Hepatic lobule: structure and function

The liver is the largest gland, the vital organ of man, without which our existence is impossible. Like all other systems of the body, it consists of smaller components. In this organ such element is the hepatic lobe. We will discuss it in detail in this article.

What is a hepatic lobule?

PD is the smallest morphological unit of the hepatic parenchyma. Visually has a prismatic shape. In its corners you can see the so-called portal, portal channels. There are five elements in them:

• Vienna interlobular.
• Artery interlobular.
• Bile ducts in the hepatic lobe.
• The portal vein branch.
• The branch of the hepatic artery.
• Nerve fibers.
• A number of lymphatic vessels.

More on the structure of the lobule, we'll talk further.

Structure of the structural segment of the liver

The components of the lobules, in turn, are hepatocytes, specific polygonal cells of the liver. They are quite big sizes - 15-30 microns. The fifth part of them is dual-core, 70% - single-core with tetraploid set, the rest have a 4- or 8-fold diploid chromosome set.

Hepatocytes form hepatic plates, bounded by sinusoidal hepatic capillaries. In the hepatic lobe such plates have a thickness of one layer of hepatocytes. They are necessarily limited to endothelial cells and cells of the hepatic sinusoids of Kupfer.

Considering the structure of the hepatic lobule, we see that these plates arise from a number of hepatocytes, which limit the lobule from the side of the stroma, namely, the limiting plates. Having examined the last anatomical atlas, we will notice that they are covered with a large number of holes. It is through them that the blood capillaries enter the lobule, forming a hepatic sinusoidal capillary network.

Hepatic plates and sinusoidal capillaries converge to the vector of the central vein passing through the organ.

Blood supply to the lobule: functional circulation

The blood supply to the liver lobe and the entire organ is organized as follows.

Functional circulation( 80% of total volume of passing volume of blood).The portal vein is divided into inter-branch branches. Those, in turn, branch into interlobular, passing through the portal channels. Interlobular branches diverge at short intervals to short perpendicular branches. They are called interlobular( input) venules. They cover the whole segment of the hepatic lobule.

Venous capillaries emerge from interlobular venules and veins to the surface of the lobule. It is through them that the blood passes through the holes in the limiting plates into the sinusoidal capillaries of the liver. Further, it circulates between the hepatic plates and collects in the central vein.

From the CV, the blood is transferred to the sub-venous vein, from which it enters the collection. Eventually, it expires in the hepatic veins.

The role of the described functional circulation is as follows:

• Delivery of nutrient absorbed substances from the digestive system, spleen, pancreas to liver segments.
• Transformation and accumulation of metabolites.
• Neutralization and removal of toxic substances.

Blood supply of the lobule: feeding circulation

The feeding circulation of the hepatic lobe accounts for 20% of the total volume of blood passing through the segment.

The branches of the interlobar and hepatic artery divide into smaller branches - interlobular arteries, whose path also lies through the portal channels. In turn, they are divided into arterial capillaries. The latter supply fresh, oxygenated blood gate channels, bile ducts, stroma of the organ.

The next stage of the blood is collected in the capillary web, which is formed by the entrance veins and interlobular veins. However, a small part of it( with the predominant part of the interlobular arteries) enters the sinusoidal capillaries. This helps to increase the oxygen content in the venous blood rotating in the hepatic sinuses.

Gateway

The gateway is a round or triangular space that can be seen in the corners of the liver lobe. VC is filled with a connective, loose tissue in which fibrocytes, fibroblasts, and wandering cells are located.

Through each channel pass:

• Bile duct.
• Interlobular vein and artery.
• Lymphatic vessels.
• Nerve fibers.

Let's talk about each of the units presented in detail.

Blood supply to the portal channel

The blood supply of this part of the lobar parenchyma is represented by the interlobular artery and the vein.

From the interlobular vein, the capillary vessels that penetrate the limiting plate depart, from which further to the hepatic lobule in the form of sinusoids. The lateral branches of the vein, located relatively perpendicular to it, - the entrance veins also turn into capillaries, becoming sinusoidal, with visible red blood cells.

The interlobular artery here is muscular, smaller in diameter than the vein. It also branches off capillaries that supply both the connective tissue of the gateway and its contents. Part of the arterial branches is formed mainly in the sinusoidal capillaries.

Capillaries from the arteries surround the bile duct, forming at the same time into the vascular periembiliary plexus.

Arterial and venous capillaries here have a similar structure. Hepatic sinusoids are actually sinusoidal capillaries. They pass between the liver plates so that their endothelium is separated from the plate only by the narrow Disse space - the perisinusoidal slit.

In the areas of bifurcations of the vessels of the hepatic sinusoids, specialized macrophages, called Cooper cells, are located in a chaotic order. In the wide areas of the Disses slots there are ITO cells, fat-containing or perinosinoid.

Bile ducts of the

canal The bile ducts in the liver segments are always located between the hepatocyte bodies and pass through the middle part of the hepatic plate.

Terminal bile ducts, distinguished by the fact that they are very short, have received the name of Herring's channels. Lined with a small number of flat cells. It becomes visible Herring's channels only at the level of the limiting plate.

These terminal bile ducts exit already into the full bile ducts, which, passing through the portal channel, pour into the interlobular duct of bile. In the anatomical atlas they are visible on the dissected liver plate as small holes.

Lymphatic and nervous system of the gated channel

Initial lymphocapillaries blindly begin inside the portal channel. Then, having already separated from the restricting plate by a narrow slit called the Mull space, they form into the lymphatic vessels. It should be noted that there are no interlobular ones among them.

Nerve fibers of the adrenergic type are accompanied by blood vessels, innervating the portal channel itself. Then, passing into the hepatic lobule, they form inside the inner-lobed spider web. Nerve fibers of the cholinergic type also enter the lobule.

Functions of the lobule

Functions of the hepatic lobes are also functions of the entire liver, as it is the constituent segment of this large gland. The spectrum of tasks of the organ, as well as its components, is very wide. We will touch on the main, most important functions for the body:

• Protection - activation of hepatic lymphocytes.
• Metabolism of active biological substances, exchange of mineral elements.
• Participation in pigmented metabolism. It manifests itself in the capture of bilirubin and the excretion of bilirubin together with bile.
• Carbohydrate metabolism. Participation in the process involves the formation and subsequent oxidation of glucose, as well as the synthesis and decomposition of glycogen.
• Synthesis of bile, bile acids, triglycerides, phospholipids. All these elements are involved in both the digestive process and fat metabolism.
• Synthesis of a wide range of proteins required for the life of the whole organism - coagulation factors, albumins and so on.
• The most important is a purifying detoxification function. It is the liver - the main organ, which cleans the entire body of toxins. Through the portal vein into the segments of the liver from the digestive tract get harmful, foreign substances, products of metabolism. In this body, they are further neutralized, and then removed from the body.

The hepatic lobe is a constituent of the body of the liver. The organ has a complex structure. Through its portal channels pass blood supply segment capillaries, lymphatic vessels, bile ducts and nerve endings. The basis of the lobule is a special liver cells - hepatocytes, which have their own unique structure. The functions of both the whole liver and its lobules are similar.