home Diseases What type of anastomosis are the hepatic veins? Features of the blood supply to the liver. How does the blood supply to the liver structures occur?

What type of anastomosis are the hepatic veins? Features of the blood supply to the liver. How does the blood supply to the liver structures occur?

The liver is a vital exocrine gland in humans. Its main functions include neutralizing toxins and removing them from the body. In case of liver damage, this function is not performed and harmful substances enter the blood. With the bloodstream they flow through all organs and tissues, which can lead to serious consequences.

Since there are no nerve endings in the liver, a person may not even suspect that there is any disease in the body for a long time. In this case, the patient goes to the doctor too late, and then treatment no longer makes sense. Therefore, it is necessary to carefully monitor your lifestyle and undergo regular preventive examinations.

Anatomy of the liver

According to the classification, the liver is divided into independent segments. Each is connected to a vascular inflow, outflow and bile duct. In the liver, the portal vein, hepatic artery and bile duct are divided into branches, which in each segment are collected into veins.

The organ consists of afferent and efferent blood vessels. The main afferent vein functioning in the liver is the portal vein. The drainage veins include the hepatic veins. Sometimes there are cases when these vessels independently flow into the right atrium. Basically, the veins of the liver flow into the inferior vena cava.

The permanent venous vessels of the liver include:

right vein;
middle vein;
left vein;
vein of the caudate lobe.

Portal

The portal vein of the liver is a large vascular trunk that collects blood that passes through the stomach, spleen and intestines. After collection, it delivers this blood to the lobes of the liver and transfers the already purified blood back into the general channel.

Normally, the length of the portal vein is 6-8 cm, and its diameter is 1.5 cm.

This blood vessel originates behind the head of the pancreas. Three veins merge there: the inferior mesenteric vein, the superior mesenteric vein and the splenic vein. They form the roots of the portal vein.

In the liver, the portal vein divides into branches that diverge throughout all hepatic segments. They accompany the branches of the hepatic artery.

The blood carried by the portal vein saturates the organ with oxygen and delivers vitamins and minerals to it. This vessel plays an important role in digestion and detoxifies the blood. If the functioning of the portal vein is disrupted, serious pathologies arise.

Diameter of hepatic veins

The largest of the liver vessels is the right vein, the diameter of which is 1.5-2.5 cm. Its flow into the inferior cava occurs in the area of its anterior wall near the hole in the diaphragm.

Normally, the hepatic vein, formed by the left branch of the portal vein, enters at the same level as the right one, only on the left side. Its diameter is 0.5-1 cm.

The diameter of the vein of the caudate lobe in a healthy person is 0.3-0.4 cm. Its mouth is located slightly below the place where the left vein flows into the inferior vena cava.

As you can see, the sizes of the hepatic veins differ from each other.

The right and left ones, passing through the liver, collect blood from the right and left hepatic lobes, respectively. The middle and vein of the caudate lobe are from the lobes of the same name.

Hemodynamics in the portal vein

According to an anatomy course, arteries pass through many organs of the human body. Their function is to saturate the organs with the substances they need. Arteries bring blood to the organs, and veins remove it. They transport processed blood to the right side of the heart. This is how the systemic and pulmonary circulation works. The hepatic veins play a role in it.

The gate system functions specifically. The reason for this is its complex structure. From the main trunk of the portal vein, many branches branch off into venules and other bloodstreams. That is why the portal system, in fact, constitutes another additional circle of blood circulation. It purifies blood plasma from harmful substances such as breakdown products and toxic components.

The portal vein system is formed as a result of the union of large vein trunks near the liver. From the intestine, blood is carried by the superior mesenteric and inferior mesenteric veins. The splenic vessel emerges from the organ of the same name and receives blood from the pancreas and stomach. It is these large veins, merging, that become the basis of the crow vein system.

Near the entrance to the liver, the trunk of the vessel, dividing into branches (left and right), diverges between the lobes of the liver. In turn, the hepatic veins are divided into venules. A network of small veins covers all lobes of the organ inside and out. Once contact between blood and soft tissue cells occurs, these veins will carry blood into the central vessels that emerge from the middle of each lobe. After this, the central venous vessels unite into larger ones, from which the hepatic veins are formed.

liver blockage?

Hepatic vein thrombosis is a liver pathology. It is caused by a violation of internal circulation and the formation of blood clots that block the outflow of blood from the organ. Official medicine also calls it Budd-Chiari syndrome.

Thrombosis of the hepatic veins is characterized by partial or complete narrowing of the lumens of blood vessels, resulting from the impact of a blood clot. Most often it occurs in those places where the mouth of the liver vessels is located and they flow into the vena cava.

If there are any obstructions in the liver to the outflow of blood, the pressure in the blood vessels increases and the hepatic veins dilate. Although the blood vessels are very elastic, too much pressure can cause them to rupture, resulting in internal bleeding and possibly death.

The question of the origin of hepatic vein thrombosis is still not closed. Experts on this issue are divided into two camps. Some consider hepatic vein thrombosis to be an independent disease, while others argue that it is a secondary pathological process caused as a result of complications of the underlying disease.

The first case includes thrombosis, which occurred for the first time, that is, we are talking about Budd-Chiari disease. The second case includes Budd-Chiari syndrome, which manifested itself due to a complication of the primary disease, which is considered the main one.

Due to the difficulty in separating measures for diagnosing these processes, the medical community usually calls liver circulatory disorders not a disease, but a syndrome.

Causes of hepatic vein thrombosis

Blood clots in the liver occur due to:

Protein S or C deficiency.
Antiphospholipid syndrome.
Changes in the body associated with pregnancy.
Long-term use of oral contraceptives.
Inflammatory processes occurring in the intestines.
Connective tissue diseases.
Various peritoneal injuries.
The presence of infections - amoebiasis, hydatid cysts, syphilis, tuberculosis, etc.
Tumor invasions of the liver veins - carcinoma or renal cell carcinoma.
Hematological diseases - polycythemia, paroxysmal nocturnal hemoglobinuria.
Hereditary predisposition and congenitality of hepatic vein defects.

The development of Budd-Chiari syndrome usually lasts from several weeks to months. Against this background, cirrhosis and portal hypertension often develop.

Symptoms

If unilateral hepatic obstruction has developed, no special symptoms are observed. directly depends on the stage of development of the disease, the location where the blood clot formed, and the complications that arise.

Often, Budd-Chiari syndrome is characterized by a chronic form, which is not accompanied by symptoms for a long time. Sometimes signs of hepatic thrombosis can be detected by palpation. The disease itself is diagnosed solely as a result of instrumental research.

Chronic blockage is characterized by symptoms such as:

Mild pain in the right hypochondrium.
Feeling of nausea, sometimes accompanied by vomiting.
Change in skin color - yellowing appears.
The sclera of the eyes turn yellow.

The presence of jaundice is not necessary. In some patients it may be absent.

Symptoms of acute blockage are more obvious. These include:

Sudden onset of vomiting, in which blood gradually begins to appear as a result of a rupture in the esophagus.
Severe pain that is epigastric in nature.
A progressive accumulation of free fluids in the peritoneal cavity, which occurs due to venous stagnation.
Sharp pain throughout the abdomen.
Diarrhea.

In addition to these symptoms, the disease is accompanied by an enlargement of the spleen and liver. Acute and subacute forms of the disease are characterized by liver failure. There is also a fulminant form of thrombosis. It is extremely rare and dangerous because all the symptoms develop very quickly, leading to irreparable consequences.

Diagnosis of blockage of hepatic vessels

Budd-Chiari syndrome is characterized by a clear clinical picture. This greatly facilitates the diagnosis. If the patient has an enlarged liver and spleen, there are signs of fluid in the peritoneal cavity, and laboratory tests indicate elevated blood clotting rates, first of all, the doctor begins to suspect the development of thrombosis. However, he is obliged to carefully study the patient's medical history.

Significant reasons to suspect thrombosis in a patient include the following signs:

In addition to the fact that the doctor studies the medical history and conducts a physical examination, the patient needs to donate blood for a general and biochemical analysis, as well as for coagulation. You also need to take a liver test.

To accurately make a diagnosis, the following examination methods are used:

ultrasound examination;
X-ray of the portal vein;
contrast study of blood vessels;
computed tomography (CT);
magnetic resonance imaging (MRI).

All these studies make it possible to assess the degree of enlargement of the liver and spleen, the severity of vascular damage, and detect the location of the blood clot.

Complications

If a patient contacts a doctor late or changes resulting from thrombosis are diagnosed late, the risk of complications increases. These include:

liver failure;
portal hypertension;
hepatocellular carcinoma;
ascites;
encephalopathy;
bleeding from the dilated hepatic vein;
porosystemic collateralization;
mesenteric thrombosis;
peritonitis, which is bacterial in nature;
liver fibrosis.

Treatment

In medical practice, two methods of treating Budd-Chiari syndrome are used. One of them is medicinal, and the second is through surgery. The disadvantage of medications is that it is impossible to recover completely with their help. They give only short-term effect. Even if the patient promptly consults a doctor and is treated with medications, without the intervention of a surgeon, almost 90% of patients die within a short period of time.

The main goal of therapy is to eliminate the underlying causes of the disease and, as a result, restore blood circulation in the area affected by thrombosis.

Drug therapy

In order to remove excess fluid from the body, doctors prescribe medications with a diuretic effect. To prevent further development of thrombosis, the patient is prescribed anticoagulants. Corticosteroids are used to relieve abdominal pain.

In order to improve blood characteristics and accelerate the resorption of formed blood clots, fibrinolytics and antiplatelet agents are used. In parallel, maintenance therapy is carried out aimed at improving metabolism in liver cells.

Surgical therapy

Conservative treatment methods for a diagnosis associated with thrombosis cannot provide the necessary result - restoration of normal circulation in the affected area. In this case, only radical methods will help.

Establish anastomoses (artificial synthetic connections between vessels that allow blood circulation to be restored).
Place a prosthesis or mechanically dilate a vein.
Place a shunt to reduce blood pressure in the portal vein.
Liver transplant.

In the case of a fulminant course of the disease, practically nothing can be done. All changes happen very quickly, and doctors simply do not have time to take the necessary measures.

Prevention

All measures to prevent the development of Budd-Chiari syndrome are reduced to the fact that you need to regularly visit medical institutions in order to undergo the necessary diagnostic procedures as a preventive measure. This will help to promptly detect and begin treatment of hepatic vein thrombosis.

There are no special preventive measures for thrombosis. There are only measures to prevent relapse of the disease. These include taking blood thinning anticoagulants and undergoing examinations every 6 months after surgery.

The hepatic artery is a branch of the celiac trunk. It passes along the upper edge of the pancreas to the initial part of the duodenum, then goes up between the leaves of the lesser omentum, located in front of the portal vein and medial to the common bile duct, and at the porta hepatis it divides into right and left branches. Its branches also include the right gastric and gastroduodenal arteries. Additional branches are often found. Topographic anatomy has been carefully studied on donor livers. With abdominal trauma or catheterization of the hepatic artery, its dissection is possible. Embolization of the hepatic artery sometimes leads to the development of gangrenous cholecystitis.

Clinical manifestations

The diagnosis is rarely made while the patient is alive; There are few works describing the clinical picture. Clinical manifestations are associated with an underlying disease, for example, bacterial endocarditis, periarteritis nodosa, or are determined by the severity of upper abdominal surgery. Pain in the epigastric region on the right occurs suddenly and is accompanied by shock and hypotension. There is pain on palpation of the right upper quadrant of the abdomen and the edge of the liver. Jaundice increases rapidly. Typically, leukocytosis, fever, and biochemical blood tests reveal signs of cytolytic syndrome. Prothrombin time increases sharply, bleeding appears. When large branches of the artery are occluded, a coma develops and the patient dies within 10 days.

It is necessary to carry out hepatic arteriography. It can be used to detect hepatic artery obstruction. Intrahepatic collaterals develop in the portal and subcapsular areas. Extrahepatic collaterals with neighboring organs are formed in the ligamentous apparatus of the liver [3].

Scanning.Infarctions are usually round or oval, occasionally wedge-shaped, located in the center of the organ. In the early period, they are detected as hypoechoic foci during ultrasound examination (ultrasound) or poorly demarcated areas of reduced density on computed tomograms that do not change with the introduction of a contrast agent. Later, heart attacks look like confluent foci with clear boundaries. Magnetic resonance imaging (MRI) allows you to identify infarcts as areas with low signal intensity on T1-weighted images and with high intensity on T2-weighted images. With large infarcts, the formation of “lake” of bile, sometimes containing gas, is possible.

Treatment should be aimed at eliminating the cause of the damage. To prevent secondary infection during liver hypoxia, antibiotics are used. The main goal is the treatment of acute hepatocellular failure. In case of arterial injury, percutaneous embolization is used.

Damage to the hepatic artery during liver transplantation

When the bile ducts are damaged due to ischemia, they speak of ischemic cholangitis.It develops in patients who have undergone liver transplantation due to thrombosis or stenosis of the hepatic artery or occlusion of the paraductal arteries |8[. Diagnosis is complicated by the fact that the picture when examining biopsy specimens may indicate obstruction of the bile ducts without signs of ischemia.

After liver transplantation, hepatic artery thrombosis is detected using arteriography. Doppler examination does not always reveal changes; moreover, correct assessment of its results is difficult [b]. The high reliability of spiral CT has been shown.

Hepatic artery aneurysms

Hepatic artery aneurysms are rare and account for one fifth of all visceral vessel aneurysms. They may be a complication of bacterial endocarditis, periarteritis nodosa, or arteriosclerosis. Among the causes, the role of mechanical damage is increasing, for example due to road traffic accidents or medical interventions such as biliary tract surgery, liver biopsy and invasive X-ray examinations. False aneurysms occur in patients with chronic pancreatitis and pseudocyst formation. Hemobilia is often associated with false aneurysms. Aneurysms are congenital, intra- and extrahepatic, ranging in size from the head of a pin to a grapefruit. Aneurysms are identified by angiography or discovered incidentally during surgery or autopsy.

Clinical manifestations varied. Only a third of patients have the classic triad: jaundice |24|, abdominal pain and hemobilia. A common symptom is abdominal pain; the period from their appearance to the rupture of the aneurysm can reach 5 months.

In 60-80% of patients, the reason for the initial visit to the doctor is the rupture of a modified vessel with the leakage of blood into the abdominal cavity, biliary tract or gastrointestinal tract and the development of hemoperitoneum, hemobilia or hematemesis.

Ultrasound allows you to make a preliminary diagnosis; it is confirmed using hepatic arteriography and contrast-enhanced CT (see Fig. 11-2). Pulsed Doppler ultrasound can detect turbulence of blood flow in the aneurysm.

Treatment. For intrahepatic aneurysms, vessel embolization is used under angiography control (see Fig. 11-3 and 11-4). In patients with aneurysms of the common hepatic artery, surgical intervention is necessary. In this case, the artery is ligated above and below the site of the aneurysm.

Hepatic arteriovenous fistulas

Common causes of arteriovenous fistulas are blunt trauma to the abdomen, liver biopsy or tumors, usually primary liver cancer. Patients with hereditary hemorrhagic telangiectasia (Randu-Weber-Osler disease) have multiple fistulas, which can lead to congestive heart failure.

If the fistula is large, a murmur can be heard over the right upper quadrant of the abdomen. Hepatic arteriography can confirm the diagnosis. Embolization with gelatin foam is usually used as a therapeutic measure.

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.

Liver arteries

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:

Equity.
Segmental.
Interlobular.
Around lobular.

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:

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.

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

The blood supply to the liver directly affects the quality of the functions performed by the organ. The process is carried out using a system of arteries and veins connecting the liver with other organs. Blood enters through two vessels and is distributed throughout the organ through branches of the left and right lobes.

Impaired tissue circulation deprives the liver of important nutrients and oxygen. The body's main filter does not perform the detoxification function well. As a result, the entire body suffers and overall health is impaired.

Venous blood, containing a mass of toxic substances, moves towards the liver from the intestines. It enters the liver directly through the portal vein. Next, there is a division into small interlobular veins.

Arterial blood enters the liver through the hepatic artery, which also branches into smaller interlobular arteries. Interlobular vessels of both types push blood into the sinusoids. There is mixed blood flow. It then drains into the central vein, and from there into the hepatic and inferior vena cava.

Liver circulation diagram

The liver, as a parenchymal organ, that is, an organ that does not have cavities, in its anatomy consists of structural units - lobules. Each lobule is formed by hepatocytes - specific cells. The prismatic lobules unite to form the right and left lobes of the liver. Blood supply is carried out directly by the system of arteries, veins, and connecting vessels.

The peculiarity of the blood supply to the liver is that the organ receives not only arterial blood, like all other internal organs, but mostly venous. The arteries supply nutrients and oxygen. And the veins carry blood for subsequent detoxification.

At an average blood flow rate of 100 ml per second, the blood supply is considered normal. As blood pressure changes, the speed changes. The smooth operation of arteries and veins helps regulate blood supply. In diseases of the biliary system, there is often a high blood flow rate in the portal vein and low blood flow in the arteries.

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. hepatitis; 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. hepatitis; 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.

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.

Blood supply to the liver

The blood supply to the liver is carried out by a system of arteries and veins, which are connected to each other and to the vessels of other organs. This organ performs a huge number of functions, including the detoxification of toxins, the synthesis of proteins and bile, and the storage of many compounds. Under conditions of normal blood circulation, it does its job, which has a positive effect on the condition of the whole organism.

How do blood circulation processes occur in the liver?

The liver is a parenchymal organ, that is, it does not have a cavity. Its structural unit is a lobule, which is formed by specific cells, or hepatocytes. The lobule has the shape of a prism, and neighboring lobules are combined into lobes of the liver. The blood supply to each structural unit is carried out using the hepatic triad, which consists of three structures:

Main arteries of the liver

Arterial blood enters the liver from vessels that originate from the abdominal aorta. The main artery of the organ is the hepatic one. Along its length, it gives blood to the stomach and gall bladder, and before entering the gate of the liver or directly in this area, it is divided into 2 branches:

the left hepatic artery, which carries blood to the left, quadrate and caudal lobes of the organ;
the right hepatic artery, which supplies blood to the right lobe of the organ and also gives off a branch to the gallbladder.

The arterial system of the liver has collaterals, that is, areas where neighboring vessels are united through collaterals. These may be extrahepatic or intraorgan associations.

Large and small veins and arteries take part in the blood circulation of the liver

Veins of the liver

The veins of the liver are usually divided into afferent and efferent. Along the afferent tract, blood moves to the organ, and along the efferent tract, it moves away from it and carries away the final products of metabolism. Several main vessels are associated with this organ:

portal vein - an afferent vessel that is formed from the splenic and superior mesenteric veins;
hepatic veins are a system of drainage tracts.

The portal vein carries blood from the organs of the digestive tract (stomach, intestines, spleen and pancreas). It is saturated with toxic metabolic products, and their neutralization occurs in the liver cells. After these processes, the blood leaves the organ through the hepatic veins, and then participates in the systemic circulation.

Diagram of blood circulation in the liver lobules

The topography of the liver is represented by small lobules, which are surrounded by a network of small vessels. They have structural features that help cleanse the blood of toxic substances. When entering the portal of the liver, the main afferent vessels are divided into small branches:

equity,
segmental,
interlobular,
intralobular capillaries.

These vessels have a very thin muscle layer to facilitate blood filtration. At the very center of each lobule, the capillaries merge into a central vein, which is devoid of muscle tissue. It flows into the interlobular vessels, and they, accordingly, into the segmental and lobar collecting vessels. Leaving the organ, the blood is distributed through 3 or 4 hepatic veins. These structures already have a full muscle layer and carry blood into the inferior vena cava, from where it enters the right atrium.

Portal vein anastomoses

The blood supply to the liver is adapted to ensure that the blood from the digestive tract is cleared of metabolic products, poisons and toxins. For this reason, stagnation of venous blood is dangerous for the body - if it collects in the lumen of blood vessels, toxic substances will poison the person.

Anastomoses are bypass routes for venous blood. The portal vein is connected to the vessels of some organs:

If for some reason the fluid cannot enter the liver (due to thrombosis or inflammatory diseases of the hepatobiliary tract), it does not accumulate in the vessels, but continues to move along bypass routes. However, this condition is also dangerous because the blood does not have the opportunity to get rid of toxins and flows into the heart in an unclean form. Portal vein anastomoses begin to function fully only in pathological conditions. For example, with cirrhosis of the liver, one of the symptoms is the filling of the veins of the anterior abdominal wall near the navel.

The most important processes occur at the level of liver lobules and hepatocytes

Regulation of blood circulation processes in the liver

The movement of fluid through the vessels occurs due to the pressure difference. The liver constantly contains at least 1.5 liters of blood, which moves through large and small arteries and veins. The essence of blood circulation regulation is to maintain a constant amount of fluid and ensure its flow through the vessels.

Mechanisms of myogenic regulation

Myogenic (muscular) regulation is possible due to the presence of valves in the muscular wall of blood vessels. When muscles contract, the lumen of the blood vessels narrows and fluid pressure increases. When they relax, the opposite effect occurs. This mechanism plays a major role in the regulation of blood circulation and is used to maintain constant pressure in different conditions: during rest and physical activity, in heat and cold, with increases and decreases in atmospheric pressure and in other situations.

Humoral regulation

Humoral regulation is the effect of hormones on the condition of the walls of blood vessels. Some of the biological fluids can affect veins and arteries, expanding or narrowing their lumen:

adrenaline - binds to adrenergic receptors in the muscular wall of intrahepatic vessels, relaxes them and provokes a decrease in blood pressure;
norepinephrine, angiotensin - act on veins and arteries, increasing fluid pressure in their lumen;
acetylcholine, products of metabolic processes and tissue hormones - simultaneously dilates arteries and constricts veins;
some other hormones (thyroxine, insulin, steroids) - provoke an acceleration of blood circulation and at the same time a slowdown in blood flow through the arteries.

Hormonal regulation underlies the response to many environmental factors. The secretion of these substances is carried out by endocrine organs.

Nervous regulation

Mechanisms of nervous regulation are possible due to the peculiarities of the innervation of the liver, but they play a secondary role. The only way to influence the condition of the hepatic vessels through the nerves is to irritate the branches of the celiac nerve plexus. As a result, the lumen of the vessels narrows, the amount of blood flow decreases.

Blood circulation in the liver differs from the usual pattern that is typical for other organs. The inflow of fluid is carried out by veins and arteries, and the outflow is carried out by the hepatic veins. During circulation in the liver, the fluid is cleared of toxins and harmful metabolites, after which it enters the heart and further participates in blood circulation.

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Blood supply to the liver diagram

The liver has a dual blood supply: approximately 70% of the blood comes from the portal vein, the rest from the hepatic artery. The branches of the hepatic vein drain blood into the inferior vena cava. The functioning of the liver is based on the complex interaction of these vessels.

Depending on the course of the vessels, the liver is divided into eight segments, which is of great importance from a surgical point of view, since when choosing the type of surgical intervention, preference is often given to segmentectomy rather than lobectomy.

Segment 1 (caudal lobe) is autonomous, since it is supplied with blood from both the left and right branches of the portal vein and from the hepatic artery, while the venous outflow from this segment is carried out directly into the inferior vena cava. In Budd-Chiari syndrome, thrombosis of the main hepatic vein leads to the fact that the outflow of blood from the liver occurs entirely through the caudate lobe, which is significantly hypertrophied.

The liver is clearly visible on a plain abdominal radiograph. An appendage of the right lobe is often found, directed towards the region of the right iliac fossa - the so-called Riedel's lobe.

View of the liver from the front and bottom, showing the division into 8 segments. Segment 1 - caudate lobe. Computed tomography of the liver. An axial view through the superior fornix of the liver allows one to see the division of the hepatic parenchyma into segments.

The posterior segment of the right lobe is rarely viewed at this level, since the bulk of this segment lies below the anterior segment of the right lobe:

1 - medial segment of the left lobe of the liver; 2 - left hepatic vein; 3 - lateral segment of the left lobe of the liver;

4 - median hepatic vein; 5 - anterior segment of the right lobe of the liver; 6 - posterior segment of the right lobe of the liver;

7 - right hepatic vein; 8 - aorta; 9 - esophagus;

10 - stomach; 11 - spleen. Budd-Chiari syndrome: decreased absorption of colloid in the liver in the caudate lobe of the liver and increased absorption in the bones and spleen.

Scintigraphy using technetium. Normal abdominal radiograph showing Riedel's lobe in the right hypochondrium

The hepatic artery, portal vein and common hepatic duct are located nearby at the porta hepatis. The hepatic artery is normally a branch of the celiac trunk, while the gallbladder is supplied with blood from the cystic artery; Anatomical features of the structure of these vessels are often encountered.

There are several ways to contrast the portal vein, which forms at the confluence of the splenic and superior mesenteric veins behind the head of the pancreas.

1 - portal vein; 2 - hepatic artery; 3 - celiac trunk;

4 - aorta; 5 - splenic vein; 6 - gastroduodenal artery;

7 - superior mesenteric vein; 8 - common bile duct; 9 - gallbladder;

10 - cystic artery; 11 - hepatic ducts

The method of direct percutaneous injection into the splenic pulp (splenovenography) used to be common, but is now rarely used, even with an enlarged spleen and signs of portal hypertension. In infants with an open umbilical vein, direct catheterization with contrast of the left portal vein system is possible. Currently, selective angiography is more often used, when the portal system is visualized during catheterization of the splenic artery and subsequent observation of the venous return phase after the passage of contrast through the spleen.

In patients with portal hypertension, image quality may be poor due to hemodilution and decreased contrast agent concentrations, which can be corrected by digital subtraction angiography. Once the catheter has passed through the right atrium and ventricle, it can be inserted into the hepatic veins. In this case, it is easy to evaluate the X-ray image and measure venous pressure, for which the value of free hepatic venous pressure in the lumen of the vessel is first recorded, then the catheter is carefully immersed in the hepatic parenchyma.

The tip of the balloon expands and the measured value (fixed hepatic venous pressure) practically corresponds to the pressure in the portal vein, which allows the gradient of this parameter to be calculated. It is easiest to pass the catheter through the right internal jugular vein, since this provides almost straight-line access. A similar access technique is used for transvenous liver biopsy.

Using ultrasound of a normal liver, its size and consistency, filling defects, anatomy of the bile duct system and portal vein are assessed. The hepatic parenchyma and surrounding tissues can also be examined using computed tomography.

Ultrasound examination of anatomical structures at the porta hepatis.

The hepatic artery is located between the dilated common hepatic duct and the portal vein.

For magnetic resonance cholangiopancreatography, T1 and T2 relaxation times of the medium are used. The fluid signal has very low density (producing a dark color) on T2 images and high density (producing a light color) on T2 images. With this research method, T2 images are used to obtain cholangiograms and pancreatograms. The sensitivity and specificity of the technique vary depending on the technique and indication.

If the suspicion of pathology is small, it is better to perform magnetic resonance cholangio- and pancreatography, and if there is a high probability of surgical intervention, prefer endoscopic retrograde cholangiography. In addition, periampullary formations often go undetected due to artifacts caused by the accumulation of air in the duodenum. Unfortunately, magnetic resonance imaging is not sensitive enough for early diagnosis of bile duct pathology, for example in the case of subtle lesions often found in primary sclerosing cholangitis. The TESLA scanning method is rarely used to visualize the bile ducts.

Computer or MRI are the best methods for studying liver pathology. Thanks to contrast and imaging in the arterial and venous phases, it is possible to diagnose both benign and malignant formations. 3D computer and MRI provide images of blood vessels. With the additional use of MRC or TESLA images, biliary tract cancer can be diagnosed.

a - Magnetic resonance imaging showing a normal portal vein system. The superior mesenteric vein (shown by a short arrow) and its main branches are visible.

The portal vein (long arrow) passes further into the liver. The right lobe of the liver (R) has been identified.

b,c - On the magnetic resonance imaging (b) in the middle sagittal projection, the aorta (shown by a long arrow), the celiac trunk (short arrow) and the root of the superior mesenteric artery (arrowhead) are identified.

Contributed by Dr. Drew Torigian. TESLA scanning (c) also serves as a non-invasive method for studying the anatomy of the biliary tract:

RHD - right hepatic duct; LHD - left hepatic duct; CHD - common hepatic duct; 1 - “cystic duct” - cystic duct.

Computer or MRI can be used as the only research methods to detect tumors, describe vascular anatomy and determine the extent of bile duct damage.

Isotope scanning of the liver and spleen using 99mTc (a). HIDA scan showing normal absorption and excretion of the compound into the bile duct (b).

The study can be performed in conjunction with cholecystokinin stimulation to assess gallbladder or sphincter of Oddi dysfunction.

1 - surface markers of the chest; 2 - liver; 3 - spleen

The radioisotope method for studying the liver is currently used much less frequently. This research method determines the concentration of technetium in reticuloendotheliocytes (Kupffer cells) administered intravenously.

The laparoscopic method is rarely used for direct visual examination of the liver, but it allows biopsy to be performed under visual control, since in this case the lower surface of the organ is clearly visible.

Educational video segmental structure of the liver in the diagram

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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.

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.

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.

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 anastomoses with:

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

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

Regulation of blood supply

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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Features of blood supply to the liver

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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