Shares, sectors and segments of the liver
W (CII) IV (CIV)
V (CV), VIII (CVIII)
VI (CVI), VII (CVII)
The left dorsal sector corresponding to the first (CI) hepatic segment includes the caudate lobe and is visible only on the visceral surface and the posterior part of the liver.
The left lateral sector (segment II-CII) encompasses the posterior region of the left lobe of the liver.
The left paramedian sector occupies the anterior part of the left lobe of the liver (III segment - CIII) and its square segment (IV segment - CIV) with a parenchyma on the diaphragmatic surface of the organ in the form of a band narrowing posteriorly (to the groove of the inferior vena cava).
The right paramedian sector is the hepatic parenchyma bordering the left lobe of the liver. This segment includes the V segment (CV) occupying the posterior medial part of the right lobe of the liver on its diaphragm surface.
The right lateral sector corresponding to the most lateral part of the right lobe of the liver includes VI-CVI (lies in front) and VII-CVII segments. The latter is located behind the previous one and occupies the posterolateral part of the diaphragmatic surface of the right lobe of the liver.
From the fibrous capsule deep into the liver are the layers of connective tissue that separate the parenchyma from the lobules, which are the structural and functional units of the liver.
The lobe of the liver (lobulus hepatis) has a prismatic shape, its diameter is 1.0-1.5 mm. The total number of lobes is approximately 500 thousand. The lobule is constructed from the radial convergent from the periphery to the center of the cell rows - the hepatic beams. Each beam consists of two rows of hepatic cells - hepatocytes. Between the two rows of cells within the hepatic canal are the initial sections of the biliary tract (bile duct, ductulus bilifer). Between the beams, the blood capillaries (sinusoids), which converge from the periphery of the lobule to its central vein (v.centralis), situated in the center of the lobule, are located radially. Between the sinusoidal capillary wall and hepatocytes there is a perisinusoidal space (Diss). Between the lobules there is a small amount of connective tissue, in the thickness of which there are interlobular bile ducts, arteries and veins. Interlobular protochek, artery and vein are next, forming the so-called hepatic triad. Thanks to this design, hepatocytes are secreted in two directions: bile ducts - bile, blood glucose, urea, fats, vitamins, etc., entered the liver cells from the bloodstream or formed in these cells.
Hepatocytes have a polygonal shape, their diameter is 20-25 microns. Most hepatocytes have one nucleus, a smaller part - two or more nuclei. The cytoplasm of the hepatocyte appears large or fine-mesh depending on the severity and composition of the inclusions (lipids, pigments). Hepatocytes have many mitochondria, expressed endoplasmic reticulum and Golgi complex, a significant number of ribosomes, lysosomes, as well as microfiber with products of fatty acid metabolism. In the cytoplasm many grains of glycogen. The cytolemma of hepatocytes has numerous microvilli, facing the perisinusoidal space, towards the blood capillaries.
From the intrahepatic lobes the biliary tract originates.
In the liver lobes there are bile ducts, or tubules. The clearance (diameter) of bile ducts is 0.5-1 μm. They do not have their own walls, since they are enlarged zones of intercellular spaces between the rows of hepatocytes that make up the hepatic girder. The bile ducts have short blind branches (intermediate tubules of Goering), which enter between adjacent hepatocytes forming the walls of the bile ducts. The bile ducts (tubules) start blindly near the central vein and go to the periphery of the lobule, where the bile ducts (ductuli interlobulares) open into interlobular (around the lobular). Interlobular grooves connect to each other, increase in diameter, form the right and left hepatic ducts (ductus hepaticus dexter et sinister). In the gates of the liver, these two ducts are connected to a common hepatic duct 4-6 cm long. Between the sheets of the hepatic-duodenal ligament the common hepatic duct connects to the vesicular duct (duct of the gallbladder) and forms a common bile duct.
The common bile duct (ductus choledochus, s.biliaris) is located between the sheets of the hepatic-duodenum ligament, anterior to the portal vein and to the right of the hepatic artery. Then the common bile duct goes behind the upper part of the duodenum, then between its descending part and the head of the pancreas. In the wall of the duodenum, the common bile duct connects to the duct of the pancreas and together with it forms an expansion - the hepatic-pancreatic ampulla (ampulla hepatopancreatica). The ampulla opens into the duodenum on the top of its large papilla. In the walls of the mouth of the hepatic pancreatic ampulla there is a thickening of the circular bundles of myocytes forming the sphincter of the hepatic pancreatic ampulla, or the sphincter of Oddi. The distribution of circular smooth muscle bundles of this sphincter is uneven. Smooth muscle bundles are most concentrated at the base of the large papilla and have a thickness of up to 75 μm, in the thickness of the nipple - 40 μm. The length of the sphincter is 15-20 microns.
In the period between digestion processes, the sphincter of Oddi is closed, the bile accumulates in the gallbladder, where it is concentrated. During the digestive process, the sphincter of Oddi is opened and the bile enters the duodenum
In the walls of the terminal part of the common bile duct, before its fusion with the duct of the pancreas, there is also a sphincter. This sphincter of the common bile duct, with its contraction, blocks the flow of bile from the biliary tract into the hepatic pancreatic ampulla and further into the duodenum.
The walls of interlobular bile ducts are formed by a single-layered cubic epithelium. The walls of the hepatic, vesical and common bile duct have three membranes. The mucous membrane is lined with a single-layered high prismatic epithelium. In the epithelium there are also goblet cells. The propria of the mucous membrane is well developed, contains many longitudinal and circular elastic fibers, a few multicellular mucous glands. The submucosa is poorly developed. The muscular membrane is thin, consisting mainly of spiral beams of smooth myocytes, between which there is connective tissue.
Innervation of the liver
The liver is innervated by the branches of the vagus nerves and by the hepatic (sympathetic) plexus.
Blood supply to the liver
The hepatic artery and the portal vein enter the gates of the liver. The artery carries arterial blood, the portal vein - venous blood from the stomach, pancreas, intestine, spleen. Inside the liver, the artery and portal vein branches to the interlobular arteries and interlobular veins, which are located along with the biliary interlobular ducts between the lobules of the liver. From the interlobular veins in the lobules extend the wide blood capillaries (sinusoids) that flow into the central vein. In the initial sections of the sinusoid arterial capillaries flowing from the interlobular arteries. The central veins of the hepatic lobules are connected to each other, forming subdural (collective) veins. Sublobular veins merge with each other, become larger and eventually form 2-3 hepatic veins. They come out of the liver in the region of the furrow of the inferior vena cava and flow into this vein.
Outflow of lymph: in the hepatic, celiac, right lumbar, upper diaphragmatic, perigrudinous lymph nodes.
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Age features of the liver
The newborn has a large liver and occupies more than half the volume of the abdominal cavity. The weight of the liver in a newborn is 135 g, which is 4.0-4.5% of the body weight (in adults 2-3%). The diaphragmatic surface of the liver is convex, the left lobe of the liver is equal in size to the right or larger than it. The lower edge of the liver is convex, under its left lobe is the colon. The upper border of the liver on the right sredneklyuchichnoy line is at the level of V rib, and on the left - at the level of the VI rib. The left lobe of the liver crosses the costal arch along the left sredneklyuchichnoy line. The transverse size of the liver in a newborn is 11 cm, longitudinal - 7 cm, vertical - 8 cm. In a child 3-4 months the intersection of the costal arch with the left lobe of the liver due to a decrease in its size is already on the pericarp line. In newborns, the lower edge of the liver on the right sredneklyuchichnoy line protrudes from beneath the costal arch by 2.5-4.0 cm, and along the anterior median line - by 3.5-4.0 cm below the xiphoid process.
Sometimes the lower edge of the liver reaches the right ilium bone. In children 3-7 years, the lower edge of the liver is below the costal arch by 1.5-2.0 cm (along the middle clavicular line). At the child of 7 years the weight of a liver reaches 700. After 7 years the bottom edge of a liver from under a costal arch does not leave; under the liver is only the stomach. From this time on, the skeletonopia of the child's liver is almost the same as that of an adult human skeleton. In children, the liver is very mobile, and its position easily changes when the position of the body changes. The final size of the liver reaches after 20-29 years. After 60-70 years the weight of the liver decreases, its connective tissue grows. In the hepatocytes with age, the amount of lipofuscin increases, the number of dividing hepatocytes decreases sharply, the sizes of their nuclei increase.
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