Extrahepatic biliary system includes:
Ø common hepatic duct, formed from the confluence of the right and left hepatic ducts. At the confluence of the hepatic ducts, concentric accumulations of muscle fibers form the Mirizi sphincter;
Ø gallbladder and its cystic duct with Lutkens sphincter;
Ø common bile duct (CBD), starting from the junction of the hepatic and cystic ducts;
Ø hepato-pancreatic ampoule (ampulla of the large duodenal papilla - BDS) with the sphincter of Oddi.
Gall bladder sometimes in newborns it has a fusiform, and subsequently pear-shaped or funnel-shaped, with age, the size of the gallbladder increases. In newborns, the average length is 3.4 cm, in adults - 9 cm, volume - 50 ml. The bottom of the gallbladder is located in front, the body passes into a narrow neck and cystic duct.
In the area of the neck of the gallbladder at the place of transition to the cystic duct there is sphincter of Lutkens in the form of circular muscle fibers. The neck of the gallbladder has a lumen of 0.7 - 0.8 cm, in the region of the neck and cystic duct there are spiral folds - Heister flaps. Saccular expansion of the gallbladder neck is called Hartman's pocket. The curvature of the cystic duct follows from top to bottom and inwards, resulting in an angle with the gallbladder. The gallbladder enlarges. spindle-shaped, and subsequently pear-shaped or funnel-shaped, with age, the size
The length of the CBD is 8-12 cm, the diameter is 0.5-1 cm, with ultrasound - 0.2-0.8 cm. The CBD opens into the lumen of the duodenum (DPC) in the region of the greater duodenal papilla. The distal end of the CBD is widened, and there is a layer of smooth muscle in its wall. Before flowing into the duodenum, the CBD in 80% of cases merges with the Wirsung duct of the pancreas. Sphincter of Oddi- this is a fibromuscular formation surrounding the end sections of the CBD and the Wirsung duct, as well as their canal in the thickness of the duodenal wall.
Currently, this sphincter mechanism is recognized as responsible for the regulation of bile secretion and emptying of the gallbladder, as well as the protection of the extrahepatic biliary system from infection with duodenal contents. The intramural part of the CBD has a length of 1-2 cm, when passing through the muscular layer of the duodenum, the lumen of the duct narrows, after which a funnel-shaped expansion, called the ampulla of Vater, is formed. The sphincter of Oddi also includes the common sphincter of the ampoule - the sphincter of Westphal.
The wall of the gallbladder is represented by muscle and elastic fibers without clearly defined layers, their orientation is very different. The mucous membrane of the gallbladder is folded, does not contain glands, has depressions that penetrate into the muscle layer (Lyushka's crypts) and invaginations reaching the serous membrane. The walls of the gallbladder are easily extensible, its size and capacity vary depending on conditions and pathology.
The main functions of the gallbladder:
Ø concentration and deposition of bile between meals;
Ø evacuation of bile by contraction of the smooth muscle wall in response to stimulating impulses;
Ø maintaining hydrostatic pressure in the biliary tract.
The gallbladder has the ability to concentrate bile tenfold, resulting in the formation of gallbladder, isotonic to plasma bile, but containing higher concentrations of Na, K, Ca, bile acids and lower concentrations of chlorides and bicarbonates than hepatic bile.
The contraction can be either of the entire bubble or of its individual parts; contraction in the area of the body and bottom causes a simultaneous expansion of the neck. With the contraction of the entire bubble in the body, an increase in pressure develops up to 200 - 300 mm in diameter. Art.
The tone of the CBD sphincters outside the digestion is increased; under the influence of cholecystokinin, which causes a simultaneous contraction of the gallbladder and relaxation of the sphincter of Oddi, bile is released into the duodenum. The reflexogenic zone for the sphincter of Oddi is the duodenum. The activity of the sphincter devices is strictly synchronized with the rhythm sensor detected at the level of the CBD opening.
Biliary system is intended for the removal into the intestine of a physiologically important secretion of hepatocytes - bile, which has a complex composition and performs a number of special functions: participation in the digestion and absorption of lipids in the intestine, the transfer of a number of physiologically active substances into the intestine for subsequent absorption and use in general metabolism, as well as some end products of metabolism intended for release into the external environment.
General diagram of the structure of the biliary system... The anatomy of the biliary system has been well studied by now. Intrahepatic ducts from the left square and caudate lobes of the liver, merging, form the left hepatic duct (ductus hepaticus sinister). The intrahepatic ducts of the right lobe of the liver form the right hepatic duct (ductus hepaticus dexter).
The right and left hepatic ducts join and form a common hepatic duct (ductus hepaticus communis), into which the cystic duct (ductus cysticus) flows, connecting the bile duct system with the gallbladder (vesica felleae), which is a reservoir for the accumulation of bile. After joining the common hepatic and cystic ducts, a common bile duct (ductus choledochus) is formed.
The common bile duct flows into the duodenum (most often in the middle third of its descending part), moreover, not just into the intestinal wall, but into the center of a special "papillary swelling" (papilla duodeni major, nipple vater, duodenal papilla). Before this, in most cases (about 75%), the end part of the common bile duct connects with the main pancreatic duct, at the site of their confluence, an ampoule-like expansion of the nipple of Vater is formed, in which bile and pancreatic juice are mixed, which has a certain physiological significance.
In the wall of the duodenal papilla there are annular smooth muscle fibers that form a sphincter (sphincter of the hepato-pancreas of the large duodenal papilla, sphincter of Oddi), which performs an important function: on the one hand, it regulates the flow of bile and pancreatic juice into the duodenum, providing an economical supply of these valuable secretions mainly during the digestion phase. On the other hand, this sphincter prevents the return of duodenal contents into the main pancreatic and common bile ducts.
In some pathological conditions, for example, with dyskinesia of the duodenum, after surgical interventions in the area of the duodenal papilla, etc., such a return flow is possible, but fraught with adverse consequences, it is possible to throw active digestive enzymes, food particles, microflora with the development of subsequent inflammatory complications - cholangitis and pancreatitis. The nearest fold of the duodenal mucosa, hanging over the opening of the duodenal papilla, to some extent creates an additional obstacle for the reflux of intestinal contents into its ampoule.
It should be noted that all parts of the biliary system are often anatomically very variable (the number of hepatic ducts, the length of individual sections, the junction, location, etc.), which should be taken into account when performing some diagnostic studies.
The extrahepatic bile ducts have almost the same structure. The wall of the bile ducts consists of mucosa, muscular (fibromuscular) and serous membranes, their severity and thickness increase in the distal direction. The wall consists of a single-layer high prismatic epithelium (with separate goblet cells), a connective tissue layer containing a large number of elastic fibers located longitudinally and circularly, and smooth muscle bundles located in the outer layer (small muscle bundles are also located in the inner layers).
A pronounced muscle layer is determined in the wall of the cystic and especially the common bile duct (muscle fibers are located longitudinally and mainly circularly). Muscle bundles of the sphincter of Oddi partly annularly cover the end part of the common bile duct, partly - the end part of the excretory duct of the pancreas, and their main part surrounds these ducts after they merge. In addition, the submucosal layer of the apex of the duodenal papilla also contains a thin circular layer of smooth muscle fibers.
The outer membrane of the ducts is formed by loose connective tissue, in which the vessels and nerves are located. The inner surface of the ducts is mostly smooth, but in some areas there are folds, for example, a spiral fold (plica spiralis) in the cystic duct. Some anatomists and histologists in the cystic duct (ductus cysticus) distinguish: cervical, intermediate, semilunar, spiral Geister (Heistery) and terminal valves (which are clearly identified, however, not always). Several pocket-like folds are found in the distal part of the common bile duct.
Along the course of the bile ducts there are several sphincters or sphincter-like formations: the Mirizzi sphincter - when the right and left hepatic ducts merge, Lutkens' spiral sphincter - a circular bundle of smooth muscle fibers in the neck of the gallbladder - at the junction of the neck into the cystic duct, the sphincter of the distal part of the common bile duct sphincter of Oddi.
The significance of the system of these folds of the mucous membrane, sphincters and sphincter-like formations is to prevent the reverse (retrograde) flow of bile and sometimes (mainly in pathological conditions - with vomiting, duodenal dyskinesia, etc.) entering the common bile duct of duodenal contents and pancreatic juice, and therefore, in preventing the possibility of inflammatory damage to the ducts in this way.
The mucous membrane of the bile ducts has both absorptive and secreting ability. The length of the common hepatic duct is 2-6 cm, the diameter is from 3 to 9 mm. Sometimes it is absent, and the right and left hepatic ducts merge directly with the cystic duct, forming a common bile duct. The length of the cystic duct is 3-7 cm, the width is about 6 mm. The common bile duct is usually about 2-9 cm long and 5-9 mm in diameter.
In previous years, there was an opinion that after a cholecystectomy operation (for example, for cholelithiasis), the common bile duct to some extent "takes over" the function of a "bile reservoir" (for the purpose of its economical consumption, mainly during periods of digestion) and its diameter increases, sometimes doubled. Since the rate of advancement of bile in this dilated section of the biliary system is noticeably reduced, this has clinical significance: with a predisposition, gallstones are formed again in the dilated duct.
In the last decade, this opinion has been abandoned. Dilation of the common bile duct after cholecystectomy is most often associated with the presence of stenosing duodenal papillitis. Therefore, surgeons performing cholecystectomy often combine this operation with papillosphincterotomy or the imposition of an additional choledochoduodenoanastomosis.
The common bile duct passes between the sheets of the peritoneum along the free edge of the hepato-duodenal ligament, usually to the right of the portal vein, then passes across the posterior surface of the upper-horizontal part of the duodenum, lies between its descending part and the head of the pancreas, penetrates into the wall of the duodenum and in most cases , connecting with the pancreatic duct, flows into the hepato-pancreas ampulla of the large duodenal papilla.
Occasionally, the distal part of the common bile duct, before flowing into the hepato-pancreas ampulla, passes at some distance not from behind, but through the thickness of the head of the pancreas. In this case, the symptoms of compression of the bile duct by the inflammatory or tumor-altered pancreas appear earlier and more pronounced.
Sometimes the common bile and pancreatic ducts do not merge and do not form an ampulla, but open on the large duodenal papilla with separate openings; other options are also possible (for example, the fusion of the common bile duct with an accessory pancreatic duct). Knowledge of the details of the anatomical structure and location of the bile ducts is of some importance in analyzing the causes of specific features of diseases of the biliary system.
Innervation of the biliary tract is carried out by branches of the hepatic nerve plexus, blood supply - by small branches of its own hepatic artery, venous outflow goes into the portal vein, lymph outflow - to the hepatic lymph nodes of the hepatic portal. Congenital enlargement of the common bile duct, diverticula, and duct doubling have been described as abnormalities observed in adults.
Gall bladder- part of the biliary system, a small hollow organ that serves to accumulate bile during the interdigestive period, concentrate it and release concentrated bile during food intake and digestion. It is a thin-walled pear-shaped sac (its dimensions are very variable - length 5-14 cm, maximum diameter 3.5-4 cm), containing about 30-70 ml of bile. Since the wall of the gallbladder (without pronounced sclerotic changes due to chronic cholecystitis and adhesions to the surrounding organs) is easily extensible, its capacity in some individuals can be much larger, reaching 150-200 ml or more.
The gallbladder is adjacent to the lower surface of the liver, located in the fossa of the gallbladder, in some cases, the gallbladder is completely immersed in the liver parenchyma. In the gallbladder, the bottom, body and neck (passing into the cystic duct) are distinguished. The bottom of the gallbladder is directed anteriorly, in most of the examined it is located slightly below the anterior edge of the liver and often comes into contact with the anterior abdominal wall just below the edge of the costal arch, at the outer edge of the right rectus abdominis muscle.
The body of the gallbladder is directed posteriorly, the neck in most cases (about 85%) - posteriorly, upward and to the left, while the transition of the body to the neck of the bladder occurs at a certain, sometimes rather acute, angle. The upper wall of the gallbladder is adjacent to the liver, separated from it by a layer of loose connective tissue; lower, free, covered with peritoneum, adjacent to the pyloric region of the stomach, the upper-horizontal part of the duodenum and the transverse colon.
These features of the location of the gallbladder explain the possibility of fistulas from the gallbladder (with purulent inflammation, wall necrosis or the formation of pressure ulcers with overflow of the gallbladder with calculi and constant pressure of one or more stones on the mucous membrane of the bladder) in the adjacent wall of these parts of the digestive system.
The shape and location of the gallbladder often have significant individual variations. In rare cases, agenesis (congenital underdevelopment) or doubling of the gallbladder is observed.
The wall of the gallbladder consists of three membranes: mucous, muscular and connective tissue; its lower wall is covered with a peritoneum. The mucous membrane of the gallbladder has multiple folds (which, to a certain extent, allows the gallbladder to stretch significantly when bile overflows and to contract). Numerous protrusions of the mucous membrane of the gallbladder between the muscle bundles of the wall are called crypts, or sinuses of Rokitansky-Ashoff.
In the wall of the gallbladder are also located blindly ending with bulbous extensions at the ends, often branched, tubules - "Lushka's passages". Their functional purpose is not entirely clear, but crypts and "Lushka's passages" can be a place of accumulation of bacteria (and many types of bacteria are secreted from the blood with bile) with the subsequent occurrence of an inflammatory process, as well as a place of intramural stone formation. The surface of the mucous membrane of the gallbladder is covered with tall prismatic epithelial cells (on the apical surface of which there is a mass of microvilli, which explains their significant ability to absorb); it has been proven that these cells also have a secretory capacity.
There are individual cells with a darker coloration of the nucleus and cytoplasm, and with inflammation of the gallbladder, so-called pencil cells are also found. Epithelial cells are located on the "subepithelial layer" - the "own layer of the mucous membrane". In the area of the neck of the gallbladder, there are alveolar-tubular glands that produce mucus.
The innervation of the gallbladder comes from the hepatic nerve plexus, formed by nerve branches from the celiac and gastric plexuses, from the anterior vagus trunk and phrenic nerves.
The blood supply to the gallbladder is carried out from the biliary artery, which in 85% of cases extends from its own hepatic artery, in rare cases - from the common hepatic artery. Veins of the gallbladder (usually 3-4) flow into the intrahepatic branch of the portal vein. The outflow of lymph is carried out into the hepatic lymph nodes located in the neck of the gallbladder and at the gate of the liver.
The function of the biliary system was studied by G. G. Bruno, N. N. Kladnitsky, I. T. Kurtsin, P. K. Klimov, L. D. Lindenbraten and many other physiologists and clinicians. The movement of bile through the bile capillaries, intra- and extrahepatic ducts is carried out primarily under the influence of the total pressure formed by the secretion of bile by hepatocytes, which can reach approximately 300 mm of water. Art.
Further advancement of bile along the larger bile ducts, especially the extrahepatic ones, is determined by their tone and peristalsis, the state of the tone of the sphincter of the hepato-pancreatic ampulla (sphincter of Oddi). The filling of the gallbladder with bile depends on the level of bile pressure in the common bile duct and the tone of the Lutkens sphincter.
There are 3 types of gallbladder contractions:
- small rhythmic with a frequency of 3-6 times every 1 minute in the extra-digestive period;
- peristaltic of various strength and duration, combined with rhythmic;
- strong tonic contractions during digestion, causing a significant portion of concentrated bile to enter the common bile duct and then into the duodenum.
The time from the beginning of a meal to the contractile (tonic) reaction of the gallbladder ("latent period") depends on the nature of the food and ranges from 1 / 2-2 to 8-9 minutes. The flow of bile into the duodenum coincides with the time of passage of the peristaltic wave through the pylorus. The time of tonic contraction of the gallbladder depends on the volume and quality of the food taken. With a plentiful meal, especially a fatty one, the contraction of the gallbladder lasts until the stomach is completely empty.
When eating a small amount of food, especially with a low fat content, the contraction of the gallbladder is short-lived. Of the nutrients taken in approximately equivalent in calorie weight quantities, the strongest contraction of the gallbladder is caused by egg yolks, contributing (in healthy individuals) to the secretion of up to 80% of the bile contained in the bladder from the bladder.
After contraction, the tone of the gallbladder decreases and the period of its filling with bile begins. The locking mechanism of the cystic duct is constantly functioning, either opening the access of a small amount of bile into the bladder, then causing its backflow into the duct system. These changes in the direction of the flow of bile alternate every 1-2 minutes.
In the daytime, a person has an alternation of periods of emptying and accumulation of the gallbladder during meals and at intermediate intervals; at night, a significant amount of bile accumulates and concentrates in it.
Regulation of the functions of the gallbladder and ducts(as well as other parts of the digestive system) is carried out by the neurohumoral route. The gastrointestinal hormone cholecystokinin (pancreozymin) stimulates contraction of the gallbladder and relaxation of the sphincter of Oddi, the secretion of bile by hepatocytes (as well as pancreatic enzymes and bicarbonates).
Cholecystokinin is secreted by special cells (J-cells) of the mucous membrane of the duodenum and jejunum when the products of the breakdown of proteins and fats enter and act on the mucous membrane. Certain hormones of the endocrine glands (ACTH, corticosteroids, adrenaline, sex hormones) affect the function of the gallbladder and biliary tract.
Cholinomimetics increase the contraction of the gallbladder, anticholinergic and adrenomimetic substances - inhibit. Nitroglycerin relaxes the sphincter of Oddi and reduces the tone of the bile ducts, and therefore emergency doctors sometimes use it to relieve an attack of biliary colic (at least for a short time, alleviating the suffering of the patient during his transportation to the hospital). Morphine increases the tone of the sphincter of Oddi, and therefore its administration is contraindicated if an attack of biliary colic is suspected.
Bile acids are formed in the smooth endoplasmic reticulum and mitochondria of hepatocytes from cholesterol. It is believed that NADP, ATP are involved in this process. Bile acids are then actively transported to the intercellular tubules. The secretion of bile acids is carried out through the microvilli and is regulated by Na / K-ATPase. The secretion of water and some ions into the bile ducts occurs mainly passively and depends on the concentration of bile acids. However, in the interlobular ducts, a certain amount of water and ions also enters the bile. It is assumed that the enzyme Ha4 / K + -ATPase plays an important role in this process.
The secretion of water and electrolytes also occurs in the bile ducts, but there may also be a reverse process (absorption), which is manifested in a more pronounced form in patients after cholecystectomy. Thus, ultimately, bile consists of two fractions: hepatocellular and ductal. Secretin causes an increase in the volume of bile, increases the content of bicarbonates and chlorides in it.
O.A. Sablin, V.B. Grinevich, Yu.P. Uspensky, V.A. Ratnikov
Bile is an indispensable participant in the process of food hydrolysis, acts as a regulatory unit in the mechanisms of regulation of the functions of the stomach and intestines, the content of enzymes and hydrochloric acid in gastric juice. Bile also has digestive functions: excretions are excreted with it, it participates in interstitial metabolism. Bile synthesis is continuous. It enters the bile ducts under a pressure of 240-300 mm of water. Art. The liver secretes about 500-2000 ml of bile per day. Bile secretion is performed by parenchymal cells of the liver (75% of its acid-dependent and acid-independent fraction), epithelial cells of the bile ducts (25%). The bile duct fraction is formed by epithelial cells, which enrich the liquid with bicarbonates and chlorine simultaneously with the reabsorption of water and electrolytes from the canalicular bile.
The formation of bile is due to transport from blood plasma, diffusion through the sinusoidal membrane into the hepatocyte of water, ions, and secretion of bile acids by hepatocytes. It is provided by Na-independent active process, energy of aerobic respiration of substrates, which are formed during glycolysis of carbohydrates, oxidation of lipids and lactic acid in the blood. In the mitochondria of hepatocytes and outside of them, bile acids are formed from cholesterol with the participation of ATP. Hydroxylation during the formation of cholic acid is carried out in the endoplasmic reticulum of the hepatocyte. Recently, great importance in the synthesis of bile acids has been attributed to the ion transport system.
It should be recalled that in the composition of the newly synthesized bile acids secreted into the gut, the bile is not more than 10%, the rest of the acid pool is a product of the enterohepatic circulation of bile acids from the gut into the blood and liver. The main energy expended by the hepatocyte is used for the transport of acids and bile through its plasma membrane by the Na-dependent or Na-conjugated (taurocholate) transport system. The precursor of bile acids is lipoprotein cholesterol. Almost all (90%) bile acids are nothing more than hydroxyl derivatives of 5-cholanic acid.
Cholic, chenodeoxycholic and lithocholic acids are synthesized in the liver. Deoxycholic acid is formed due to the activity of the intestinal microflora. Most of the bile acids in the blood are associated with albumin and blood lipoproteins. The absorption of bile acids by liver cells is carried out using a membrane protein that acts as a receptor and carrier. The number of receptors and the activity of Na +, K + -ATPase of the cell membrane, which maintains the Na + concentration gradient, is regulated by the bile acids themselves. Having overcome the sinusoidal membrane, bile acids move in the cytosol from the membrane region to others: either by free diffusion, or by means of intracellular transport, or by means of intracellular structures, by the movement of vesicles.
Most of the transport proteins belong to the glutathione S-transferase family. Of these, the anion-binding protein ligandin and glutathione S-transferase are the main intracellular proteins of the hepatocyte that bind lithocholic acid. In the cytosol of the hepatocyte, glutathione S-transferase reduces the concentration of free bile acids, which facilitates the transmembrane transfer of bile acids from the blood to the hepatocyte. In addition, it prevents the leakage of bile acids from the hepatocyte through the sinusoidal membrane back into the blood, participates in the process of transport of bile acids from the sinusoidal membrane of the hepatocyte to the endoplasmic reticulum, and then to the Golgi apparatus.
From the Golgi apparatus to the canalicular membrane, bile acids move by directed vesicular transfer. Several mechanisms of intracellular transport of bile acids have been shown: free diffusion, directed vesicular transport, and specific transport proteins. Bile acids also penetrate through the canalicular membrane of the hepatocyte into the canal cavity in several ways, this is either a voltage-dependent process in the presence of a specific carrier - a glycoprotein transport protein with a molecular weight of 100 kDa, or it is vesicle exocytosis, and it is a Ca ++ -dependent process, or bile acids from the vesicles they enter the cavity of the bile canals through microtubules and microfilaments, and then the mechanism of the contractile activity of the bile canals is important. Hence, the action of cytochalasin B and cytochalasin D, which block the connection of microfilaments with the canalicular membrane or colchicine and vinblastine, is understandable. The regulators of the contractile activity of the bile canals are the bile acids themselves.
The mechanism of formation of an acid-independent fraction of bile is based on the active transport of sodium into the lumen of the bile tubules by Na +, K + -ATPase of hepatocyte membranes. According to this hypothesis, Na + enters the hepatocyte through the sinusoidal membrane and carries with it chlorine ions, while most of the Na + entering the cell is sent to the blood by Na +, K + -ATPase, which entails an increase in the intracellular concentration of Cl -. In this case, the electrochemical equilibrium is disturbed. According to the electrochemical gradient, chlorine ions pass through the canalicular membrane from the hepatocyte and thereby increase the flow of water and electrolytes from the liver cells into the lumen of the bile ducts. Another hypothesis is based on the leading role in the secretion of the acid-independent fraction of bile - bicarbonates, which, according to the osmotic gradient, increase the flow of water and electrolytes from the liver to bile. The mechanism of secretion of HCO 3 - by hepatocytes is associated with the transport of protons by H + -ATPase or Na + / H + exchange.
The intensity of bile formation is determined by the osmotic properties of bile proteins, the concentration of which in bile ranges from 0.5 to 50 mg / ml. There is a group of people in whom bile is devoid of protein, while in others, on the contrary, bile is enriched in protein. One way or another, but protein is the third of the main organic components of bile. On average, a person receives about 10 g of it per day and it can be divided into 10-25 protein fractions. They, for the most part, are serum proteins: these are IgA and haptoglobin. Albumin and the rest is formed in the hepatocyte and epithelial cells of the bile ducts. Bile contains IgA (42%), IgG (68%), IgM (10%), but only IgG by its origin is completely serum protein. The rest are partially synthesized by immunocompetent cells of the portal vein, bile ducts, and the liver itself. A day in humans, about 28 mg of IgA from the blood serum into the bile enters the bile, much more, about 77 mg, are of local origin. Monomeric IgA comes almost entirely from serum. The secretory component - glycoprotein is a specific protein that ensures the transfer of polymeric IgA, IgM through the epithelium in such a way that a complex is formed in the secretory component and immunoglobulin, and by transcytosis transfers the protein through the canalicular membrane of the hepatocyte. In humans, the source of the secretory component of bile is the epithelial cells of the bile ducts.
Bile proteins are represented by enzymes of plasma membranes and lysosomes and even pancreatic amylase. Of these, 5-nucleotidase, alkaline phosphatase, alkaline phosphodiesterase, L-leucyl-b-naphthylaminase, Mg -ATPase, b-glucuronidase, galactosidase, N-acetyl-b-glucosaminase can be indicated. Bile proteins perform one of the important functions, being a compound capable of regulating the secretion of that part of bile that does not depend on bile acids due to its osmotic properties (albumin). They catalyze in bile the conversion of water-soluble bilirubin - diglucuronide into a water-insoluble form of unconjugated bilirubin, thereby promoting the formation of pigment stones. Apoproteins A-I and A-II slow down or even prevent the formation of cholesterol nuclei and cholesterol crystals. Apo-B in human bile plays an important role in the transport of cholesterol.
It is known that the intensity of some metabolic reactions and, what is important, the synthesis of acid-dependent and acid-independent bile fractions depend on protein biosynthesis in liver cells. It is assumed that one of the probable causes of the development of intrahepatic cholestasis is a violation of protein biosynthesis in hepatocytes, which, in medical practice, can be caused by the use of antibiotics. On the plasma membrane of the hepatocyte, receptors for vasopressin, glucagon, insulin, norepinephrine are installed.
Bile secretion. The intralobular and interlobular bile ducts merge, merging to the hepatic ducts (Fig. 13). Here, outside the liver, there is one of the bile duct sphincters - the Mirizzi sphincter. The common bile duct pierces the wall of the duodenum, ending in a complex formation - a large duodenal papilla (Fateri papilla), which has a common cistern for pancreatic secretion and bile. In the large duodenal papilla, three sphincters are distinguished: the duct itself (Aschoff), the sphincter of the Boyden's nipple (Boyden) and the sphincter of the pancreatic duct, all united under the name of the sphincter of Oddi (Oddi).
The cystic duct connects the gallbladder to the hepatic duct. The gallbladder cavity is a reservoir of hepatic bile; its wall has several layers of smooth muscles and is capable of contraction. In it there is an intensive process of water absorption and mucin secretion into bile as part of the secretion of mucous glands. The concentration function of the gallbladder is carried out in the parietal layer of mucus. Due to this, more concentrated bile flows around the walls, sinks to the bottom of the bladder, while the nucleus in the center contains less concentrated bile. The filling of the gallbladder after its emptying in response to food stimulation and the achievement of relative homogeneity of its contents occurs no faster than after 120-180 minutes.
Even outside digestion, due to rhythmic fluctuations in the tone of the sphincters of the large duodenal nipple, changes in intracavitary pressure in the duodenum and the presence of a certain tone of the gallbladder, hepatic bile can enter the duodenum in small quantities. It is known that hepatic bile, even during digestion, for a short moment manages to reach the neck of the gallbladder and, spreading along its walls, changes the concentration of bile in the bladder.
The gallbladder plays a reservoir role not only between digestion, but also has a reservoir function during digestion.
Regulation of the motor activity of the end section of the common bile duct is provided by the following factors:
- By pressure in the common bile duct. With increasing pressure, the amount of bile passing through the duct increases. The sphincter opening phase is lengthened due to its closing phase.
- Pressure in the duodenum. The rise in intracavitary pressure in the duodenum causes spasm of the sphincter of Oddi. A decrease in gut pressure, caused, for example, by aspiration through a duodenal tube, increases the amount of bile flowing through the sphincter.
- Duodenal peristalsis. Under normal conditions, duodenal motility does not affect the flow of bile through the sphincter. With upward movements, spasm of the sphincter of Oddi occurs.
- Contents of the duodenum. If the intestine is free and does not contain chyme, the rhythmic activity of the sphincter is insignificant, and only a small amount of bile passes through it. The release of food from the stomach into the intestine causes a rapid change in the activity of the sphincter: the first reaction is a spasm of the sphincter of Oddi, probably caused by a rise in pressure in the intestine. This spasm does not depend on the type of food, its duration is 4-10 seconds, sometimes up to 30 minutes. An increase in the duration of this spasm is clearly pathological. This reaction is most severe after the infusion of hydrochloric acid into the duodenum. After a temporary spasm, the sphincter reopens, due to a decrease in its tone, caused largely by the type of food. Fat, olive oil, magnesium sulfate have the most effective effect on the sphincter. Carbohydrates have the least impact. The decrease in tone is probably due to the effect of chemicals on the mucous membrane of the duodenum, a local reflex and is not due to the effect of cholecystokinin-pancreazimin on the contraction of the gallbladder.
Under experimental conditions, the coordination of the motor activity of the stomach, gallbladder and sphincter apparatus of the biliary system has been proved. Electrophysiologically, it was established that the appearance of peak potentials (it is believed that they cause contractions) on the electrograms of the duodenum, gallbladder, Lutkens sphincter is synchronous with the appearance of peak potentials on the electrogram of the stomach. The electrical activity of the sphincter of Lutkens and the gallbladder has a peculiar cycle, where the increase in fast (peak potentials) activity occurs after three cycles to the fourth, synchronously with the peristalsis of the stomach. The rises and falls of intracavitary pressure in the gallbladder also alternate. In the interval between the periodic occurrence of peak potentials of the stomach, there are no peak potentials of the duodenum. A few seconds before the contraction of the antrum of the stomach, the initial part of the duodenum relaxes. This corresponds to the maximum intracavitary pressure of the gallbladder and the beginning of relaxation of its walls after the release of a portion of bile into the intestine. Almost simultaneously with the contraction of the antrum of the stomach, potentials arise on the muscles of the duodenum. At the same time, a maximum of the amplitude of the intracavitary pressure of the gallbladder is observed, which is explained by the closure of its sphincters and the cessation of the release of bile into the intestine.
Functional connections between the stomach, duodenum and biliary apparatus are not limited only to the relationship in the motor-evacuation activity of these organs. They can also be traced in resting conditions.
The role of bile in digestion. Bile, entering the duodenum, mixes with the chyme that leaves the stomach when the pH of the intestinal contents reaches an optimal level for the activity of pancreatic and intestinal enzymes. It promotes the hydrolysis of proteins, carbohydrates, and emulsifies fats.
Hepatic cells produce up to 1 liter of bile per day, which enters the intestines. Hepatic bile is a yellow liquid, gallbladder bile is more viscous, dark brown in color with a greenish tinge. Bile is formed continuously, and its entry into the intestine is associated with food intake. Bile consists of water, bile acids (glycocholic, taurocholic) and bile pigments (bilirubin, biliverdin), cholesterol, lecithin, mucin and inorganic compounds (phosphorus, potassium and calcium salts, etc.). The importance of bile in digestion is enormous. First of all, bile, irritating the nerve receptors of the mucous membrane, causes peristalsis, keeps fat in an emulsified state, which increases the field of influence of the lipase enzyme. Under the influence of bile, the activity of lipase and proteolytic enzymes increases. Bile neutralizes hydrochloric acid coming from the stomach, thereby maintaining the activity of trypsin, and inhibits the action of pepsin in gastric juice. Bile also has bactericidal properties.
The biliary system of the liver includes bile capillaries, septal and interlobular bile ducts, right and left hepatic, common hepatic, cystic, common bile ducts and gallbladder.
Bile capillaries have a diameter of 1-2 microns, their lumens are limited by hepatic cells (Fig. 269). Thus, the hepatic cell with one plane is directed towards the blood capillary, and with the other it limits the bile capillary. Bile capillaries are located in the beams at a depth of 2/3 of the radius of the lobule. From the bile capillaries, bile enters the periphery of the lobule into the surrounding septal bile ducts, which merge into the interlobular bile ducts (ductuli interlobulares). They connect into the right (1 cm long) and left (2 cm long) hepatic ducts (ductuli hepatici dexter et sinister), and the latter merge into a common hepatic duct (2 - 3 cm long) (ductus hepaticus communis) (Fig. 270) ... It leaves the gates of the liver and connects to the cystic duct (ductus cysticus) 3-4 cm long. From the junction of the common hepatic and cystic ducts, the common bile duct (ductus choledochus) 5-8 cm long begins and flows into the duodenum. At its mouth there is a sphincter that regulates the flow of bile from the liver and gallbladder.
269. Diagram of the structure of the bile capillaries.
1 - hepatic cell; 2 - bile capillaries; 3 - sinusoids; 4 - interlobular bile duct; 5 - interlobular vein; 6 - interlobular artery.
270. Gallbladder and opened bile ducts (according to RD Sinelnikov).
1 - ductus cysticus;
2 - ductus hepaticus communis;
3 - ductus choledochus;
4 - ductus pancreaticus;
5 ampulla hepatopancreatica;
6 - duodenum;
7 - fundus vesicae fellae;
8 - plicae tunicae mucosae vesicae fellae;
9 - plica spiralis;
10 - collum vesisae fellae.
All ducts are identical in structure. They are lined with cubic epithelium, and large ones with protocylindrical epithelium. In large ducts, the connective tissue layer is also much better expressed. Muscular elements are practically absent in the bile ducts, only in the cystic and common bile ducts there are sphincters.
The gallbladder (vesica fellea) has the shape of an elongated bag with a volume of 40-60 ml. In the gallbladder, bile is concentrated (6-10 times) due to the absorption of water. The gallbladder is located in front of the right longitudinal groove of the liver. Its wall consists of mucous, muscular and connective tissue membranes. The part of the wall facing the abdominal cavity is covered by the peritoneum. In the bubble, the bottom, body and neck are distinguished. The neck of the bladder faces the gate of the liver and, together with the cystic duct, is located in the lig. hepatoduodenale.
Topography of the bladder and common bile duct... The bottom of the gallbladder is in contact with the parietal peritoneum, projecting in the corner formed by the costal arch and the outer edge of the rectus abdominis muscle or at the intersection with the costal arch of the line connecting the apex of the axillary fossa with the umbilicus. The bladder is in contact with the transverse colon, the pyloric part of the stomach and the upper part of the duodenum.
The common bile duct lies in the lateral part of the lig. hepatoduodenale, where it can be easily palpated on a corpse or during surgery. Then the duct passes behind the upper part of the duodenum, located to the right of the portal vein or 3-4 cm from the pyloric sphincter, penetrating into the thickness of the pancreatic head; its end part pierces the inner wall of the descending part of the duodenum. In this part of the intestinal wall, the sphincter of the common bile duct (m. Sphincter ductus choledochi) is formed.
Bile secretion mechanism... Since bile is constantly produced in the liver, in the period between digestion, the sphincter of the common bile duct is reduced and bile enters the gallbladder, where it is concentrated by absorbing water. During the period of digestion, the wall of the gallbladder contracts and the sphincter of the common bile duct relaxes. The concentrated bile of the bladder mixes with the liquid hepatic bile and flows out into the intestines.
Biliary system- the apparatus of the digestive system, designed to remove into the intestine a physiologically important product produced in the liver - bile, which is involved in the digestion and absorption of fats and fat-soluble vitamins, in the suppression of putrefactive microflora in the intestine. Only in the presence of bile fats and fat-soluble vitamins (A, E, D, K) are broken down and become capable of being absorbed by the intestinal walls and assimilated by the body. Some harmful substances that a person receives from food and drugs, the liver, along with bile, secretes into the intestines for their subsequent removal from the body. The release of bile into the lumen of the duodenum in time should be consistent with food intake. In case of untimely and insufficient secretion of bile, fats remain undigested and are processed by bacteria - inhabitants of the gastrointestinal tract. This leads to the appearance of unpleasant sensations and pain in the abdomen, increased gas production, stool disorders, as well as a deficiency of fat-soluble vitamins: vitamin A (due to the lack of which night blindness develops), vitamin D (its deficiency leads to brittle bones), vitamin K (it the deficiency increases the possibility of bleeding). An important function of bile is to remove cholesterol from the body.
From the liver cells to the duodenum, bile passes through the bile duct system, accumulating in the gallbladder. Violations of contractions of the gallbladder and ducts worsen the activity of the entire biliary system and are aggravated by inflammatory processes, the formation of gallstones. One of the main reasons for the formation of stones in the biliary tract is metabolic disorders, in particular, cholesterol metabolism.
Interestingly, disturbances in the biliary system are not always detected in a timely manner., however, there is a characteristic complex of symptoms that unequivocally indicates deviations:
Pain in the epigastric region and right hypochondrium... As a rule, they have a clear connection with the intake of fatty and fried foods, smoked meats (abdominal pain that occurs on an empty stomach is not typical for diseases of the biliary system).
In the case of gallstone disease, pain can be triggered by shaking, driving, or sudden movements that move stones. In such cases, attacks of biliary colic develop - intense spastic pain. The local application of heat and the introduction of antispasmodics help to relieve spasms.
For an attack of biliary colic characterized by the appearance of "reflected pain" in the right half of the chest, right shoulder, right scapula. Also, in diseases of the biliary system, symptoms of bloating, excess gas, nausea, and bitterness in the mouth are frequent.
To prevent the development of gallstone disease, it is very important to ensure the coordinated work of all organs of the biliary system. This is what was created for
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