Development: from the endoderm, at the end of 3 weeks. Embryogenesis protrusion lane. walls of the trunk intestine (hepatic bay), growing into the mesentery. Then it is divided into cranial (the upper part of it develops the liver and hepatic duct) and caudal (the lower gallbladder and bile duct from it) the mouth of the oven bay closes the common bile duct. Epithelial cells grow into the mesentery and encircle the strands, between them there is a network of blood capillaries (the beginning of the portal vein from the yolk vein). The connective tissue grows, dividing the liver into lobules.
Functions: neutralization of metabolites, inactivation of hormones, bioganic amines, drugs; protection from microbes and alien things; synthesis of glycogen, blood plasma proteins (albumin, fibrinogen), bile; accumulation of fat-soluble vitamins; in the embryonic period, the hematopoietic organ.
Regeneration: by a compensatory increase in cell size (hypertrophy) and the reproduction of hepatocytes, a high ability to physiological and reparative regulation. Age change: an increase in lipofuscin pigment, hypertrophy and polyploidy of the nuclei, proliferation of connective tissue between the lobules.
Structure: It is covered with a connective tissue capsule, the cat fuses with the peritoneum, the parenchyma sucks from the hepatic lobules. Liver lobule (classic): structural-functional unit. liver shape 6-faced prism with a convex nar-th on top and vnutr. flat. The interlobular connective tissue forms a stroma, in which there are no blood vessels and bile ducts. The lobule consists of hepatic beams (radially directed double rows of hepatocytes) and between them intralobular sinusoidal blood capillaries (from pyrephia to the center). Intralobular capillaries consist of squamous endotheliocytes between them, porositic areas, as well as stellate macrophages (Kupffer cells) are of monocytic origin and process form. From the lumen adjoin the cells pit-cl(pitted) - refer to granular lymphocytes have secretory granules. F-tions - stimulate the division of hepatocytes, phagocytize dead cells. The base membrane is absent. Capillaries surrounds the perisinusoidal space. It contains reticular waves, liquid (for blood filtration by hepatocytes) and perisinusoidal lipocytes (between heptocytes, 5-10 microns. Sod-t fat drops store fat-soluble vitamins, are capable of fiber formation). Furnace night beams-from hepatocytes, connected by desmosomes like a lock. They secrete glucose, blood proteins, bile. M / y hepat-mi inside the beam- bile capillaries(tubules). Their wall is hepatitis connected by desmosomes with microvilli. Zh-e cann-tsy flow into cholangiols-tubules from 2-3 cells. Cholangiols flow into the interstitial bile ducts. Hepatitis on one side (vascular) is directed to the sinus cap, the other (biliary) to the bile canaliculi (excretion of bile). The modern liver consists of segments of the liver plates, inside there are blood lacunae with a perilacunary space.
Hepatocytes polygonal f-ma 20-25 microns. The nuclei are rounded 7-16 microns. Polyploid. Cytoplasm: grEPS (synthesis of blood proteins), agrEPS (metabolism of carbohydrates), EPS ob-et microsomes (neutralize toxins), peroxisomes (metabolism of fat-x to-t), mits round, oval-e, filamentous-e, lysosomes , Ap-t Golgi in biliary pov-ti (secretion of bile). On the vascular and biliary surface of the microvilli.
Portal hepatic lobule includes segments of 3 adjacent hepatic lobules surrounding the triad. Therefore, it is triangular in shape, in its center lies a triad, and on the periphery of the central veins. In this regard, in the portal lobule, the blood flow through the blood capillaries is directed from the center to the periphery. (Scheme 1)
Hepatic acinus formed by segments of 2 adjacent hepatic lobules, therefore, has the shape of a rhombus. At its acute angles, the central veins pass, and at the obtuse angle, the triad, from which its branches (around the lobules) go inside the acinus. From these branches, hemocapillaries are sent to the veins. In the acinus, as well as in the portal lobule, the blood supply is carried out from its central sections to the peripheral ones. (Scheme 2)
(1) portal lobule 
(2) hepatic acinus
BLOOD SUPPLY. Consists of 3 parts: a) the system of blood flow to the lobules; b) the blood circulation system inside them; c) the system of outflow of blood from the lobules.
A) Presented by the portal vein- collecting blood from all unpaired organs of the abdominal cavity, rich in substances absorbed in the intestine, delivers it to the liver. hepatic artery- bringing blood from the aorta, saturated with oxygen. (Lobar, segmental, interlobular veins and arteries.) Together: artery, vein and bile duct form a triad.
b) from around the lobular veins and arteries blood capillaries begin. They enter the hepatic lobules and merge to form intralobular sinusoidal vessels, which make up the blood circulation system in the hepatic lobules. Flows through them mixed blood in the direction from the liver to the center of the lobules.
V) Central veins the system of outflow of blood from the lobules begins. Upon exiting the lobules, these veins drain into the collecting veins, or sublobular veins passing in the interlobular septa. They Not are part of the triad. They merge and form branches of the hepatic veins, which in the amount of 3-4 exit the liver and flow into into the inferior vena cava.
Bile ducts: 1)intrahepatic- bile tubules, cholangiols, interlobular bile ducts (included in the triads, one-line cube) 2) extrahepatic- right and left → common hepatic ducts → cystic → common bile duct. Mucus ob-ka one-layer highly prismatic epithelium, goblet-shaped cells, own plas-ka from elastic fibers and mucous glands. Mouse-I ob-ka - circular bundles of smooth myocytes. Adventic - loose connective tissue.
Gallbladder. There are three shells in the wall: mucous, muscular and external - serous (adventitia)
The mucosa has two layers: integumentary epithelial (single-layer prismatic border) and own plate with simple branched alveolar-tubular mucous glands in the neck of the gallbladder. Border epithelial cells contain microvilli, secret. granules; basal cells are single hormone-producing diffuse endocrine cells. systems.
Muscular membrane has circularly and longitudinally oriented smooth myocytes, many elastic fibers in the endomysium and perimysium. In the region of the neck, it forms a sphincter.
adventitial sheath consists of a dense fibrous Comm. tissue (from the side of the liver), the serous membrane is lined with mesothelium.
PANCREAS.
Development. At 3-4 weeks from 2 rudiments: 1) epithelium - from the dorsal and ventral protrusions of the endodermal intestine; 2) connected tissue stroma, blood vessels, capsule - from mesenchyme; At the 3rd month, differentiation into endo- and exocrine parts takes place;
Structure. Covered with woven capsule; has 2 parts (endo/exocrine).
exocrine part. The exocrine part is organized like a complex alveolar-tubular gland, consists of acini (adenomers) 100-150 microns in size, intercalary, intralobular, interlobular and common excretory ducts. Produces pancreatic juice rich in digestive enzymes.
Pancreatic acinus comp. from acinocytes and centroacinous epithelial cells.
Acinocytes: have the shape of pyramids; lie on the basal membrane; are interconnected by desmosomes and endplates; have granules of an immature zymogen enzyme; Functions: synthesis of food farm proteins (trypsin, lipase, amylase).
duct insert- maybe nah-Xia in the center and on the side of the end section. Centroacinous epithelial cells are poor in organelles and have microvilli. Interacinous duct covered with cuboidal epithelium; class. have many mitochondria and are connected by desmosomes; The interacinous duct flows into the intralobular duct, which is lined with cuboidal epithelium, has main EPS, ribosomes, MH, KG. intralobular.duct flows into the interlobular duct-lined with connective tissue and carries a secret into common duct-covered with prismatic epithelium, contains goblet exocrinocytes and endocrinocytes producing cholecystokein and pancreazimin.
DRAW: Acinus and intercalary duct of the pancreas: AC - acinocytes, ZG - zymogenic granules, MSC - intercellular secretory tubules, CAC - centroacinous cells.
endocrine part. The endocrine part is represented by pancreatic islets of Langerhans 100–200 µm in size, uniting several hundred endocrine cells of insulocytes, blood capillaries (fenestrated type), nerve fibers and connective tissue elements (with a predominance of reticular fibers).
Insulocytes- small light endocrine cells with a rounded nucleus, nucleolus, granular endoplasmic reticulum, Golgi complex, mitochondria and granular secretory vesicles containing peptide hormones. There are 5 main types of insulocytes: A-, B-, D-, D₁- and PP-cells
Sometimes found EC cells that produce the biogenic amine serotonin, and G cells that secrete gastrin.
A-cells(acidophiles) make up 20-25% of the total number of insulocytes, are located on the periphery of the islets, have an oval shape, secretory granules are stained with acidic dyes, with a narrow light halo and an electron-dense core containing the hormone glucagon, which stimulates glycogenolysis, lipolysis and an increase in glucose levels in blood.
B cells(basophils) make up 60-70%, are located in the center of the islets, have an oval shape, secretory granules stain basophilically, with a wide light halo and an electron-dense core, contain zinc and the hormone insulin, which stimulates the uptake of glucose by cells of various tissues.
D cells(dendritic) make up 5-10%, are located on the periphery of the islets, have a radiant polygonal shape, large secretory granules of moderate electron density containing the hormone somatostatin, which inhibits the activity of acinocytes, A- and B-cells of the islets.
D₁ cells differ from type D endocrinocytes in having smaller secretory granules. They produce VIP, which stimulates the exocrine activity of the pancreas.
PP cells(pancreatic polypeptide is produced) make up 2-5%, are located on the periphery of the islets, contain small polymorphic secretory granules with a homogeneous matrix of various electron densities. Inhibit the activity of acinocytes.
Apart from exocrine(acinic) and endocrine(insular) cells, another type of secretory cells has been described in pancreatic lobules - intermediate, or acinoislands, cells. They have granules of two types - large zymogenic inherent in acinous cells, and small, typical for insular cells (A, B, B, PP).
12. Classification of GEP of endocrine cells, features of their structure and functioning. Gastroenteropancreatic system (GEPS).
The endocrine system is the largest link in the diffuse endocrine system. Difference >20 cell types. They are located endoepithelially, they are conical in shape with a wide base and a narrow apex part. The biologically active substances they secrete - neurotransmitters and hormones - appear to be local (regulating the function of the glands and the main muscles of the vessels) and the general effect on the org. The number of organelles and secretory granules died in the cells, differing in the shape, size and structure of the dense core. Cl section into 2 types: 1) open reached the apex of epit and im microvile receptors, capturing changes in the chemical composition of food 2) closed type did not reach the apex of the epithelium. Appeared on the 6th week of embryogenesis.
DRAW: Cells of the diffuse endocrine system 1 – cells of open (COT) and closed (CST) types, 2 – ultrastructure of a single hormone-producing cell, CAP – capillary, NV – nerve fiber, SP – synaptic vesicles, SG – secretory granules.
GEPS. EC cells- cardial zh-zy food-yes, zh-zy stomach, epit mucus obol intestines, podzhel zh-za; secret serotonin during the day (regulated suction of water and electrolytes, strengthened the intake of org digester tubes), melatonin at night (regulated photoperiodicity functions, antiox, antistressor, inhibition of apoptosis, secretion of HCl, slowing down aging), substance P(modulation of painful feelings, increased motility kish, salivary secretion, secret yellow yellow). G cells-pyloric gastric glands, epithelium mucus obol duodenum and jejunum; secret gastrin (increased secretion of HCl, pepsinogen, motor yellow, intestinal, gallbladder, secret act of yellow glands, enkephalin (anesthetic, feeling satiety, increased release gastrin, brake secret pancre farm-v). A-cells- own gastric glands, islands of stomach glands; secret glucagon (increased intraclear breakdown of glycogen in TC, increased soda glitch in the blood, torm secretion of stomach glands, burns of glands, motor yellow and kish), cholecystokinin and pancreozymin (strength secret farms podzhel zh-zoy, pepsinogen in zhel, motor kish, bilious belly, brake secr HCl and motor zhel), enkephalin. S cells-duod zh-zy, epit mucus obol kish; secret secretin (increased sec HCO3- podzhel zh-zoy, potency action of holocystokin, pancreozyme on it, stim reduces activity of kish, brake secret HCl, motor yellow). K cells- epithelium mucosa obol thin kish; secret gastroinhibiting peptide (torm release of gastrin, increased secretion in kish, release of insulin). L cells- Epit slihz obol colonic; secret enteroglucagon (hepatic glucogenolysis). I cells- epithelium mucosa obol thin kish; secretion of cholecystokinin and pancreozymin. D cells-Islands waited for zh-zy, zh-zy zhel, epit mucus obol kish; secret somatostatin (torm release hormone cells GEP-syst, secret esophagus zh-z, motor yellow and bile bellies). M cells- crypts of small intestine; secretion of motilin (stimulation of synthesis and secretion of pepsinogen, motor of yellow and small intestine, duodenal secretion). D₁ cells-localization as D-cl;secr VIP-vasoact intestinal pept (relaxed hl vascular miots, gall bladder, yellow, torm secret in yellow, strengthened secret in kish, enriching pancreatic juice HCO3-). P-cells- zhel zhel, zhel zhel, epit mucus obol kish; secret bombesin (stim releases gastrin, cholecystokin, pancreozyme, enteroglucogon, neurotensin, pancreatic polypept). ECL cells-own w-zy yellow; secret histamine (increased activity of Panetov cells and HCl). PP cells-pyloric zh-zy yellow, podzhel zh-za, epit mucus obol kish; secret pancreatic polypeptide (antag pancreozyme, cholecysts, motilin, enhanced prolif cl of the pancreas, liver, epithelium mucosa of the small intestine). B cells- islands podzhel w-zy; secret insulin (hypoglycemic effect). IG cells- epithelium mucus obol 12 duodenum and jejunum; secret gastrin (see G-cl). TG cells-tonk quiche; secret gastrin, cholecystokinin. N-cells-epitis mucus obol ileum kish; neurotensin secretion (stimulating the gastrointestinal tract, releasing glucagon, inhibiting the release of insulin and HCl). YY cells-epith mucus about podvzd, rim and straight kish; secret YY-polypeptide (regular secret act goblet cl).
The liver is the largest organ in humans. Its mass is 1200-1500 g, which is one fiftieth of the body weight. In early childhood, the relative mass of the liver is even greater and at the time of birth is equal to one sixteenth of the body weight, mainly due to the large left lobe.
The liver is located in the right upper quadrant of the abdomen and is covered by the ribs. Its upper border is approximately at the level of the nipples. Anatomically, the liver is divided into two lobes - right and left. The right lobe is almost 6 times larger than the left (Fig. 1-1-1-3); It has two small segments: caudate lobe on the back and square share on the bottom surface. The right and left lobes are separated in front by a fold of the peritoneum, the so-called falciform ligament, behind - by a groove in which the venous ligament passes, and from below - by a groove in which the round ligament is located.
The liver is supplied with blood from two sources: portal vein carries venous blood from the intestines and spleen, and hepatic artery, departing from the celiac trunk, provides the flow of arterial blood. These vessels enter the liver through a depression called gates of the liver which is located on the lower surface of the right lobe closer to its posterior edge. At the hilum of the liver, the portal vein and hepatic artery give branches to the right and left lobes, and the right and left bile ducts join to form the common bile duct. hepatic nerve plexus contains fibers of the seventh-tenth thoracic sympathetic ganglia, which are interrupted in the synapses of the celiac plexus, as well as fibers of the right and left vagus and right phrenic nerves. It accompanies the hepatic artery and bile ducts to their smallest branches, reaching the portal tracts and the liver parenchyma.
Rice. 1-1. Liver, front view. 765.
Rice. 1-2. Liver, rear view. See also color illustration on p. 765.
Rice. 1-3. Liver, bottom view. See also color illustration on p. 765.
venous ligament, a thin remnant of the fetal ductus venosus, departs from the left branch of the portal vein and merges with the inferior vena cava at the confluence of the left hepatic vein. round bundle, a rudiment of the umbilical vein of the fetus, runs along the free edge of the falciform ligament from the navel to the lower edge of the liver and connects to the left branch of the portal vein. Small veins pass next to it, connecting the portal vein with the veins of the umbilical region. The latter become visible when intrahepatic obstruction of the portal venous system develops.
Venous blood flows from the liver to the right and left hepatic veins, which depart from the posterior surface of the liver and flow into the inferior vena cava near the place of its confluence with the right atrium.
Lymphatic vessels terminate in small groups of lymph nodes surrounding the gates of the liver. The efferent lymphatic vessels enter the nodes located around the celiac trunk. Part of the superficial lymphatic vessels of the liver, located in the falciform ligament, perforates the diaphragm and ends in the lymph nodes of the mediastinum. Another part of these vessels accompanies the inferior vena cava and ends in a few lymph nodes around its thoracic region.
inferior vena cava forms a deep furrow to the right of the caudate lobe, about 2 cm to the right of the midline.
gallbladder located in the fossa, which stretches from the lower edge of the liver to its gate.
Most of the liver is covered by the peritoneum, with the exception of three areas: the fossa of the gallbladder, the grooves of the inferior vena cava and part of the diaphragmatic surface located to the right of this groove.
The liver is held in its position due to the ligaments of the peritoneum and intra-abdominal pressure, which is created by the tension of the muscles of the abdominal wall.
Functional anatomy: sectors and segments
Based on the appearance of the liver, it can be assumed that the border between the right and left lobes of the liver runs along the falciform ligament. However, this division of the liver does not correspond to the blood supply or bile outflow tracts. At present, by studying the casts obtained by introducing vinyl into the vessels and bile ducts, it has been clarified functional anatomy liver. About on corresponds to the data received at research by means of methods of visualization.
The portal vein divides into right and left branches; each of them, in turn, is divided into two more branches that supply blood to certain areas of the liver (differently designated sectors). There are four such sectors. On the right are the anterior and posterior, on the left - the medial and lateral (Fig. 1-4). With this division, the border between the left and right sections of the liver does not run along the falciform ligament, but along an oblique line to the right of it, drawn from top to bottom from the inferior vena cava to the gallbladder bed. The zones of the portal and arterial blood supply of the right and left sections of the liver, as well as the bile outflow tracts of the right and left sides, do not overlap. These four sectors are separated by three planes that contain the three main branches of the hepatic vein.
Rice. 1-4. Sectors of the human liver. See also color illustration on p. 765.
Rice. 1-5. Scheme showing the functional anatomy of the liver. The three main hepatic veins (dark blue) divide the liver into four sectors, each of which has a branch of the portal vein; branching of the hepatic and portal veins resembles intertwined fingers. See also color illustration on p. 766.
On closer examination, the sectors of the liver can be divided into segments (Fig. 1-5). The left medial sector corresponds to segment IV, in the right anterior sector there are segments V and VIII, in the right posterior sector - VI and VII, in the left lateral - segments II and III. There are no anastomoses between the large vessels of these segments, but they communicate at the level of the sinusoids. Segment I corresponds to the caudate lobe and is isolated from other segments because it is not supplied with blood directly from the main branches of the portal vein, and blood from it does not flow into any of the three hepatic veins.
The above functional anatomical classification allows for the correct interpretation of X-ray data and is important for the surgeon planning liver resection. The anatomy of the bloodstream of the liver is very variable, which is also confirmed by the data of spiral computed tomography (CT) and magnetic resonance reconstruction.
Anatomy of the biliary tract (Fig. 1-6)
Left and right come out of the liver hepatic ducts, merging at the gate common hepatic duct. As a result of its merger with cystic duct the common bile duct is formed.
common bile duct passes between the sheets of the lesser omentum anterior to the portal vein and to the right of the hepatic artery. Located posterior to the first section of the duodenum in a groove on the posterior surface of the head of the pancreas, it enters the second section of the duodenum. The duct obliquely crosses the posterior medial wall of the intestine and usually joins with the main pancreatic duct to form hepato-pancreatic ampulla (ampulla of Vater). The ampoule forms a protrusion of the mucous membrane directed into the intestinal lumen, - major papilla of the duodenum (Vate-swarm papilla). Approximately 12-15% of the examined common bile duct and pancreatic duct open into the lumen of the duodenum separately.
Rice. 1-6. Gallbladder and bile ducts. See also color illustration on p. 766.
The dimensions of the common bile duct, when determined by different methods, are not the same. The diameter of the duct, measured during operations, ranges from 0.5 to 1.5 cm. In endoscopic cholangiography, the diameter of the duct is usually less than 11 mm, and a diameter of more than 18 mm is considered pathological. In an ultrasound examination (ultrasound), it is normally even smaller and amounts to 2-7 mm; with a larger diameter, the common bile duct is considered dilated.
Part of the common bile duct, passing through the wall of the duodenum, is surrounded by a shaft of longitudinal and circular muscle fibers, which is called sphincter of Oddi.
gallbladder - pear-shaped bag 9 cm long, capable of holding about 50 ml of liquid. It is always located above the transverse colon, adjacent to the duodenal bulb, projecting onto the shadow of the right kidney, but at the same time being located significantly in front of it.
Any decrease in the concentration function of the gallbladder is accompanied by a decrease in its elasticity. Its widest section is the bottom, which is located in front; it is he who can be palpated in the study of the abdomen. The body of the gallbladder passes into a narrow neck, which continues into the cystic duct. Spiral folds of the mucous membrane of the cystic duct and the neck of the gallbladder are called Heister damper. Saccular dilation of the neck of the gallbladder, in which gallstones often form, is called Hartman pocket.
The wall of the gallbladder consists of a network of muscle and elastic fibers with indistinctly distinguished layers. The muscle fibers of the neck and bottom of the gallbladder are especially well developed. The mucous membrane forms numerous delicate folds; glands are absent in it, however, there are depressions penetrating into the muscle layer, called Luschka crypts. The mucosa does not have a submucosal layer and its own muscle fibers.
Sinuses of Rokitansky-Ashoff - branched invaginations of the mucous membrane, penetrating through the entire thickness of the muscular layer of the gallbladder. They play an important role in the development of acute cholecystitis and gangrene of the bladder wall.
Blood supply. The gallbladder is supplied with blood from cystic artery. This is a large, tortuous branch of the hepatic artery, which can have a different anatomical location. Smaller blood vessels exit the liver through the gallbladder fossa. Blood from the gallbladder through cystic vein flows into the portal vein.
The blood supply of the supraduodenal part of the bile duct is carried out mainly by the two arteries accompanying it. Blood in them comes from the gastroduodenal (bottom) and right hepatic (top) arteries, although their connection with other arteries is also possible. Strictures of the bile ducts after vascular damage can be explained by the peculiarities of the blood supply to the bile ducts.
Lymphatic system. In the mucous membrane of the gallbladder and under the peritoneum are numerous lymphatic vessels. They pass through the node at the neck of the gallbladder to the nodes located along the common bile duct, where they connect with the lymphatic vessels that drain lymph from the head of the pancreas.
Innervation. The gallbladder and bile ducts are abundantly innervated by parasympathetic and sympathetic fibers.
Development of the liver and bile ducts
The liver is laid in the form of a hollow protrusion of the endoderm of the anterior (duodenal) intestine at the 3rd week of intrauterine development. The protrusion is divided into two parts - hepatic and biliary. Hepatic part consists of bipotent progenitor cells, which then differentiate into hepatocytes and ductal cells, forming early primitive bile ducts - ductal plates. When cells differentiate, the type of cytokeratin in them changes. When the c-jun gene, which is part of the API gene activation complex, was removed in the experiment, liver development was stopped. Normally, fast-growing cells of the hepatic part of the protrusion of the endoderm perforate the adjacent mesodermal tissue (transverse septum) and meet with the capillary plexuses growing in its direction, coming from the vitelline and umbilical veins. Sinusoids are subsequently formed from these plexuses. Biliary part protrusions of the endoderm, connecting with the proliferating cells of the hepatic part and with the foregut, forms the gallbladder and extrahepatic bile ducts. Bile begins to be secreted around the 12th week. From the mesodermal transverse septum, hematopoietic cells, Kupffer cells and connective tissue cells are formed. In the fetus, the liver mainly performs the function of hematopoiesis, which fades in the last 2 months of intrauterine life, and by the time of delivery, only a small number of hematopoietic cells remain in the liver.
Anatomical abnormalities of the liver
Thanks to the widespread use of CT and ultrasound, there is more opportunity to detect anatomical abnormalities of the liver.
Additional shares. In pigs, dogs and camels, the liver is divided by connective tissue strands into separate lobes. Sometimes such an atavism is also observed in humans (the presence of up to 16 lobes is described). This anomaly is rare and has no clinical significance. The lobes are small and usually located below the surface of the liver so that they cannot be identified on clinical examination, but can be seen on a liver scan, surgery, or autopsy. Occasionally they are located in the chest cavity. The accessory lobe may have its own mesentery containing the hepatic artery, portal vein, bile duct, and hepatic vein. It can twist, requiring surgery.
Riedel's share| 35], which is quite common, looks like an outgrowth of the right lobe of the liver, shaped like a tongue. It is only a variant of the anatomical structure, and not a true accessory lobe. More common in women. Riedel's share is revealed as a mobile formation in the right half of the abdomen, which is displaced during inspiration along with the diaphragm. It can go down, reaching the right iliac region. It is easily confused with other masses in this area, especially with a lowered right kidney. Riedel's lobe is usually clinically silent and does not require treatment. The share of Riedel and other features of the anatomical structure can be detected by scanning the liver.
Cough grooves of the liver parallel depressions on the convex surface of the right lobe. Usually there are from one to six of them and they pass from front to back, deepening somewhat backwards. The formation of these grooves is thought to be associated with chronic coughing.
Liver corset- this is the name of the groove or stalk of fibrous tissue, passing along the anterior surface of both lobes of the liver immediately below the edge of the costal arch. The mechanism of stalk formation is unclear, but it is known to occur in older women who have worn a corset for many years. It looks like a formation in the abdominal cavity, located in front of and below the liver and does not differ in density from it. It may be mistaken for a liver tumor.
Share atrophy. Violation of the blood supply in the portal vein or the outflow of bile from the lobe of the liver can cause its atrophy. It is usually combined with hypertrophy of the lobes that do not have such disorders. Atrophy of the left lobe is often detected at autopsy or scanning and is probably associated with a decrease in blood supply through the left branch of the portal vein. The size of the lobe decreases, the capsule becomes thicker, fibrosis develops, and the pattern of vessels and bile ducts increases. Vascular pathology may be congenital.
The most common cause of atrophy of the lobes is currently obstruction of the right or left hepatic duct due to benign stricture or cholangiocarcinoma. Usually, this increases the level of alkaline phosphatase. The bile duct within the atrophic lobe may not be dilated. If cirrhosis has not developed, the elimination of obstruction leads to the reverse development of changes in the liver parenchyma. It is possible to distinguish atrophy in biliary pathology from atrophy as a result of impaired portal blood flow using 99m Te-labeled iminodiacetate (IDA) and colloid scintigraphy. The small size of the lobe with normal capture of IDA and colloid indicates a violation of portal blood flow as a cause of atrophy. The decrease or absence of capture of both isotopes is characteristic of the pathology of the biliary tract.
Agenesis of the right lobe. This rare lesion may be incidentally discovered during examination for a biliary tract disease and may be associated with other congenital anomalies. It can cause presinusoidal portal hypertension. Other segments of the liver undergo compensatory hypertrophy. It must be distinguished from lobar atrophy due to cirrhosis or cholangiocarcinoma, localized in the region of the liver gate.
Anatomical anomalies of the gallbladder and biliary tract described in chapter 30.
Borders of the liver (Fig. 1-7, 1-8)
Liver. The upper border of the right lobe runs at the level of the V rib to a point located 2 cm medially to the right midclavicular line (1 cm below the right nipple). The upper border of the left lobe runs along the upper edge of the VI rib to the point of intersection with the left midclavicular line (2 cm below the left nipple). At this point, the liver is separated from the apex of the heart only by the diaphragm.
The lower edge of the liver runs obliquely, rising from the cartilaginous end of the IX rib on the right to the cartilage of the VIII rib on the left. On the right midclavicular line, it is located below the edge of the costal arch by no more than 2 cm. The lower edge of the liver crosses the midline of the body approximately in the middle of the distance between the base of the xiphoid process and the navel, and the left lobe extends only 5 cm beyond the left edge of the sternum.
Rice. 1-7. borders of the liver.
Gallbladder. Usually its bottom is located at the outer edge of the right rectus abdominis muscle, at the point of its connection with the right costal arch (cartilage of the IX rib; Fig. 1-8). In obese people, it is difficult to find the right edge of the rectus abdominis muscle, and then the projection of the gallbladder is determined by the Gray Turner method. To do this, draw a line from the upper anterior iliac spine through the navel; the gallbladder is located at the point of its intersection with the right costal arch. When determining the projection of the gallbladder by this method, it is necessary to take into account the physique of the subject. The bottom of the gallbladder can sometimes be located below the iliac crest.
Examination methods
Liver. The lower edge of the liver should be palpated to the right of the rectus abdominis muscle. Otherwise, you can mistakenly take the upper lintel of the rectus sheath for the edge of the liver.
With a deep breath, the edge of the liver shifts 1-3 cm downwards, and normally it can be palpated. The edge of the liver can be sensitive, smooth or uneven, dense or soft, rounded or pointed. The lower edge of the liver can move down when the diaphragm is low, for example, with emphysema. The mobility of the edge of the liver is especially pronounced in athletes and singers. With some skill, patients can very effectively "shoot" the liver. A normal spleen can be palpated in the same way. With malignant neoplasms, polycystic or Hodgkin's disease, amyloidosis, congestive heart failure, severe fatty infiltration, the liver can be palpated below the navel. A rapid change in liver size is possible with successful treatment of congestive heart failure, resolution of cholestatic jaundice, correction of severe diabetes, or disappearance of fat from hepatocytes. The surface of the liver can be palpated in the epigastric region; while paying attention to any of its irregularities or soreness. An enlarged caudate lobe, such as in Budd-Chiari syndrome or in some cases of liver cirrhosis, may be palpated as a mass in the epigastric region.
Pulsation of the liver, usually associated with tricuspid valve insufficiency, can be palpated by placing one hand behind the lower right ribs and the other on the anterior abdominal wall.
Rice. 1-8. Projection of the gallbladder on the surface of the body. Method 1 - the gallbladder is located at the intersection of the outer edge of the right rectus abdominis muscle and the cartilage of the IX rib. Method 2 - a line drawn from the left superior anterior iliac spine through the navel crosses the edge of the costal arch in the projection of the gallbladder.
The upper border of the liver can be determined with relatively strong percussion from the level of the nipples downwards. The lower border is determined with weak percussion from the navel in the direction of the costal arch. Percussion allows determining the size of the liver and is the only clinical method for detecting small liver sizes.
The size of the liver is determined by measuring the vertical distance between the highest and lowest point of hepatic dullness during percussion along the midclavicular line. Usually it is 12-15 cm. The results of percussion determination of the size of the liver are as accurate as the results of ultrasound.
Rice. 1-9. The structure of the human liver is normal.
Rice. 1-10. The histological structure of the liver is normal. H - terminal hepatic vein; P - portal tract. Stained with hematoxylin and eosin, x60. See also color illustration on p. 767.
Rice. 1-11. The portal tract is normal. A - hepatic artery; G - bile duct. B - portal vein. Stained with hematoxylin and eosin. See also color illustration on With. 767.
Liver cells (hepatocytes) make up about 60% of the mass of the liver. They have a polygonal shape and a diameter of approximately 30 µm. These are single-nuclear, less often multi-nuclear cells that divide by mitosis. The life span of hepatocytes in experimental animals is about 150 days. The hepatocyte borders on the sinusoid and space of Disse, on the bile duct and adjacent hepatocytes. Hepatocytes do not have a basement membrane.
Sinusoids are lined with endothelial cells. Sinusoids include phagocytic cells of the reticuloendothelial system (Kupffer cells), stellate cells, also called fat-storing cells, Ito cells or lipocytes.
Each milligram of a normal human liver contains approximately 202 10 3 cells, of which 171 10 3 are parenchymal and 31 10 3 are littoral (sinusoidal, including Kupffer cells).
Disse space called the tissue space between hepatocytes and sinusoidal endothelial cells. In the perisinusoidal connective tissue pass lymphatic vessels, lined throughout with endothelium. Tissue fluid seeps through the endothelium into the lymphatic vessels.
Rice. 1-12. Functional acinus (according to Rappaport). Zone 1 adjoins the entrance (portal) system. Zone 3 is adjacent to the excretory (hepatic) system.
branches hepatic arteriole form a plexus around the bile ducts and flow into the sinusoidal network at its various levels. They supply blood to the structures located in the portal tracts. There are no direct anastomoses between the hepatic artery and the portal vein.
The excretory system of the liver begins with bile ducts(See fig. 13-2 and 13-3). They do not have walls, but are simply indentations on the contact surfaces of hepatocytes (see Fig. 13-1), which are covered with microvilli. The plasma membrane is permeated with microfilaments that form a supporting cytoskeleton (see Fig. 13-2). The surface of the tubules is separated from the rest of the intercellular surface by junctional complexes consisting of tight junctions, gap junctions, and desmosomes. The intralobular network of tubules drains into thin-walled terminal bile ducts or ductules (cholangiols, Hering's tubules) lined with cuboidal epithelium. They end in larger (interlobular) bile ducts located in the portal tracts. The latter are divided into small (less than 100 µm in diameter), medium (± 100 µm) and large (more than 100 µm).
Rice. 1-13. Blood supply of a simple liver acinus, zonal arrangement of cells and microcirculatory peripheral bed. Acinus occupies adjacent sectors of neighboring hexagonal fields. Zones 1, 2 and 3, respectively, represent areas supplied with blood with I, II and III degrees of oxygen and nutrients. In the center of these zones are the terminal branches of the afferent vessels, bile ducts, lymphatic vessels and nerves (PS), and the zones themselves extend to the triangular portal fields from which these branches emerge. Zone 3 is on the periphery of the microvasculature of the acinus, since its cells are as far away from the afferent vessels of its own acinus as they are from the vessels of the neighboring acinus. Perivenular the area is formed by the parts of zone 3 most distant from the portal triad of several adjacent acini. If these zones are damaged, the damaged area takes on the appearance of a starfish (the darkened area around the terminal hepatic venule located in its center - CPV). 1, 2, 3 - microcirculation zones; G, 2", 3" - zones of the neighboring acinus. See also color illustration on p. 768.
Electron microscopy and function of liver cells (Fig. 1-14, T-15)
The surface of hepatocytes is even, except for a few attachment sites (desmosomes). From them, uniformly spaced microvilli of the same size protrude into the lumen of the bile ducts. On the surface facing the sinusoid, there are microvilli of different lengths and diameters, penetrating into the perisinusoidal tissue space. The presence of microvilli indicates active secretion or absorption (mostly liquid).
Core contains deoxyribonucleoprotein. The human liver after puberty contains tetraploid nuclei, and at the age of 20 also contains octoploid nuclei. It is believed that increased polyploidy indicates a precancerous condition. One or two nucleoli are found in the chromatin network. The nucleus has a double contour and contains pores that provide exchange with the surrounding cytoplasm.
Mitochondria also have a double membrane, the inner layer of which forms folds, or cristae. Inside the mitochondria, a huge number of processes take place, in particular oxidative phosphorylation, during which energy is released. Mitochondria contain many enzymes, including those involved in the citric acid cycle and beta-oxidation of fatty acids. The energy released in these cycles is then stored in the form of ADP. Heme synthesis also takes place here.
Rough endoplasmic reticulum(SHES) looks like a row of plates on which ribosomes are located. Under light microscopy, they stain basophilically. They synthesize specific proteins, especially albumin, proteins of the blood coagulation system and enzymes. In this case, ribosomes can coil into a spiral, forming polysomes. G-6-Phase is synthesized in SES. Triglycerides are synthesized from free fatty acids, which are secreted in the form of lipoprotein complexes by exocytosis. SES may be involved in glucogenesis.
Rice. 1-14. Hepatocyte organelles.
Smooth endoplasmic reticulum(HES) forms tubules and vesicles. It contains microsomes and is the site of bilirubin conjugation, detoxification of many drugs and other toxic substances (P450 system). Steroids are synthesized here, including cholesterol and primary bile acids, which are conjugated with the amino acids glycine and taurine. Enzyme inducers, such as phenobarbital, increase the size of the HES.
Peroxisomes are located near hydroelectric power stations and glycogen granules. Their function is unknown.
Lysosomes - dense bodies adjacent to the bile ducts. They contain hydrolytic enzymes, upon release of which the cell is destroyed. They probably perform the function of intracellular purification from destroyed organelles, the life span of which has already expired. They deposit ferritin, lipofuscin, bile pigment and copper. Inside them, pinocytic vacuoles can be observed. Some dense bodies located near the tubules are called microbodies.
golgi apparatus consists of a system of cisterns and vesicles, which also lie near the tubules. It can be called a "storehouse of substances" intended for excretion into the bile. In general, this group of organelles - lysosomes, microbodies and the Golgi apparatus - ensures the sequestration of any substances that have been absorbed and must be removed, secreted or stored for metabolic processes in the cytoplasm. The Golgi apparatus, lysosomes, and tubules undergo particularly marked changes in cholestasis (see Chapter 13).
Rice. 1-15. Electron microscopic picture of a part of a normal hepatocyte. I am the core; Poison - nucleolus; M - mitochondria; W - rough endoplasmic reticulum; G - glycogen granules; mb - microvilli in the intracellular space; L - lysosomes; MP - intercellular space.
The cytoplasm contains glycogen granules, lipids and thin fibers.
cytoskeleton, supporting the shape of the hepatocyte, is composed of microtubules, microfilaments, and intermediate filaments. Microtubules contain tubulin and provide for the movement of organelles and vesicles, as well as the secretion of plasma proteins. Microfilaments are composed of actin, are capable of contraction and play an important role in ensuring the integrity and motility of the tubules, bile flow. Long branching filaments made up of cytokeratins are called intermediate filaments. They connect the plasma membrane to the perinuclear region and provide stability and spatial organization of hepatocytes.
The liver with duct system and the gallbladder develop from the hepatic diverticulum of the ventral endoderm of the primary midgut. The beginning of liver development is the 4th week of the prenatal period. The future bile ducts are formed from the proximal part of the diverticulum, and the hepatic beams are formed from the distal part.
Rapidly multiplying endodermal cells of the cranial part (pars hepatica) are introduced into the mesenchyme of the abdominal mesentery. Mesothermal sheets of the abdominal mesentery, as the hepatic diverticulum grows, form a connective tissue capsule of the liver with its mesothelial cover and interlobular connective tissue, as well as smooth muscles and the framework of the liver ducts. At the confluence of the ducts, the caudal part of the primary outgrowth expands (ductus cystica), forming the anlage of the gallbladder, which quickly elongates, taking the form of a sac. From the narrow proximal part of this branch of the diverticulum, the bladder duct develops, where many hepatic ducts open.
From the site of the primary diverticulum between the confluence of the hepatic ducts and the duodenum, the common bile duct (ductus choledochus) develops. The distal rapidly multiplying sections of the endoderm branch along the bile-mesenteric veins of early embryos, the spaces between the hepatic beams are filled with a labyrinth of wide and irregular capillaries - sinusoids, while the amount of connective tissue is small.
An extremely developed network of capillaries between strands of hepatic cells (beams) determines the structure of the developing liver. The distal parts of the branching hepatic cells turn into secretory sections, and the axial cords of the cells serve as the basis for a system of ducts through which the fluid flows out of this lobule towards the gallbladder. A double afferent blood supply to the liver develops, which is essential for understanding its physiological functions and clinical syndromes that occur when its blood supply is disturbed.
The process of intrauterine development of the liver is greatly influenced by the formation in a 4-6-week-old human embryo of a phylogenetically later than the yolk, allantoic circle of blood circulation.
Allantoic, or umbilical, veins, penetrating into the body of the embryo, are covered by the growing liver. There is an accretion of the passing umbilical veins and the vasculature of the liver, and placental blood begins to pass through it. That is why in the prenatal period the liver receives the most oxygenated and nutrient-rich blood.
After regression of the yolk sac, the paired yolk-mesenteric veins are connected to each other by bridges, and some parts become empty, which leads to the formation of the portal (unpaired) vein. The distal ducts begin to collect blood from the capillaries of the developing GI tract and direct it through the portal vein to the liver.
A feature of the blood circulation in the liver is that the blood, which has already once passed through the intestinal capillaries, is collected in the portal vein, again passes through the network of capillaries-sinusoids, and only then through the hepatic veins located proximal to those parts of the vitelline-mesenteric veins where the hepatic veins have grown into them. beams, goes directly to the heart.
So, there is a close interdependence and dependence between the glandular liver tissue and blood vessels. Along with the portal system, the arterial blood supply system is also developing, departing from the trunk of the celiac artery.
Both in an adult and in an embryo (and fetus), nutrients, after being absorbed from the intestine, first enter the liver.
The volume of blood in the portal and placental circulation is much greater than the volume of blood coming from the hepatic artery.
The mass of the liver depending on the period of development of the human fetus (according to V.G. Vlasova and K.A. Dret, 1970)
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Age, weeks |
Number of study |
Weight of raw liver, g |
The increase in liver mass is especially intense in the first half of human antenatal development. Fetal liver weight doubles or triples every 2-3 weeks. During 5-18 weeks of intrauterine development, the mass of the liver increases by 205 times, during the second half of this period (18-40 weeks) it increases only by 22 times.
In the embryonic period of development, the mass of the liver averages about 596 body weights. In the early periods (5-15 weeks), the mass of the liver is 5.1%, in the middle of fetal development (17-25 weeks) - 4.9, and in the second half (25-33 weeks) - 4.7%.
By birth, the liver becomes one of the largest organs. It occupies 1/3-1/2 of the volume of the abdominal cavity, and its mass is 4.4% of the body weight of the newborn. The left lobe of the liver is very massive at birth, which is explained by the peculiarities of its blood supply. By 18 months of postnatal development, the left lobe of the liver decreases. In newborns, the liver lobules are indistinctly demarcated. The fibrinous capsule is thin, there are delicate collagen and thin elastin fibers. In ontogenesis, the rate of increase in liver weight lags behind body weight. So, the mass of the liver doubles by 10-11 months (body weight triples), by 2-3 years it triples, by 7-8 years it increases by 5 times, by 16-17 years - by 10 times, by 20-30 years - in 13 times (body weight increases 20 times).
Liver weight (g) depending on age (no E. Boyd)
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boys | ||||
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newborns | ||||
The diaphragmatic surface of the liver of a newborn is convex, the left lobe of the liver is equal in size to the right one or exceeds it. The lower edge of the liver is convex, under its left lobe is the descending colon. The upper border of the liver along the right midclavicular line is at the level of the 5th rib, and along the left - at the level of the 6th rib. The left lobe of the liver crosses the costal arch along the left midclavicular line. In a child of 3-4 months, the place of intersection of the costal arch with the left lobe of the liver, due to a decrease in its size, is already on the peristernal line. In newborns, the lower edge of the liver along the right midclavicular line protrudes from under the costal arch by 2.5-4.0 cm, and along the anterior midline - 3.5-4.0 cm below the xiphoid process. Sometimes the lower edge of the liver reaches the wing of the right ilium. In children aged 3-7 years, the lower edge of the liver is 1.5-2.0 cm below the costal arch (along the midclavicular line). After 7 years, the lower edge of the liver does not come out from under the costal arch. Only the stomach is located under the liver: from that time on, its skeletotopia almost does not differ from that of an adult. In children, the liver is very mobile, and its position changes easily with a change in body position.
In children of the first 5-7 years of life, the lower edge of the liver always comes out from under the right hypochondrium and is easily palpable. Usually it protrudes 2-3 cm from under the edge of the costal arch along the midclavicular line in a child of the first 3 years of life. From the age of 7, the lower edge is not palpable, and along the midline it should not go beyond the upper third of the distance from the umbilicus to the xiphoid process.
The formation of liver lobules occurs in the embryonic period, developed, but their final differentiation is completed by the end of the first month of life. In children at birth, about 1.5% of hepatocytes have 2 nuclei, while in adults - 8%.
The gallbladder in newborns is usually hidden by the liver, which makes it difficult to palpate and makes its x-ray image fuzzy. It is cylindrical or pear-shaped, rarely spindle-shaped or S-shaped. The latter is due to the unusual location of the hepatic artery. With age, the size of the gallbladder increases.
In children after 7 years, the projection of the gallbladder is located at the point of intersection of the outer edge of the right rectus abdominis muscle with the costal arch and laterally (in the supine position). Sometimes a line is used to determine the position of the gallbladder, connecting the navel to the top of the right armpit. The point of intersection of this line with the costal puff corresponds to the position of the bottom of the gallbladder.
The median plane of the body of a newborn forms an acute angle with the plane of the gallbladder, while in an adult they lie parallel. The length of the cystic duct in newborns varies greatly and is usually longer than the common bile duct. The cystic duct merges with the common hepatic duct at the level of the gallbladder neck to form the common bile duct. The length of the common bile duct is very variable even in newborns (5-18 mm). It increases with age.
The average size of the gallbladder in children (Mazurin A. V., Zaprudnov A. M., 1981)
The secretion of bile begins already in the prenatal period of development. In the postnatal period, due to the transition to enteral nutrition, the amount of bile and its composition undergo significant changes.
During the first half of the year, the child mainly receives a fat diet (about 50% of the energy value of human milk is covered by fat), steatorrhea is often detected, which is explained, along with the limited lipase activity of the pancreas, to a large extent by the lack of bile salts formed by hepatocytes. Especially low is the activity of bile formation in preterm infants. It makes up about 10-30% of bile formation in children at the end of the first year of life. This deficiency is compensated to some extent by the good emulsification of milk fat. The expansion of the set of food products after the introduction of complementary foods and then when switching to a normal diet places increasing demands on the function of bile formation.
The bile of a newborn (up to the age of 8 weeks) contains 75-80% of water (in an adult - 65-70%); more protein, fat and glycogen than adults. Only with age does the content of dense substances increase. The secret of hepatocytes is a golden liquid, isotonic to blood plasma (pH 7.3-8.0). it contains bile acids (mainly cholic, less chenodeoxycholic), bile pigments, cholesterol, inorganic salts, soaps, fatty acids, neutral fats, lecithin, urea, vitamins A, B C, in a small amount some enzymes (amylase, phosphatase, protease , catalase, oxidase). The pH value of cystic bile usually decreases to 6.5 versus 7.3-8.0 of hepatic bile. The final formation of the bile composition is completed in the bile ducts, where a particularly large amount (up to 90%) of water is reabsorbed from the primary bile, Mg, Cl, HCO3 ions are also reabsorbed, but in relatively smaller quantities, which leads to an increase in the concentration of many organic bile components.
The concentration of bile acids in the hepatic bile in children of the first year of life is high, then it decreases by the age of 10, and in adults it increases again. This change in the concentration of bile acids explains the development of subhepatic cholestasis (bile thickening syndrome) in children of the neonatal period.
In addition, the ratio of glycine / taurine is changed in newborns compared with school-age children and adults in whom glycocholic acid predominates. In young children, it is not always possible to detect deoxycholic acid in bile.
Although the liver is relatively large at birth, it is functionally immature. The release of bile acids, which play an important role in the digestion process, is small, which probably often causes steatorrhea (a large amount of fatty acids, soap, neutral fat is detected in the coprogram) due to insufficient activation of pancreatic lipase. With age, the formation of bile acids increases with an increase in the ratio of glycine to taurine due to the latter; at the same time, the liver of a child in the first months of life (especially up to 3 months) has a greater "glycogen capacity" than in adults.
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Ratio |
Acid ratio cholic / chenodeoxycholic / desokencholic |
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limits | |||||
Liver, hepar, is located in the region of the right hypochondrium and in the epigastric region.
Topography of the liver
Secreted from the liver two surfaces: diaphragmatic, faces diaphragmatica, and visceral faces visceralis. Both surfaces form a sharp bottom edge,margo inferior; the posterior edge of the liver is rounded.
To the diaphragmatic surface liver from the diaphragm and the anterior abdominal wall in the sagittal plane is the falciform ligament of the liver, lig. falciforme, representing a duplication of the peritoneum.
on the visceral surface 3 furrows stand out in the liver: two of them go in the sagittal plane, the third - in the frontal.
The left sulcus forms a fissure of the round ligament, fissura ligamenti teretis, and in the back - the gap of the venous ligament, fissura ligamenti venosi. The first fissure contains the round ligament of the liver. lig. teres hepatis. In the gap of the venous ligament is the venous ligament, lig. venosum.
The right sagittal groove in the anterior part forms the fossa of the gallbladder, fossa vesicae fellae, and in the back - the groove of the inferior vena cava, sulcus Venae cavae.
The right and left sagittal grooves are connected by a deep transverse groove, which is called gates of the liverpdrta hepatis.
Lobes of the liver
On the visceral surface of the right lobe of the liver, square share,lobus quadrdtus, And caudate lobe,lobus caudatus. Two processes extend forward from the caudate lobe. One of them is the caudate process, processus caudatus, the other is the papillary process, processus papillaris.
The structure of the liver
The outside of the liver is covered serous membrane,tunica serosa, represented by the visceral peritoneum. A small area in the back is not covered by the peritoneum - this extraperitoneal field,area nude. However, despite this, it can be considered that the liver is located intraperitoneally. Under the peritoneum is a thin dense fibrous membrane,tunica fibrosa(glisson capsule).
Secreted in the liver 2 beats, 5 sectors and 8 segments. In the left lobe, 3 sectors and 4 segments are distinguished, in the right - 2 sectors and also 4 segments.
Each sector represents a section of the liver, which includes a branch of the portal vein of the second order and the corresponding branch of the hepatic artery, as well as nerves, and the sectoral bile duct exits. Under the hepatic segment understand the area of the hepatic parenchyma surrounding the branch of the portal vein of the third order, the branch of the hepatic artery corresponding to it and the bile duct.
Morphofunctional unit liver
is a lobule of the liver lobulus hepatis.
Vessels and nerves of the liver
The porta hepatis enters its own hepatic artery and portal vein.
The portal vein carries venous blood from the stomach, small and large intestine, pancreas and spleen, and the proper hepatic artery carries arterial blood.
Inside the liver, the artery and portal vein branch into interlobular arteries and interlobular veins. These arteries and veins are located between the lobules of the liver along with the bile interlobular ducts.
Wide intralobular sinusoidal capillaries depart from the interlobular veins inside the lobules, lying between the hepatic plates ("beams") and flowing into the central vein.
The arterial capillaries that branch off from the interlobular arteries flow into the initial sections of the sinusoidal capillaries.
The central veins of the hepatic lobules form the sublobular veins, from which large and several small hepatic veins are formed, emerging from the liver in the region of the groove of the inferior vena cava and flowing into the inferior vena cava.
Lymphatic vessels flow into the hepatic, celiac, right lumbar, upper diaphragmatic, parasternal lymph nodes.
Innervation of the liver
carried out by branches of the vagus nerves and the hepatic (sympathetic) plexus.
16.4. LIVER
Liver (hepar)- the largest gland of the digestive tract. The functions of the liver are extremely diverse. Many metabolic products are neutralized in it, hormones, biogenic amines, as well as a number of drugs are inactivated. The liver is involved in the protective reactions of the body against microbes and foreign substances in case of their penetration from the outside. Glycogen is formed in it - the main source of maintaining a constant concentration of glucose in the blood. The most important blood plasma proteins are synthesized in the liver: fibrinogen, albumin, prothrombin, etc. Iron is metabolized here and bile is formed, which is necessary for the absorption of fats in the intestine. It plays an important role in the metabolism of cholesterol, which is an important component of cell membranes. The liver accumulates the necessary
Rice. 16.36. Human liver:
1 - central vein; 2 - sinusoidal capillaries; 3 - liver beams
fat-soluble vitamins for the body - A, D, E, K, etc. In addition, in the embryonic period, the liver is a hematopoietic organ. Such numerous and important functions of the liver determine its importance for the body as a vital organ.
Development. The liver rudiment is formed from the endoderm at the end of the 3rd week of embryogenesis and looks like a saccular protrusion of the ventral wall of the trunk intestine (hepatic bay). In the process of growth, the hepatic bay is divided into the upper (cranial) and lower (caudal) sections. The cranial region serves as a source of development of the liver and hepatic duct, the caudal - of the gallbladder and bile duct. The mouth of the hepatic bay, into which the cranial and caudal sections flow, forms the common bile duct. In histogenesis, divergent differentiation of stem cells occurs in the cranial part of the hepatic bay, as a result of which differons of liver epitheliocytes (hepatocytes) and bile duct epitheliocytes (cholangiocytes) appear. Epithelial cells of the cranial hepatic bay rapidly grow in the mesenchyme of the mesentery, forming numerous strands. Between the epithelial strands is a network of wide blood capillaries originating from the vitelline vein, which in the process of development gives rise to the portal vein.
The glandular parenchyma of the liver formed in this way resembles a sponge in its structure. Further differentiation of the liver occurs in the second half of the intrauterine period of development and in the first years after birth. At the same time, along the branches of the portal vein, connective tissue grows into the liver, dividing it into hepatic lobules.
Structure. The surface of the liver is covered with a connective tissue capsule, which fuses tightly with the visceral sheet of the peritoneum. Parenchyma
Rice. 16.37. The circulatory system of the liver (according to E. F. Kotovsky):
1 - portal vein and hepatic artery; 2 - lobar vein and artery; 3 - segmental vein and artery; 4 - interlobular artery and vein; 5 - perilobular vein and artery; 6 - intralobular hemocapillaries; 7 - central vein; 8 - subdollar vein; 9 - hepatic veins; 10 - hepatic lobule
liver is made up of hepatic lobules (lobuli hepaticus). Hepatic lobules are structural and functional units of the liver (Fig. 16.36).
There are several ideas about their structure. According to the classical view, the hepatic lobules are in the form of hexagonal prisms with a flat base and a slightly convex apex. Their width does not exceed 1.5 mm, while their height, despite significant fluctuations, is somewhat larger. Sometimes simple lobules merge (2 or more) at their bases and form larger complex hepatic lobules. The number of lobules in the human liver reaches 500 thousand. The interlobular connective tissue forms the stroma of the organ. It contains blood vessels and bile ducts, structurally and functionally associated with the hepatic lobules. In humans, the interlobular connective tissue is poorly developed, and as a result, the hepatic lobules are poorly delimited from each other. This structure is characteristic of a healthy liver. On the contrary, the intensive development of connective tissue, accompanied by atrophy (reduction) of the hepatic lobules, is a sign of a severe liver disease known as cirrhosis.
Circulatory system. Based on the classical concept of the structure of the hepatic lobules, the circulatory system of the liver can be conditionally divided into three parts: the system of blood flow to the lobules, the blood circulation system inside them, and the system of blood outflow from the lobules (Fig. 16.37).
The inflow system is represented by the portal vein and the hepatic artery. The portal vein, collecting blood from all unpaired organs of the abdominal cavity, rich in substances absorbed in the intestine, delivers it to the liver. The hepatic artery brings oxygenated blood from the aorta. In the liver, these vessels are repeatedly divided into ever smaller vessels: lobar, segmental, interlobular veins and arteries. (vv. And aa. interlobulares), perilobular veins and arteries (vv. And aa. perilobulares). Throughout these vessels are accompanied by bile ducts similar in name. (ductuli biliferi)
Together, the branches of the portal vein, hepatic artery, and bile ducts make up the so-called hepatic triad. Next to them lie the lymphatic vessels.
Interlobular veins and arteries, subdivided into 8 orders of magnitude, run along the lateral faces of the hepatic lobules. The perilobular veins and arteries extending from them encircle the lobules at different levels.
Interlobular and perilobular veins are vessels with an underdeveloped muscular membrane. However, in the places of branching in their walls, accumulations of muscle elements forming sphincters are observed. The corresponding interlobular and perilobular arteries are of the muscular type. In this case, the arteries are usually several times smaller in diameter than the adjacent veins.
Blood capillaries begin from the perilobular veins and arteries. They enter the hepatic lobules and merge to form intralobular sinusoidal vessels that make up the blood circulation system in the hepatic lobules. Mixed blood flows through them in the direction from the periphery to the center of the lobules. The ratio between venous and arterial blood in the intralobular sinusoidal vessels is determined by the state of the sphincters of the interlobular veins. Intralobular capillaries are sinusoidal (up to 30 μm in diameter) type of capillaries with a discontinuous basement membrane. They go between strands of hepatic cells - hepatic beams, converging radially to the central veins (vv. centrales), which lie in the center of the hepatic lobules.
The central veins begin the system of outflow of blood from the lobules. Upon exiting the lobules, these veins drain into the sublobular veins. (vv. sublobulares), passing through the interlobular septa. The sublobular veins are not accompanied by arteries and bile ducts, that is, they are not part of the triads. On this basis, they are easy to distinguish from the vessels of the portal vein system - interlobular and perilobular veins that bring blood to the lobules.
The central and sublobular veins are non-muscular vessels. They merge and form branches of the hepatic veins, which in the amount of 3-4 leave the liver and flow into the inferior vena cava. Branches of the hepatic veins have well-developed muscular sphincters. With their help, the outflow of blood from the lobules and the entire liver is regulated in accordance with its chemical composition and mass.
Thus, the liver is supplied with blood from two powerful sources - the portal vein and the hepatic artery. Thanks to this, through the liver
Rice. 16.38. Ultramicroscopic structure of the liver (according to E. F. Kotovsky): 1 - intralobular sinusoidal vessel; 2 - endothelial cell; 3 - sieve areas; 4 - stellate macrophages; 5 - perisinusoidal space; 6 - reticular fibers; 7 - microvilli of hepatocytes; 8 - hepatocytes; 9 - bile capillary; 10 - perisinusoidal fat-accumulating cells; 11 - fatty inclusions in the cytoplasm of a fat-accumulating cell; 12 - erythrocytes in the capillary
in a short time, all the blood of the body passes, being enriched with proteins, freeing itself from the products of nitrogen metabolism and other harmful substances. The liver parenchyma has a huge number of blood capillaries, and as a result, the blood flow in the liver lobules is slow, which contributes to the exchange between blood and liver cells that perform protective, neutralizing, synthetic and other important functions for the body. If necessary, a large mass of blood can be deposited in the vessels of the liver.
Classic liver lobule(lobulus hepaticus classicus seu poligonalis). According to the classical view, the hepatic lobules are formed hepatic beams And intralobular sinusoidal blood capillaries. Liver beams built from hepatocytes- hepatic epitheliocytes, located in the radial direction. Between them in the same direction from the periphery to the center of the lobules pass blood capillaries.
Intralobular blood capillaries are lined with flat endotheliocytes. There are small pores in the area of connection of endothelial cells with each other. These areas of the endothelium are called sieve (Fig. 16.38).
Rice. 16.39. The structure of the sinusoid of the liver:
1 - stellate macrophage (Kupffer cell); 2 - endotheliocyte: A- pores (network zone); 3 - perisinusoidal space (Disse space); 4 - reticular fibers; 5 - fat-accumulating cell with lipid drops (b); 6 - pit cell (hepatic NK cell, granular lymphocyte); 7 - tight contacts of hepatocytes; 8 - desmosome of hepatocytes; 9 - bile capillary (according to E. F. Kotovsky)
Numerous stellate macrophages (Kupffer cells), which do not form a continuous layer, are scattered between endotheliocytes. Unlike endotheliocytes, they are monocytic in origin and are liver macrophages. (macrophagocytus stellatus), with which its protective reactions are associated (phagocytosis of erythrocytes, participation in immune processes, destruction of bacteria). Star-shaped macrophages have a process shape and structure typical of phagocytes. Pit cells (pit cells, hepatic NK cells) are attached to stellate macrophages and endothelial cells from the side of the lumen of the sinusoids using pseudopodia. In their cytoplasm, in addition to organelles, there are secretory granules (Fig. 16.39). These cells belong to large granular lymphocytes, which have natural killer activity and at the same time endocrine
function. Due to this, hepatic NK cells, depending on the conditions, can perform opposite effects: for example, in liver diseases, they, like killers, destroy damaged hepatocytes, and during the recovery period, like endocrinocytes (apudocytes), they stimulate the proliferation of hepatic cells. The main part of NK cells is located in the zones surrounding the vessels of the portal tract (triads).
The basement membrane is absent over a large extent in intralobular capillaries, with the exception of their peripheral and central sections. The capillaries are surrounded by narrow (0.2-1 µm) perisinusoidal space(Disse). Through the pores in the endothelium of the capillaries, the components of the blood plasma can enter this space, and in conditions of pathology, formed elements also penetrate here. In it, in addition to a liquid rich in proteins, there are microvilli of hepatocytes, sometimes processes of stellate macrophages, argyrophilic fibers braiding the hepatic beams, as well as processes of cells known as fat-accumulating cells. These small (5-10 µm) cells are located between adjacent hepatocytes. They constantly contain small drops of fat that do not merge with each other, many ribosomes and single mitochondria. The number of fat-accumulating cells can increase dramatically in a number of chronic liver diseases. It is believed that these cells, like fibroblasts, are capable of fiber formation, as well as the storage of fat-soluble vitamins. In addition, the cells are involved in the regulation of the lumen of the sinusoids and secrete growth factors.
Hepatic beams consist of hepatocytes connected to each other by desmosomes and in a "lock" type. The beams anastomose with each other, and therefore their radial direction in the lobules is not always clearly visible. In the hepatic beams and anastomoses between them, hepatocytes are located in two rows, closely adjacent to each other. In this regard, in the cross section, each beam appears to consist of two cells. By analogy with other glands, hepatic beams can be considered the terminal sections of the liver, since the hepatocytes that form them secrete glucose, blood proteins, and a number of other substances.
Between the rows of hepatocytes that make up the beam, there are bile capillaries, or tubules, with a diameter of 0.5 to 1 micron. These capillaries do not have their own walls, as they are formed by contiguous biliary surfaces of hepatocytes, on which there are small depressions that coincide with each other and together form the lumen of the bile capillary (Fig. 16.40, a, b). The lumen of the bile capillary does not communicate with the intercellular gap due to the fact that the membranes of neighboring hepatocytes in this place fit tightly to each other, forming the endplates. The surfaces of hepatocytes, limiting the bile capillaries, have microvilli that protrude into their lumen.
It is believed that the circulation of bile through these capillaries (tubules) is regulated by microfilaments located in the cytoplasm of hepatocytes around the lumen of the tubules. With the inhibition of their contractility in the liver, cholestasis may occur, i.e. stagnation of bile in the tubules and ducts. On conventional histological preparations, bile capillaries
Rice. 16.40. The structure of the lobules (a) and beams (b) of the liver (according to E. F. Kotovsky): A- diagram of the structure of the portal lobule and acinus of the liver: 1 - classical hepatic lobule; 2 - portal lobule; 3 - hepatic acinus; 4 - triad; 5 - central veins; b- diagram of the structure of the hepatic beam: 1 - hepatic beam (plate); 2 - hepatocyte; 3 - blood capillaries; 4 - perisinusoidal space; 5 - fat-accumulating cell; 6 - bile duct; 7a - around-lobular vein; 7b - perilobular artery; 7 in- perilobular bile duct; 8 - central vein
remain invisible and are detected only with special processing methods (silver impregnation or injection of capillaries with a stained mass through the bile duct). On such preparations, it is clear that the bile capillaries blindly begin at the central end of the hepatic beam, go along
her, slightly bending and giving to the sides short blind outgrowths. Closer to the periphery, lobules form bile ducts(cholangiols, Hering's tubules), the wall of which is represented by both hepatocytes and epitheliocytes (cholangiocytes). As the caliber of the groove increases, its wall becomes continuous, lined with a single-layer epithelium. It contains poorly differentiated (cambial) cholangiocytes. Cholangiols flow into interlobular bile ducts (ductuli interlobulares).
Thus, the bile capillaries are located inside the hepatic beams, while blood capillaries pass between the beams. Therefore, each hepatocyte in the hepatic beam has two sides. One side - biliary- facing the lumen of the bile capillary, where the cells secrete bile (exocrine type of secretion), the other - vascular- directed to the blood intralobular capillary, into which cells secrete glucose, urea, proteins and other substances (endocrine type of secretion). There is no direct connection between the blood and bile capillaries, since they are separated from each other by hepatic and endothelial cells. Only in diseases (parenchymal jaundice, etc.) associated with damage and death of part of the liver cells, bile can enter the blood capillaries. In these cases, bile is carried by the blood throughout the body and stains its tissues yellow (jaundice).
According to another point of view on the structure of the hepatic lobules, they consist of wide plates (laminae hepaticae), anastomosing with each other. Between the plates are blood lacunae (vas sinusoidem), through which blood circulates slowly. The wall of lacunae is formed by endotheliocytes and stellate macrophagocytes. They are separated from the plates by the perilacunar space.
There are ideas about the histofunctional units of the liver, different from the classic hepatic lobules. As such, the so-called portal hepatic lobules and hepatic acini are considered. Portal lobule (lobulus portalis) includes segments of three adjacent classical hepatic lobules surrounding the triad. Therefore, it has a triangular shape, in its center lies a triad, and on the periphery, that is, in the corners, there are veins (central). In this regard, in the portal lobule, the blood flow through the blood capillaries is directed from the center to the periphery (see Fig. 16.40, a). Hepatic acinus (acinus hepaticus) formed by segments of two adjacent classical lobules, due to which it has the shape of a rhombus. At its sharp corners, veins (central) pass, and at an obtuse angle - a triad, from which its branches (around the lobules) go inside the acinus. From these branches, hemocapillaries are sent to the veins (central) (see Fig. 16.40, A). Thus, in the acinus, as well as in the portal lobule, the blood supply is carried out from its central sections to the peripheral ones.
hepatic cells, or hepatocytes, make up 60% of all cellular elements of the liver. They perform most of the functions inherent in the liver. Hepatocytes have an irregular polygonal shape. Their diameter reaches 20-25 microns. Many of them (up to 20% in the human liver) contain two or more nuclei. The number of such cells depends on the functional
Rice. 16.41. Hepatocyte. Electron micrograph, magnification 8000 (preparation of E. F. Kotovsky):
1 - core; 2 - mitochondria; 3 - granular endoplasmic reticulum; 4 - lysosome; 5 - glycogen; 6 - border between hepatocytes; 7 - bile capillary; 8 - desmo-soma; 9 - connection according to the type of "lock"; 10 - agranular endoplasmic reticulum
body conditions: for example, pregnancy, lactation, starvation noticeably affect their content in the liver (Fig. 16.41).
The nuclei of hepatocytes are round in shape, their diameter ranges from 7 to 16 microns. This is due to the presence in the liver cells, along with the usual nuclei (diploid), larger ones - polyploid. The number of these nuclei gradually increases with age and reaches 80% by old age.
The cytoplasm of liver cells is stained not only with acidic, but also with basic dyes, as it has a high content of RNP. It contains all kinds of common organelles. The granular endoplasmic reticulum looks like narrow tubules with attached ribosomes. In centrilobular cells, it is located in parallel rows, and
in the peripheral - in different directions. The agranular endoplasmic reticulum in the form of tubules and vesicles occurs either in small areas of the cytoplasm or is scattered throughout the cytoplasm. The granular type of the network is involved in the synthesis of blood proteins, and the agranular one is involved in the metabolism of carbohydrates. In addition, the endoplasmic reticulum, due to the enzymes formed in it, detoxifies harmful substances (as well as inactivates a number of hormones and drugs). Peroxisomes are located near the tubules of the granular endoplasmic reticulum, with which the metabolism of fatty acids is associated. Most mitochondria are round or oval and 0.8–2 µm in size. Less common are filamentous mitochondria, the length of which reaches 7 μm or more. Mitochondria are distinguished by a relatively small number of cristae and a moderately dense matrix. They are evenly distributed in the cytoplasm. The number of them in one cell may vary. The Golgi complex during the period of intense bile secretion moves towards the lumen of the bile capillary. Around it there are separate or small groups of lysosomes. There are microvilli on the vascular and biliary surfaces of cells.
Hepatocytes contain various kinds of inclusions: glycogen, lipids, pigments and others, formed from products brought by the blood. Their number varies in different phases of liver activity. Most easily, these changes are found in connection with the processes of digestion. Already 3-5 hours after a meal, the amount of glycogen in hepatocytes increases, reaching a maximum after 10-12 hours. 24-48 hours after a meal, glycogen, gradually turning into glucose, disappears from the cell cytoplasm. In those cases when the food is rich in fats, drops of fat appear in the cytoplasm of the cells, and first of all - in the cells located on the periphery of the hepatic lobules. In some diseases, the accumulation of fat in cells can turn into their pathological condition - obesity. The processes of obesity of hepatocytes are sharply manifested in alcoholism, brain injuries, radiation sickness, etc. In the liver, a daily rhythm of secretory processes is observed: bile secretion predominates during the day, and glycogen synthesis predominates at night. Apparently, this rhythm is regulated with the participation of the hypothalamus and pituitary gland. Bile and glycogen are formed in different zones of the hepatic lobule: bile is usually produced in the peripheral zone, and only then this process gradually spreads to the central zone, and glycogen is deposited in the opposite direction - from the center to the periphery of the lobule. Hepatocytes continuously secrete glucose, urea, proteins, fats into the blood, and bile into the bile capillaries.
bile ducts. These include the intrahepatic and extrahepatic bile ducts. The intrahepatic include the interlobular bile ducts, and the extrahepatic include the right and left hepatic ducts, the common hepatic, cystic and common bile ducts. The interlobular bile ducts, together with the branches of the portal vein and the hepatic artery, form triads in the liver. The wall of the interlobular ducts consists of a single-layer cubic, and in larger ducts - of a cylindrical epithelium, equipped with a border, and a thin layer of loose connective tissue. In the apical sections of the epithelial cells of the ducts, there are often
tea in the form of grains or drops components of bile. On this basis, it is assumed that the interlobular bile ducts perform a secretory function. The hepatic, cystic and common bile ducts have approximately the same structure. These are relatively thin tubes with a diameter of about 3.5-5 mm, the wall of which is formed by three shells. mucous membrane consists of a single layer of high prismatic epithelium and a well-developed layer of connective tissue (lamina propria). The epithelium of these ducts is characterized by the presence of lysosomes and inclusions of bile pigments in its cells, which indicates a resorptive, i.e., absorption, function of the epithelium of the ducts. In the epithelium, endocrine and goblet cells are often found. The number of the latter increases sharply in diseases of the biliary tract. own record The mucous membrane of the bile ducts is distinguished by the richness of elastic fibers located longitudinally and circularly. In a small amount, it contains mucous glands. Muscular membrane thin, consists of spirally arranged bundles of smooth myocytes, between which there is a lot of connective tissue. The muscular membrane is well expressed only in certain parts of the ducts - in the wall of the cystic duct when it passes into the gallbladder and in the wall of the common bile duct when it flows into the duodenum. In these places, bundles of smooth myocytes are located mainly circularly. They form sphincters that regulate the flow of bile into the intestines. adventitial sheath composed of loose connective tissue.
Histology, embryology, cytology: textbook / Yu. I. Afanasiev, N. A. Yurina, E. F. Kotovsky and others; ed. Yu. I. Afanasiev, N. A. Yurina. - 6th ed., revised. and additional - M. : GEOTAR-Media, 2014. - 800 p. : ill.