphragmatic nodes; 4 - inferior vena cava; 5 - inferior phrenic artery; b - thoracic aorta; 7 - celiac lymph nodes; 8 - hepatic veins; 9 - hepatic lymph nodes; 10 - deep lymphatic vessels; 11 - superficial lymphatic vessels; 12 - diaphragm.

The bloodstream of the liver consists of the intraorgan part of the venous portal system, the drainage system of the hepatic veins and the system of hepatic arteries. Arterial blood supply to the liver is carried out by the hepatic artery (from the celiac artery system), which, entering the portal of the liver, is divided into right and left branches. Often there are accessory hepatic arteries coming from the branches of the celiac artery and from the superior mesenteric artery. The portal vein brings the bulk of blood to the liver. It is divided into lobar veins, from which segmental veins originate. Continuing to divide, the branches of the portal vein first become interlobular, and then thin septal venules, turning into capillaries - sinusoids of the lobule. The septal arterioles also open here, completing the branching of the segmental intrahepatic arteries. Thus, mixed blood flows through the sinusoids. Sinusoids are equipped with devices to regulate blood flow. As a result of the fusion of sinusoids, the central veins of the lobules are formed, from which blood flows first into the sublobular, and then into the collecting veins and, finally, into 3-4 hepatic veins. The latter open into the inferior vena cava. The lymphatic system of the liver (Fig. 4) begins with perilobular and superficial networks of capillaries, folding into superficial and deep lymphatic vessels, through which lymph flows either to the lymph nodes at the porta hepatis, or to the subphrenic nodes around the inferior vena cava. The vagus nerves and branches of the solar plexus take part in the innervation of the liver, thanks to which autonomic and afferent innervation is provided.

See also Portal circulation.

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The hepatic mass fills the right dome of the diaphragm and extends to the left of the body midline below the heart (Fig. 1 A). The most typical shape of the anterior surface of the liver, namely its decreasing volume to the left of the falciform ligament, is very convenient for laparoscopic access to extrahepatic biliary structures. The apex of the lateral segment of the left lobe of the liver may have the form of a fibrous continuation, which is an embryonic remnant (Fig. 1 B). Less common is enlargement of the right lobe of the liver downwards, which may cause additional difficulties (Fig. 1 B). The edge of the liver is directed from above to the left and below to the right, leaving part of the anterior wall of the stomach and pylorus open on the left and the proximal part of the transverse colon on the right. The tip of an unchanged gallbladder may protrude between the colon and the lower edge of the liver.

When studying the anatomy of the liver in three projections, one must always correlate it with the anatomy of neighboring organs. The relationship between the liver and the diaphragm is determined by the commonality of their embryonic origin - the transverse septum (Fig. 2 A). The areas of the liver not covered by peritoneum are the result of the transition of the parietal peritoneum from the lower surface of the diaphragm to the liver. This feature of the distribution of the peritoneum forms a diamond-shaped crown above the liver, called the coronary ligament.

The border of attachment of the “ligaments” is located on the upper surface of the liver far above and posteriorly, forming a deep suprahepatic pocket on the right. In the center of this area is the confluence of the inferior vena cava with the main hepatic veins. Anteriorly, the coronary ligament passes into the falciform ligament, the head portion of the ventral mesentery. Along the edges, left and right, the anterior and posterior surfaces of the coronary ligament come together at an acute angle and form triangular ligaments.

When the surgeon transects the left triangular ligament to mobilize the lateral segment of the left lobe of the liver, he must be aware of the proximity of the hepatic veins and the inferior vena cava. Access to these vessels, if damaged, will be extremely difficult due to their deep localization. Small veins running from the posterior surface of the liver directly to the inferior vena cava reflect the peculiarity of the evolutionary development of the vena cava from the dorsal part of the venous plexus of the liver. Note the location of the inferior left phrenic vein, which passes along the anterior semicircle of the esophageal opening of the diaphragm. This is a very common anatomy variant.

The organs of the upper floor of the abdominal cavity, when viewed on a CT scan slice, are located in the shape of a kidney or bean (Figure 2 B). The spine and large vessels fill the cavity, and the organs themselves are located posteriorly and to the sides, in the diaphragmatic recesses. The most posterior position is occupied by the kidneys.

In a sagittal section (Fig. 3), the abdominal cavity has a wedge shape due to the slope of the lumbar spine and adjacent lumbar muscles. The hepatorenal volvulus (Morrison's pouch) is the outermost space of the abdominal cavity. To the right and behind, the lower surface of the liver goes around the kidney with perinephric fiber, and in front of it is the hepatic angle of the colon.

A sagittal section of the right upper quadrant of the abdominal cavity (Fig. 4) shows that the inferior vena cava is located in the center of the abdominal cavity, and immediately in front of it is the hepatoduodenal ligament with the portal vein. On a frontal cholangiogram, the common bile duct usually runs along the right edge of the lumbar vertebrae. To view small details without overlapping images of underlying structures, the patient should be turned slightly to the right (Fig. 5).

If the liver is elevated, the hepatogastric omentum becomes visible, another derivative of the ventral mesentery, which extends from the lesser curvature of the stomach to the groove of the venous ligament and the porta hepatis (Fig. 6). The free edge of the omentum surrounds the bile ducts and forms the hepatoduodenal ligament. The place of contact between the anterior surface of the fundus of the stomach and the lower surface of the lateral segment of the left lobe of the liver is also visible. The initial section of the duodenum, previously closed by the edge of the liver, is visible, and the relative position of the intestine and the lower surface of the quadrate lobe, as well as the gallbladder, is visible. And finally, on the right, the relative position of the hepatic angle of the colon, the right lobe of the liver and the gallbladder is open.

When the stomach and duodenum are retracted, the root of the mesentery of the transverse colon and the boundaries of the omental bursa behind the lesser omentum become visible (Fig. 7). In the upper part of the bursa, the caudate lobe of the liver is visible, which is usually of considerable size. The fold of peritoneum between the liver and pancreas has the appearance of a ridge formed by the hepatic artery, passing through the retroperitoneal space of the omental bursa and turning into the hepatoduodenal ligament.

When the posterior layer of the parietal peritoneum is separated, the anatomical structures of the porta hepatis and their relationship with the pancreas are exposed (Fig. 8). The trunk of the celiac artery is usually divided into three branches, giving rise to the left gastric artery, hepatic and splenic arteries.

And let’s complete the review of the organs of the upper abdominal cavity with a rear view (Fig. 9). The right lobe of the liver extends posteriorly over the superior pole of the right kidney, so that the right adrenal gland is enclosed between the kidney, liver, and inferior vena cava. The inferior vena cava, for a greater or lesser extent, is located in the fossa separating the right and left lobes of the liver. To the left of the vena cava lies the caudate lobe of the liver.

The gastrohepatic omentum extends from the lesser curvature of the stomach to the hilum of the spleen and the groove of the venous ligament. The esophagus is located immediately to the left of the quadrate lobe, between the lower thoracic aorta posteriorly (behind the crura of the diaphragm) and the lateral segment of the left lobe of the liver anteriorly. The cone-shaped edge of the left lobe protrudes above the cardia of the stomach, reaching the anterior border of the spleen. The fourth section of the duodenum goes obliquely upward between the body of the pancreas in front (removed) and the aorta (removed) behind.

On the lower surface of the liver there is a deep central transverse groove formed by its gate (Fig. 10). The common bile duct, hepatic artery and portal vein - the main anatomical structures of the portal - are adjacent to the right side of the groove, and their branches go to the left side, located for a considerable distance outside the hepatic tissue. The plane drawn along the gall bladder bed and the inferior vena cava mainly separates the left and right lobes of the liver (the caudate lobe extends on both sides).

Near the end of the portal groove on the left side, the round ligament of the liver (a remnant of the umbilical vein) passes through a small depression. The extrahepatic portion of the round ligament below the umbilical notch lies along the free edge of the falciform ligament. From the left end of the portal, a groove of the venous ligament stretches obliquely posteriorly, which runs from the left branch of the portal vein to the inferior vena cava near the diaphragm. The hepatogastric omentum extends from the same groove, continuing to the porta hepatis and surrounding the main portal structures in the form of the hepatoduodenal ligament.

Between the omentum and the inferior vena cava is the caudate lobe of the liver. The caudate and right lobes are connected by a narrow isthmus - the caudate process, lying between the gate and the vena cava. It is the roof of the omental opening connecting the omental bursa and the abdominal cavity. The anterior edge of this opening is the hepatoduodenal ligament, and the posterior edge is the vena cava. The inferior inversion of the parietal peritoneum onto the liver crosses the inferior vena cava immediately inferior to the liver and partially follows the depression of the right adrenal gland on the inferior surface of the right lobe.

It is important for the laparoscopist surgeon to know the segmental structure of the liver (shown in the oblique caudal plane, Fig. 11). Knowledge of the normal anatomy of the bile ducts (which occurs in 70% of cases) is necessary to recognize possible anomalies, identify ductal branches that are not visualized on cholangiograms (due to damage or obstruction), and be more careful about the anatomical structures adjacent to the gallbladder bed. Each biliary segment contains the bile duct, a branch of the portal vein and a branch of the hepatic artery. The hepatic veins run between the segments.

The right and left lobes of the liver are separated by a plane passing through the gall bladder bed and the fossa of the inferior vena cava, and each lobe is divided into two segments. The median hepatic vein is located at the junction of both lobes. The right lobe is divided by an oblique transverse plane, running correspondingly to the right hepatic vein, into anterior and posterior segments. The left hepatic vein divides the left lobe into medial and lateral segments. Each of these large segments consists of an upper and lower part.

The caudate lobe, located behind the upper part of the medial segment, is in contact to varying degrees with both lobes. The terminal sections of the hepatic artery and portal vein are anastomosed with the initial sections of the hepatic vein at the level of the hepatic lobules. Portal vessels and ducts enter each segment from the side of the centrally located gate. The gallbladder bed is formed by the inferior surfaces of the right anterior and left medial segments, and the ducts and vessels passing through these segments are at risk of damage when cholecystectomies are performed.

The cholangiogram shows the normal structure of the biliary system (Fig. 12 A). The right and left hepatic ducts join at the porta hepatis to form the common bile duct (in 90% of cases outside the liver itself). The right hepatic duct is formed by the fusion of the anterior and posterior segmental ducts, which occurs close (~1 cm) to the junction of the right and left hepatic ducts.

The right anterior segmental duct is shorter and located below the posterior segmental duct. The frontal cholangiogram shows that the bifurcation site of the anterior duct is more medial than the posterior duct. In about a third of individuals, there is a subvesical duct, which passes close to the gallbladder bed and drains into the right anterior duct. Unlike other bile ducts, it is not accompanied by a branch of the portal vein. It is not connected to the gallbladder, but can be damaged during cholecystectomy.

The left lateral superior and inferior ducts usually join at or slightly to the right of the left segmental sulcus. Bile flows into the long and thin superior duct from the apex of the left lobe, which passes into the fibrous process. In a small number of people (= 5%), the bile ducts in this appendage may persist and be a source of bile leakage when the appendage is divided to mobilize the left triangular ligament of the liver.

From the upper and lower parts of the medial segment of the left lobe, bile flows into four small ducts. When the medial and lateral segmental ducts join near the porta hepatis, the left hepatic duct is formed. Bile from the caudate part of the medial segment goes in three directions. From the rightmost section, bile usually flows into the right ductal system, from the leftmost section into the left, and from the intermediate section, with approximately equal frequency, into one of the sides.

There are several options for the location of the bile ducts inside the liver. Typically, the main left and right bile ducts join at the center of the porta hepatis (in 10% of cases, within the hepatic parenchyma). In approximately 22% of individuals, the right posterior segmental duct can cross the interlobar fissure and empty into the left hepatic duct (Fig. 12 B).

In 6% of cases, the right anterior segmental duct passes to the left side (Fig. 12 B). If the right segmental ducts are located separately, they may be damaged during cholecystectomy. It is more correct to call these ducts aberrant than accessory, since they collect bile from normal areas of the liver, and are not some kind of additional ones. On the left side, in a quarter of cases, the duct of the medial segment flows into the lower branch of the duct of the lateral segment (Fig. 12 D).

Of the peripheral ducts, the right posterior superior duct has the most consistent location. The remaining subsegmental ducts in 22% of cases have alternative drainage options.

The course of the portal vein trunks when viewed from below corresponds to the segmental structure of the liver (Fig. 13). The portal vein divides outside the liver, near the right side of the portal, and the longer left trunk crosses the portal groove. The right trunk runs close posterior to the infundibular portion of the gallbladder and is most often damaged at this location. The right trunk of the portal vein usually divides into anterior and posterior branches, going to the two main segments of the right lobe in an anterosuperior and posteroinferior direction, respectively. Sometimes this division occurs at the site of the main bifurcation of the portal vein, which thus becomes a trifurcation. During cholecystectomy, the right trunk of the portal vein may be damaged near the porta hepatis.

The left trunk of the portal vein bends anteriorly and enters the liver parenchyma in the region of the groove of the round ligament. It then divides into two branches going to the medial and lateral segments of the left lobe. Each segmental branch feeds the upper and lower sections of its segment. Proximal branches from the main right and left trunks of the portal vein extend to the caudate lobe. Some venous outflow from the gallbladder goes into the right portal trunk, but the main amount of blood flows directly into the hepatic bed of the gallbladder.

Wind G.J.
Applied laparoscopic anatomy: abdominal cavity and pelvis