The liver is the largest gland, a vital human organ, without which our existence is impossible. Like all other body systems, it consists of smaller components. In this organ, such an element is the hepatic lobule. We will analyze it in detail in this article.
What is a liver lobule?
PD is the smallest morphological unit of the hepatic parenchyma. Visually it has a prismatic shape. In its corners you can see the so-called portal, gate channels. They contain five elements:
- Interlobular vein.
- Interlobular artery.
- Bile ducts in the hepatic lobule.
- Portal vein branch.
- Hepatic artery branch.
- Nerve fibers.
- Row of lymphatic vessels.
We'll talk more about the structure of the lobule later.
Structure of the structural segment of the liver
The components of the lobule itself, in turn, are hepatocytes, specific polygonal liver cells. They are quite large in size - 15-30 microns. Fifth of thembinuclear, 70% are mononuclear with a tetraploid set, the rest have a 4- or 8-fold diploid chromosome set.
Hepatocytes form hepatic laminae bounded by sinusoidal hepatic capillaries. In the hepatic lobule, such plates have a thickness of one layer of hepatocytes. They are necessarily limited to endothelial cells and hepatic Kupffer sinusoid cells.
Considering the structure of the hepatic lobule, we see that the mentioned plates arise from a number of hepatocytes that limit the lobule from the side of the stroma, namely, the limiting plates. Having examined the latter on the anatomical atlas, we will notice that they are dotted with a large number of holes. It is through them that the blood capillaries enter the lobule, thus forming a hepatic sinusoidal capillary network.
The liver plates and sinusoidal capillaries converge to the vector of the central vein passing through the organ.
Blood supply of the lobule: functional circulation
The blood supply of the liver lobule and the entire organ is organized as follows.
Functional circulation (80% of the total share of the passing blood volume). The portal vein divides into interlobar branches. Those, in turn, branch into interlobular, passing in the portal canals. Interlobular branches at strict intervals diverge into short perpendicular branches. They are called interlobular (input) venules. They cover the entire segment of the hepatic lobule.
The lobules emerge from the interlobular venules and veins to the surfacevenous capillaries. It is with the help of them that blood passes through the holes in the limiting plates into the sinusoidal capillaries of the liver. It then circulates between the liver plates and collects in the central vein.
From the CV, the blood is transferred to the sublobular vein, from where it enters the collecting veins. Eventually, it bleeds into the hepatic veins.
The role of the described functional circulation is as follows:
- Delivery of absorbed nutrients 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: nourishing circulation
The supply circulation of the hepatic lobule accounts for 20% of the total blood volume passing through the segment.
The branches of the interlobar and hepatic arteries diverge into smaller branches - the interlobular arteries, whose path also lies through the portal canals. In turn, they are divided into arterial capillaries. The latter supply fresh, oxygenated blood to the portal ducts, bile ducts, stroma of the organ.
The next step, the blood is collected in the capillary web, which is formed by the input venules and interlobular veins. However, a small part of it (mainly from the interlobular arteries) enters the sinusoidal capillaries. This helps increase the oxygen content of the venous blood circulating in the hepatic sinuses.
Gate channel
The portal canal is a round or triangular space that can be seen at the corners of the hepatic lobule. VC is filled with loose connective tissue, in which fibrocytes, fibroblasts, 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 presented units in detail.
Blood supply of the portal canal
The blood supply to this part of the lobular parenchyma is represented by the interlobular artery and vein.
From the interlobular vein, capillary vessels depart, penetrating into the limiting plate, from where further - into the hepatic lobule in the form of already sinusoids. The lateral branches of the vein, located perpendicular to it, - the input venules also turn into capillaries, becoming sinusoidal, with erythrocytes visible.
The interlobular artery here is of a muscular appearance, smaller in diameter than a vein. Capillaries also branch off from it, supplying both the connective tissue of the portal canal and its contents. Part of the arterial branches is formed mainly into sinusoidal capillaries.
The capillaries from the arteries surround the bile duct, folding into the choroid peribiliary plexus.
Arterial and venous capillaries here have a similar structure. The hepatic sinusoids are actually sinusoidal capillaries. They pass between the plates of the liver so that their endotheliumseparated from the plate only by a narrow space of Disse - a perisinusoidal gap.
In the areas of bifurcations of the vessels of the hepatic sinusoids, specialized macrophages, called Cooper cells, are located in a chaotic manner. Wide areas of Disse's fissures contain ITO cells, fat-containing or perisinusoidal.
Bile duct channel
Bile ducts in segments of the liver are always located between the bodies of hepatocytes and pass through the middle part of the liver plate.
Terminal bile ducts, distinguished by the fact that they are very short, are called Herring's canals. Lined with a small number of flat cells. Herring channels become visible only at the level of the limiting plate.
These terminal bile ducts already exit into full-fledged bile ducts, which, passing through the portal canal, flow into the interlobular bile duct. In the anatomical atlas, they are visible on the dissected liver plate as small holes.
The lymphatic and nervous system of the portal canal
Initial lymphocapillaries start blindly inside the portal canal. Then they, already separated from the restrictive plate by a narrow slit called Malle's space, form into lymphatic vessels. It should be noted that there are no interlobular among them.
Nerve fibers of the adrenergic type are accompanied by blood vessels, innervating the portal canal itself. Then, passing into the hepatic lobule, an intralobular web is formed inside it. Cholinergic nerve fiberstypes are also included in the slice.
Slice functions
The functions of the hepatic lobule are the functions of the entire liver, since it is a constituent segment of this large gland. The range of tasks of the body, 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, metabolism of mineral elements.
- Participation in pigment metabolism. It manifests itself in the capture of bilirubin and its excretion along with bile.
- Carbohydrate metabolism. Participation in the process involves the formation and subsequent oxidation of glucose, as well as the synthesis and breakdown 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 necessary for the life of the whole organism - coagulation factors, albumins, etc.
- The most important is the cleansing, detoxifying function. It is the liver - the main organ that cleanses the entire body of toxins. Through the portal vein, harmful, foreign substances, metabolic products enter the segments of the liver from the gastrointestinal tract. In this organ, they are further neutralized, after which they are excreted from the body.
The hepatic lobule is a component of the body of the liver. The organ has a complex structure. The capillaries, lymphatic vessels, bile ducts and nerves supplying the segment pass through its portal canals.endings. The basis of the lobule is special liver cells - hepatocytes, which have their own unique structure. The functions of both the entire liver and its lobules are similar.
