Blood supply and innervation of the liver

Intraorgan vascular systems and segmental division

Two isolated vascular networks are distinguished in the liver tissue. The first of these is the portal (Glissonian) system. It combines the branches of the portal vein, hepatic artery, and biliary tract. The course of these elements within the parenchyma largely coincides, and the bundles themselves penetrate the organ from the direction of the porta hepatis.

The second network is called the caval system and is represented by the hepatic veins. It is important to note that the direction of these vessels does not coincide with the course of the elements of the portal system.

Modern surgical anatomy is based specifically on the branching of the portal system, as this is the most justified approach for surgical interventions. The classification by Couinaud (1957) is universally accepted. According to it, the organ is divided into 2 lobes (right and left), which include 5 sectors and 8 segments. A segment or sector is understood as a discrete area of tissue with independent blood flow, bile outflow, and lymph drainage. Within the thickness of the parenchyma, the segments are grouped radially around the porta hepatis.

Arterial bed

The main source of arterial blood is the proper hepatic artery (a. hepatica propria). It is a direct continuation of the common hepatic artery (a. hepatica communis), which originates from the celiac trunk (truncus celiacus).

The course of the vessel is as follows: the common hepatic artery runs along the upper margin of the head of the pancreas to the hepatoduodenal ligament (lig. hepatoduodenale). There it divides into the gastroduodenal (a. gastroduodenalis) and proper hepatic arteries. The a. hepatica propria ascends within the ligament toward the porta hepatis. Topographically, it is located anterior to the portal vein and to the left of the hepatic duct.

At the porta hepatis, the proper hepatic artery (its length is 0.5–3 cm) divides into lobar arteries:

• Left branch (a. hepatica lobaris sinistra): supplies the left, quadrate, and caudate lobes. It has a length of 2–3 cm and a diameter of 2–3 mm.
• Right branch (a. hepatica lobaris dextra): larger than the left. It supplies the right lobe and gives off the cystic artery (a. cystica) to the gallbladder.

Sometimes a third branch departs from the trunk, supplying the quadrate lobe. In its initial section, the a. hepatica propria also gives off the right gastric artery (a. gastrica dextra). Clinically important: ligation of a lobar branch causes necrosis of the corresponding area of the liver, which is extremely dangerous for the patient's life.

Venous system

The venous bed of the liver has a clear division into inflow and outflow:

1. Inflow is provided by the portal vein system, which collects and brings blood from the abdominal organs.
2. Outflow (efferent system) is carried out through the hepatic veins (vv. hepaticae). They drain blood directly into the inferior vena cava (v. cava inferior).

The number of hepatic veins can vary, but most often three permanent trunks are formed: the right, left, and middle. They empty into the inferior vena cava just below the tendinous center of the diaphragm. The area where the inferior vena cava passes through the parenchyma and the points of entry of the hepatic veins are called the second (caval) porta of the liver. In the area where the veins empty, the inferior vena cava forms an ampullary dilatation, which creates an increased risk of its injury during surgical mobilization.

Innervation and lymphatic system

Nervous regulation of the organ is provided by the hepatic plexus. It is formed by branches of the vagus nerves (n. vagus), the celiac plexus, and the inferior phrenic plexus. A special role is played by branches of the right phrenic nerve, which run along the inferior vena cava and penetrate through the coronary ligament. They are responsible for the afferent (sensory) innervation of the liver and gallbladder. This is precisely why phrenic sign — radiation of pain into the right supraclavicular region — occurs in diseases of the hepatobiliary zone.

The lymphatic system is represented by intra- and extraorgan plexuses.

• From the visceral surface, lymph collects into large trunks running along the portal vein to the lymph nodes of the lesser omentum.
• From the diaphragmatic surface and from the deep layers (around the hepatic veins), efferent vessels run together with the inferior vena cava to regional nodes above the diaphragm.

Some vessels pierce the diaphragm and drain directly into the thoracic duct and posterior mediastinal nodes. There are connections between the hepatic and celiac lymph nodes, allowing bidirectional lymph flow. Although there are no direct anastomoses between the lymphatic pathways of the liver and the stomach, their efferent vessels drain into common regional lymph nodes.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Topography of the elements of the hepatoduodenal ligament
• Anatomy of the epiploic foramen and omental bursa
• Branching of the common hepatic artery and collateral circulation
• Ligamentous apparatus of the liver (coronary ligament) and its relation to vessels

Other topics in the section "Topographic Anatomy of the Abdomen"

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