L_10_Functional_&_Applied_Anatomy_of_the_liver_Autosaved.pdf

Functional & Applied Anatomy of the Liver, Gall Bladder & Pancreas MUHAMMAD ALBAHADILI 2022-2023 objectives At the end of lecture we able to Locate the liver, pancreas or gallbladder in abdominal cavity Explain their relation to GIT Differentiate clinical pro...

Functional & Applied Anatomy of the Liver, Gall Bladder & Pancreas MUHAMMAD ALBAHADILI 2022-2023 objectives At the end of lecture we able to Locate the liver, pancreas or gallbladder in abdominal cavity Explain their relation to GIT Differentiate clinical problem related each organ Liver  Largest glandular organ, roughly triangular, lies mainly in the right hypochondrium & extends into the epigastrium & left Liver hypochondrium, covered by a fibrous capsule (Glisson capsule) what is the largest organ in the body? ❖Covered by peritoneum except a small area (bare area) on its posterior surface where its is in contact with the inferior vena cava ❖Protected by the rib cage; ❖Superior, lateral, anterior & posterior surface in contact with the diaphragm; ❖inferior (visceral) surface in contact with parts of the GI tract ❖Not palpable in normal position; lower edge palpable in deep inspiration ❖Visceral surface contains the porta hepatis – for structures entering & leaving the liver  Fixation of the liver in its position By ligaments By vascular connection to IVC Coronary ligament Triangular ligament Falciform ligament Ligamentum teres (hepatis) Lesser omentum Ligaments of the liver  Falciform ligament & round ligament falciform ligament(flap of ventral mesentery attaches the liver to the ant. abdominal wall); contains the obliterated left umbilical vein (ligamentum teres) ❖ Falciform ligament covers the liver & is reflected on the superior surface as the coronary ligament which fixes it to the diaphragm Triangular ligament: fixes the liver to the diaphragm Lesser omentum  Anatomical Liver Lobes ❖ Divided into right & left lobes by the falciform ligament anteriorly; ❖ By ligamentum venosum poseriorly ❖ The right lobe is further subdivided by the right sagittal fissure into three parts: the main right lobe & the caudate & quadrate lobes; the caudate lobe is bounded by the inferior vena cava & the ligamentum venosum (remnant of ductus venosus – bypass for placental oxygenated blood to IVC during development) ❖ The quadrate lobe bounded by the bed of the gallbladder & the round ligament FUNCTIONAL SUBDIVISION OF LIVER Functional & surgical divisions of the liver are based on the distribution of vascular & biliary elements Each part receives its own primary branch of the hepatic artery and hepatic portal vein and is drained by its own hepatic duct. The caudate lobe may in fact be considered a third liver; its vascularization is independent of the bifurcation of the portal triad (it receives vessels from both bundles) and is drained by one or two small hepatic veins, which enter directly into the IVC  The liver can be further subdivided into four divisions and then into eight surgically resectable hepatic segments, each served independently by a secondary or tertiary branch of the portal triad, respectively Segments of Liver: Except for the caudate lobe (segment I), the liver is divided into right and left livers based on the primary (1°) division of the portal triad into right and left branches, the plane between the right and the left livers being the main portal fissure in which the middle hepatic vein lies  On the visceral surface, this plane is demarcated by the right sagittal fissure. The plane is demarcated on the diaphragmatic surface by extrapolating an imaginary line (the Cantlie line) from the notch for the fundus of the gallbladder to the IVC The right and left livers are subdivided vertically into medial and lateral divisions by the right portal(no external mark) and umbilical fissures, in which the right and left hepatic veins lie Each of the four divisions receives a secondary (2°) branch of the portal triad A transverse hepatic plane at the level of the horizontal parts of the right and left branches of the portal triad subdivide three of the four divisions (all but the left medial division), creating six hepatic segments, each receiving tertiary branches of the triad.  Liver – Vascular & Biliary Elements The liver has a dual blood supply consisting of: Hepatic artery (20-30%), Hepatic Portal Vein (70-80%) drain of the intestine! Each of them gives 50% of liver oxygenation;.left or right hepatic artery ligation leads to a physiologically healthy liver.Rt. Hepatic A. may arise from sup. Mesenteric A.Lt. hepatic A. may arise from Lt. gastric A Blood & Bile Flow in the Liver ❖Arterial blood & portal venous blood mix together in the liver sinusoids. ❖Sinusoidal blood drains into central veins > hepatic veins > inferior vena cava; ❖Direction of flow determined by relatively high pressure of blood in the portal vein vis- à-vis central vein. Blood from the liver is drained by Hepatic veins > Inferior vena cava  Liver – Vascular & Biliary Elements ❖ Right branches of the portal vein & hepatic artery distribute to the right lobe of the liver (5-8 segments) ❖ Left branches distribute to the caudate, quadrate & left lobe of the liver (2-4 segments) ❖ Right hepatic bile duct drains 5-8 segments ❖ Left hepatic duct drains 2-4 segments ❖ The third liver (caudate, 1) receives dual blood from the right & left portal triad ❖Bile secreted flows in the opposite direction to the blood flow. ❖Bile secretory system begins as bile canaliculi between adjacent hepatocytes; Bile canaliculi > bile ductules; ductules converge to form intra- & interlobular biliary ducts which converge to form right & left hepatic ducts. ❖Outside the liver, hepatic ducts form the common hepatic duct. ❖Common hepatic duct join cystic duct form common bile duct.  Nerve supply of liver The nerves of the liver are derived from the hepatic plexus the largest derivative of the celiac plexus. The hepatic plexus accompanies the branches of the hepatic artery and the hepatic portal vein to the liver. This plexus consists of sympathetic fibers (T6-T9) from the celiac plexus and parasympathetic fibers from the anterior and posterior vagal trunks. Nerve fibers accompany the vessels and biliary ducts of the portal triad. Other than vasoconstriction, their function is unclear. Lymphatic drainage of the liver superficial lymphatics in the sub-peritoneal fibrous capsule of the liver deep lymphatics in the connective tissue, Most lymph is formed in the perisinusoidal spaces (of Disse) and drains to the deep lymphatics in the surrounding intralobular portal triads. Superficial lymphatics from the anterior aspects of the diaphragmatic and visceral surfaces of the liver, and deep lymphatic vessels accompanying the portal triads, converge toward the porta hepatis.  The superficial lymphatics drain to the hepatic lymph nodes scattered along the hepatic vessels and ducts in the lesser omentum. Efferent lymphatic vessels from the hepatic nodes drain into celiac lymph nodes Superficial lymphatics from the posterior aspects of the diaphragmatic and visceral surfaces of the liver drain toward the bare area of the liver. Here they drain into phrenic  Liver – Microstructure Main unite of liver is lobule Hepatomegaly (enlarged liver) can be caused by: blood engorgement may be due to rise in central venous pressure (lack of valves in IVC & hepatic veins), congestive heart failure, bacterial & viral diseases (hepatitis) or parasite (hydatid cyst), tumours & metastatic carcinoma - 2° from organs drained by the hepatic portal system) percussion  Alcoholic Cirrhosis & Portal Hypertension Liver vulnerable to cellular damage & consequent scarring; replaced by fibrous tissue. Fibrous tissue surrounds intra-hepatic vessels & bile ducts > restriction of blood flow > ↑ pressure in HPV > portal hypertension Blood flow into systemic circulation via venous sites (porto-systemic anastomoses); vessels become varicosed and may rupture (haemorrhage). Complications portal hypertension: oesophageal varices: portal = left gastric veins & systemic = Oesophageal veins > via the azygos vein Ano-rectal varices (haemorrhoids): portal = superior rectal vein & systemic = middle and inferior rectal veins caput medusae: portal = paraumbilical vein & systemic = epigastric veins Retrocolic: portal = superior and inferior mesenteric veins tributaries & systemic = retroperitoneal vessels ;Rx TIPS = Shunt: Transjugular Intrahepatic Portosystemic Shunt gallbladder The gallbladder is a pear-shaped, hollow structure located under the liver and on the right side of the abdomen, about 7 to 10 cm long an average capacity of 30 to 50 ml located in a fossa on the inferior border of the liver, the body of the gall- bladder lies anterior to the superior part of the duodenum, and its neck and cystic duct are immediately superior to the duodenum Peritoneum surrounds the fundus of the gallbladder and binds its body and neck to the liver. The hepatic surface of the gallbladder attaches to the liver by connective tissue of the fibrous capsule of the liver.  Gallbladder ❖ Gall bladder has a fundus, body & neck > cystic duct Fundus: the wide blunt end that usually projects from the inferior border of the liver at the tip of the right 9th costal cartilage in the MCL Body: the main portion that contacts the visceral surface of the liver, transverse colon, and superior part of the duodenum. Neck: narrow, tapering end, directed toward the porta hepatis; The cystic duct (3–4 cm long) connects the neck of the gallbladder to the common hepatic duct The mucosa of the cystic duct spirals into the spiral fold (spiral valve) the spiral fold helps keep the cystic duct open.  bile ducts ❖ Right & left hepatic ducts leaving the porta hepatis to join to form the common hepatic duct (4 cm) ❖ Joined on the right by the cystic duct from the bile duct; which lies in the free border of the lesser omentum  Gall bladder & bile ducts ❖ Opens into the 2nd part of the duodenum with the main pancreatic duct through sphincter of Oddi  blood supply – cystic artery (br. Right hepatic art- RHA.); RHA also supplies part of the common bile duct Venous drainage fellows the artery  Gall bladder & bile ducts Lymphatic: The lymphatic vessels of the gall bladder (subserosal and submucosal) drain into the cystic lymph node of Lund (the sentinel lymph node), which lies in the fork created by the junction of the cystic and common hepatic ducts. Efferent vessels from this lymph node go to the hilum of the liver, and to the coeliac lymph nodes. The subserosal lymphatic vessels of the gall bladder also connect with the subcapsular lymph channels of the liver, and this accounts for the frequent spread of carcinoma of the gall bladder to the liver.  Nerve supply of Gall bladder & bile ducts ❖ Nerve supply to the gall bladder & cystic duct from the coeliac plexus sympathetic (sensory) visceral afferent pain fibres) ❖ and from the Vagus nerve parasympathetic (motor) ❖ Parasympathetic stimulation > contraction of gall bladder & relaxation of the sphincter of Oddi; these responses are also stimulated by the hormone (cholecystokinin (CCK) produced by the duodenum upon the arrival of food (fat) in the duodenum ❖ Somatic (afferent) to right phrenic n. ❖ Gall bladder stores, concentrates bile & secretion of mucus; biliary ducts convey bile to the duodenum; released intermittently ❖ Mucosa of the neck spirals into spiral fold – keeps the cystic duct open; allows the gall bladder to fill up when the distal end of the common bile duct is closed off by its sphincter at the lower end. Clinical condition: Gall stones Bile produce by the liver and excreted in bile canaliculi is within 500 to 1000 ml Composed of water, electrolytes, bile salts, protein, cholesterol and bile pigments Stone formed as a result of solids settling out of solution The major organic solutes are bile salts, bile pigments, phospholipid and cholesterol Causes of gallstone Too much absorption of water from of bile Too much absorption of bile acids from of bile Too much cholesterol in bile Too much bile pigment in bile Inflammation of epithelium of gallbladder  Gall stone Gallstones can be divided into three main types: cholesterol, pigment (brown/black) or mixed stones. Effects and complications of gallstones Biliary colic Acute cholecystitis Chronic cholecystitis Empyema of the gall bladder Mucocoele Perforation Biliary obstruction Acute cholangitis Acute pancreatitis Intestinal obstruction (gallstone ileus) ❖ Cholecystitis (inflammation of gall bladder) due to bile accumulation > pain in the epigastrium or the right hypochondrium; gall bladder derivative of the foregut (sympathetic innervation from T5 – T9 & pain fibres return to T7 – T9 segments of the spinal cord; pain felt along 7th – 9th intercostal spaces (from inf. angle of scapula to epigastrium) ❖Pain referred to the tip of the right shoulder (C3 - C5) ❖Cholecystectomy (removal of the gall bladder) presents surgical challenges because of variations in the anatomy & blood supply of the biliary system. Pancreas  Pancreas ▪ The name ‘pancreas’ is derived from the Greek ‘pan’ (all) and ‘kreas’ (flesh). For a long time, its glandular function was not understood, and it was thought to act as a cushion for the stomach. ▪ It’s a retroperitoneal organ ▪ Parts of the pancreas: ▪ Head ▪ Neck ▪ Body ▪ Tail ▪ Uncinate process Pancreas: anteriorly is the lesser sac  Pancreas: Anatomy The head lies within the curve of the duodenum, overlying the body of the second lumbar vertebra. The pancreatic head rests posteriorly on the IVC, right kidney hilum, to the right of the superior mesenteric vessels just inferior to the transpyloric plane. It firmly attaches to the medial aspect of the descending and horizontal parts of the duodenum. the bile duct lies in a groove on the posterosuperior surface of the head or is embedded in its substance  The neck of the pancreas is short (1.5–2 cm) and overlies the superior mesenteric vessels, which form a groove in its posterior aspect. The anterior surface of the neck, covered with peritoneum, is adjacent to the pylorus of the stomach. The SMV joins the splenic vein posterior to the neck to form the hepatic portal vein uncinated process of the pancreas Coming off the side of the pancreatic head and passing to the left and behind the superior mesenteric vein. The body of the pancreas continues from the neck and lies to the left of the superior mesenteric vessels, passing over the aorta and L2 vertebra, continuing just above the transpyloric plane posterior to the omental bursa. The anterior surface of the body of the pancreas is covered with peritoneum The posterior surface of the body is devoid of peritoneum and is in contact with the aorta, SMA, left suprarenal gland, left kidney, and renal vessels  The tail of the pancreas lies anterior to the left kidney, where it is closely related to the splenic hilum and the left colic flexure. The tail is relatively mobile and passes between the layers of the splenorenal ligament with the splenic vessels  Pancreas: blood supply superior mesenteric Pancreas: blood Gastroduodenal splenic artery supply anterior superior anterior inferior posterior superior posterior inferior Inferior pancratic Greater pancreatic Dorsal pancreatic To the tail pancreaticoduodenal pancreaticoduodenal Venous drainage of pancreas. LYMPHATIC DRAINAGE OF THE PANCREAS ▪ Diffuse and widespread ▪ The pancreatic lymphatic vessels follow the blood vessels ▪ Most vessels end in the pancreatic-splenic lymph nodes, which lie along the splenic artery. ▪ Some vessels end in the pyloric lymph nodes. Efferent vessels from these nodes drain to the superior mesenteric lymph nodes or to the celiac lymph nodes via the hepatic lymph nodes. ▪ Communicate with lymph nodes in transverse mesocolon and mesentery  Pancreas is: (mixed gland); exocrine secretions (acinar cells pancreatic juice) > duodenum via main & accessory ducts; endocrine secretions ( islets of Langarhans) > blood Main pancreatic duct together with the common bile duct form the (hepatopancreatic ampulla of Vater) and open into the 2nd part of the duodenum at the major duodenal papilla  An accessory pancreatic duct drains the upper (superior) part of the head of the pancreas and opens in the duodenum at the minor duodenal papilla 2 cm anterosuperior to the major papilla The main duct is lined by columnar epithelium, which becomes cuboidal in the ductules. Acinar cells are clumped around a central lumen, which communicates with the duct system. Clusters of endocrine cells, known as islets of Langerhans, are distributed throughout the pancreas. Islets consist of different cell types: 75 per cent are B cells (producing insulin); 20 per cent are A cells (producing glucagon); and the remainder are D cells (producing somatostatin) and a small number of pancreatic polypeptide cells. Within an islet, the B cells form an inner core surrounded by the other cells. Capillaries draining the islet cells drain into the portal vein, forming a pancreatic portal system. Pancreas - Microstructure  Pseudocyst of pancreas formed when disruption of the main pancreatic duct or its branches, either from inflammation or direct injury, causes extravasation of pancreatic enzymes into the parenchyma and eventually forms a distinct collection. Pseudocysts arise as a complication of pancreatitis. It appears that alcohol-related pancreatitis is the major cause of pancreatic pseudocyst The remaining causative factors are biliary stones, trauma, or idiopathic. A pseudocyst is formed following an episode of acute pancreatitis, often within 4 to 6 weeks of that episode, with a well-defined wall lined by granulation or fibrous tissue. They are filled with amylase rich fluid. About one-third of pseudocysts are located near the head of the gland, and the remaining two-thirds occur in the tail.  Pancreas: clinical correlates Impaction (gallstone) of the hepatopancreatic ampulla) > secretions from the gall bladder & pancreas blocked - interruption of pancreatic juice flow > pancreatitis - interruption of bile flow > ‘post-hepatic (obstructive) jaundice’ Pancreatic cancer (head) > extrahepatic obstruction of biliary ducts > enlargement of gall bladder > obstructive jaundice