Liver

The liver (hepar) is the largest gland, has a soft consistency, reddish-brown color. The length of the liver in an adult is 20-30 cm, width - 10-21 cm, the height varies from 7 to 15 cm. The weight of the liver is 1400-1800 g. The liver participates in the metabolism of proteins, carbohydrates, fats, vitamins; performs protective, disinfecting and other functions. In the uterine period, the liver is also a hematopoietic organ.

The liver distinguishes diaphragmatic and visceral surfaces. The diaphragmatic surface (fdcies diaphragmatica) is convex, directed upward and anteriorly. The visceral surface (facies visceralis) is flattened, directed downwards and posteriorly, its relief is uneven due to the internal organs adjacent to the liver.

Front, right and left, both liver surfaces converge.

The lower (anterior) margin of the liver (margo inferior) is acute, the posterior margin of the liver is rounded.

The liver is located in the right hypochondrium (predominantly) and in the region of the epigastrium. On the bone of the skeleton (on the ribs and vertebral column), the liver is projected so that to the right and front of the middle clavic line the highest point of the liver (right lobe) is determined at the level of the fifth intercostal space. The lower edge of the liver on the right under the axillary line is determined at the level of the tenth intercostal space. Further, the lower boundary passes forward along the right costal arch. At the level of the right middle clavicle line, the lower border of the liver is at the level of the costal arch, then goes from right to left and upward, crossing the epigastrium. At level VI of the left costal cartilage the lower border (the left share of the liver) crosses the costal arch and to the left of the sternum connects to the upper border of the liver. Behind and to the right (along the scapular line) the border of the liver is at the level between the seventh intercostal space at the top and the upper edge of the XI rib from below.

At the top, the diaphragm surface is to the right and partially to the left dome of the diaphragm. In front, the liver in the upper part adjoins the costal part of the diaphragm and below it to the anterior abdominal wall. Behind the liver is to the X-XI thoracic vertebrae, to the diaphragm's legs, the abdominal esophagus, the aorta, the right adrenal. From below, the liver touches the cardiac part, the body and the pyloric part of the stomach, the upper part of the duodenum, the right kidney and the right adrenal, right bend and right side of the transverse colon.

The surface of the liver is smooth, shiny, covered with a peritoneum, with the exception of a small area on its posterior surface. The peritoneum, passing from the diaphragm to the liver, forms the so-called ligaments. The crescent ligament (lig.falciforme) of the liver, located in the sagittal plane, extends from the diaphragm and the anterior abdominal wall to the diaphragmatic surface of the liver. In the frontal plane there is a coronary ligament (lig.coronarium), which connects with the posterior edge of the crescent ligament. On the sides, the coronary ligament forms extensions known as the right and left triangular ligament of the liver (lig.triangulare dextrum et lig.triangulare sinistrum). In the lower free edge of the crescent ligament there is a round ligament of the liver (lig.teres hepatis), which looks like a dense strand. It is a overgrown umbilical vein that connects the navel to the portal of the liver. From the gate of the liver to the small curvature of the stomach and to the initial part of the duodenum, two leaves of the peritoneum are directed, forming the (left) hepatic-gastric ligament (lig.hepatogastricum) and (on the right) hepatic-duodenal ligament (lig.hepatoduodenale).

On the diaphragmatic surface of the left lobe there is a cardiac depression - a trace of adherence to the liver of the heart (through the diaphragm).

Anatomically, the liver secrete two large lobes: the right and left (lobus hepatis dexter and lobus hepatis sinister). The border between the larger right and the smaller left lobes of the liver on its diaphragm surface is the sickle ligament of the liver. On the visceral surface, the border between these lobes is the frontal groove of the circular ligament of the liver, and behind it there is a gap of the venous ligament, in which there is a venous ligament, which is an overgrown venous duct that connected the umbilical vein to the inferior vena cava with the fetus.

On the visceral surface of the liver, to the right of the groove of the circular ligament and the slit of the venous ligament, there is a right sagittal groove. Ahead this furrow widens and forms a pit of the gallbladder (fossa vesicae biliaris, s.felleae), and posteriorly forms a furrow of the inferior vena cavae (sulcus venae cavae). Between the right and left sagittal grooves is a deep transverse furrow, called the gates of the liver. The portal of the liver (porta hepatis) is at the level of the posterior edge of the pit of the gallbladder and the slit of the circular ligament. The portal of the liver includes the portal vein, its own hepatic artery, nerves; come out a common hepatic duct (sometimes right and left liver) and lymphatic vessels.

On the visceral surface of the liver, within its right lobe, two small areas are distinguished: a square and a caudate lobe. The square fraction (lobus quadratus) is bounded on the left by the slit of the circular ligament, to the right - by the pit of the gallbladder, at the back - by the gates of the liver. The tails (lobus caudatus) are located between the neck of the venous ligament on the left, the furrow of the inferior vena cava on the right and the portal gates in front. The hvostataya share has two processes. The tail process (processus caudatus) is located between the gates of the liver and the furrow of the inferior vena cava. The cococephalic processus (processus papillaris) is also directed anteriorly, it rests against the gates of the liver next to the ligament of the venous ligament.

On the visceral surface of the liver, there are impressions from contact with internal organs. On the visceral left surface there is a gastric impression (impressio gastrica). The posterior part of the left lobe has an esophageal impression (impressio oesophagea). On the square lobe and on the site adjacent to the pit of the gallbladder, there is an impression of the duodenum (impressio duodenalis). To the right of it, on the right lobe, the renal impression (impressio renalis) is distinguished. To the left of the renal depression, next to the groove of the inferior vena cava, is the adrenal depression (impressio suprarenalis). On the visceral surface along the lower edge of the liver, the colon-intestinal impression (impressio colica) is oriented.

In the liver, 5 sectors and 8 segments are isolated. The sector is understood as the liver site, which is supplied by the branch of the portal vein of the second order and the branch of its own hepatic artery, also of the second order. A sectoral bile duct emerges from the sector. The segment of the liver is a region of the liver corresponding to the branch of the portal vein of the third order, from which the segmentary bile duct emerges. The numbering of segments on the visceral surface is made in the direction from the groove of the inferior vena cava in a clockwise direction. In the left lobe there are 1-4 segments, in the right segment there are 5-8 segments.

[1], [2],

Shares, sectors and segments of the liver

Share of	Sector	Segment
Left share	Left dorsal	I (CI)
	Left lateral	II (CII)
	Left paramedian	W (CII) IV (CIV)
Right share	Right paramedian	V (CV), VIII (CVIII)
	Right lateral	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.

[3], [4], [5], [6], [7],

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.

[8], [9], [10], [11], [12], [13], [14], [15]