Presentation on theme: "University College of Medical Science & GTB Hospital, Delhi"— Presentation transcript:
1University College of Medical Science & GTB Hospital, Delhi APPLIED ANATOMY AND HISTOLOGYOF LIVER, HEPATIC CIRCULATIONAND FACTORS AFFECTING HEPATICBLOOD FLOWdR kavitha lakshmanUniversity College of Medical Science & GTB Hospital, Delhi
2ANATOMY OF THE LIVER Largest gland, largest reticuloendothelial organ Weighs around 1.2 to 1.6 KgOccupies the right upper quadrant of the abdomenInvested in peritoneum except – gallbladder bed, IVC, bare area of liverLigaments- duplication of peritoneum over the liverInvolved in a wide variety of metabolic functions recq for homeostasis, nutrition-plethora of biochemical reactions
4DIVISIONS OF THE LIVERFalciform ligament-oversimplified,anatomically incorrectCantlie's line- a plane running from the gall-bladder to the left side of the IVCCouinad’s segments- 8 functional segments, each supplied by a pedicleBismuth’s classification- 4 sectors separated by scissurae containing the three main Hepatic vein
8NERVE SUPPLY AND LYMPHATIC Sympathetic nerve fibers T6–T11Parasympathetic fibers Rt&Lt vagusRt Phenic.NSuperficial lymphatics:Surface of organ and terminate in Caval ,Hepatic,Celiac lymph nodesDeep lymphatics:IVC and Hepatic nodes
10HEPATOCYTESthe plasma membrane of the hepatocyte is organized into three specific domains. the sinusoidal membrane is exposed to the space of disse and has multiple microvilli that provide a surface specialized in the active transport of substances between the blood and hepatocyte. the lateral domain exists between neighboring hepatocytes and contains gap junctions that provide for intercellular communication. the canalicular membrane is a tube containing microvilli formed by two apposing hepatocytes. these bile canaliculi are sealed by zonulae occludentes (tight junctions), which prevent escape of bile.
11HEPATOCYTESHepatocytes - polyhedral , with a central spherical nucleus. Single-cell-layer plates Lined on either sides by sinusoids. Every hepatocyte has contact with adjacent hepatocytes, the biliary space (bile canaliculus), and the sinusoidal space, allowing its broad range of functions
14SINUSOIDS Sinusoids are blood filled spaces 10um in diameter Hepatic and Portal blood mixes hereEndothelial cells-lack intercellular junctions-Absence of basement membrane-Contain multiple and large fenestrations.Maximal contact of hepatocyte membrane(space of Disse) and blood in the sinusoidal space.Permits free bidirectional movement of solutes
15KUFFER CELLS Resident macrophages line sinusoids Partly derived from bone marrow monocytesClearance of gut derived toxinsEngulf debris and dead rbcsSecrete cytokines IL-1,IL-6,TNF alfaExpress class II MHC- antigen presentation
17ITO CELLS Found in the space of Disse. They have dendritic processes which are in contact with hepatocyte microvilli and endothelial cells.Vitamin A storageSynthesis of extracellular collagen.Play a central role in the development and progression of hepatic fibrosis
18HEPATIC LOBULE50, lobulesFunctional unit of the liver
21FUNCTIONS OF HEPATOCYTES Metabolism of proteins, carbohydrates, lipids Metabolism of heme, bile Synthesis of coagulants-2,7,9,10,protein S,C Drug metabolism Immune defense
22DRUG METABOLISMPhase 1 Metabolism e.g. oxidations, reductions, hydrolysis convert drugs to more polar compounds The products of phase 1 metabolism are -Readily excreted in bile or urine than their precursors are. -These products may also be substrates for phase 2 conjugations.
23Phase 2 metabolism Conjugate xenobiotics or their metabolites with endogenous hydrophilic molecules such as glucuronic acid, acetate, sulfates, amino acids, and glutathione, glucuronic acid etc When compared with their precursors, conjugated xenobiotics are usually less efficacious, less toxic, more hydrophilic, and more readily excreted in bile or urine.
24Phase 3 Elimination Involve specific molecular transporters—known as ATP-binding cassette (ABC) transport proteins—that facilitate the excretion of xenobiotics and endogenous compounds.These proteins use ATP hydrolysis to drive molecular transport.Major ABC transport proteins include cystic fibrosis transmembrane conductance regulator (CFTR), canalicular copper transporters, and multidrug resistance protein (MDR).
25dysfunction of ABC transport proteins can disrupt the flow of bile, impair excretion of xenobiotics and endogenous compounds, and induce cholestatic liver injury.
27Blood supply of liverThe liver is at the hub of the splanchnic circulation. Receives 25% of the total cardiac output via a dual vascular supply. Arterial blood is supplied via the hepatic artery—a branch of the common hepatic artery that has its origin at the celiac trunk of the abdominal aorta On the other hand, the portal vein has as its tributaries the superior mesenteric and splenic veins, which carry the entire venous drainage of the preportal splanchnic beds.
30HA+PVHEPATIC ARTERIOLE+PORTAL VENULESINUSOIDS(FENESTERATED ENOTHELIUM)HEPATOCYTESSINUSOIDSSPACE OF DISSECENTRAL VEIN(TERMINALHEPATIC VENULE)LOBULEMAIN HEPATIC VEINIVC
31PORTAL VEIN Begins and ends in a network of capillaries lack of valves - accommodate high flow at low pressure because of the low resistance75% of hepatic blood flowPostcapillary and largely deoxygenatedlarge-volume flow rate provides 50% to 70% of the liver's oxygenation.
32Numerous connections exists between the portal venous system and the systemic venous system. Provide collateral supply under conditions of high portal venous pressure 1. Submucosal veins of the proximal stomach and distal esophagus, which receive portal flow from the short gastric veins and the left gastric vein 2.Umbilical and abdominal wall veins, which recanalize from flow through the umbilical vein in the ligamentum teres 3.Superior hemorrhoidal plexus, which receives portal flow from inferior mesenteric vein tributaries
38METABOLIC CONTROLLow pH and oxygen tension portal blood increases hepatic blood flowPostprandial hyperosmolarity increases both hepatic and portal blood flow
39NEURAL CONTROL Post ganglionic sym. T6-T11 Vagus ,Phrenic nerve Sympathoadrenal stimulation (hypercarbia,hypoxia,pain) vasoconstriction—decrease in hbfWith in sec, splanchnic stimulation autotransfuse ml (80% total hepatic blood vol)into central circulation in healthy euvolemic individuals
40HUMORAL CONTROL EPINEPHRINE Hepatic a.— vasoconstriction followed by vasodilationPortal v vasoconstrictionDOPAMINE vasodilationGlucagon vasodilationAngitention II -vasoconstrictionVasopressin -constricts splanchic arterial beddecreases portal venous resistance
42EFFECT OF ANAESTHESIA ON HEPATIC BLOOD FLOW Hepatic blood flow usually decreases during regional and general anesthesiaAll volatile anesthetic agents reduce portal hepatic blood flow- halothaneIndution agents- ketamine increases flowGA-decrease in map, co, reflex sympathetic stimulationSpinal and epidural anesthesia decrease hepatic blood flow primarily by lowering arterial blood pressure.
43Ventilation- IPPV, PEEP Surgery – direct vascular compression, local reflexes, reflex sympathetic stimulation
44REFERENCESPHILIP SM, SIMON G, HEPATIC PHYSIOLOGY AND PATHOLOGY,MILLERS 7TH EDITION,BRAIN S, DAVID ROCCAFORTE. HEPATIC ANATOMY, FUNCTION AND PHYSIOLOGY. CLINICAL ANAESTHESIA,6TH EDITION,EDWARD MORGAN . HEPATIC PHYSIOLOGY AND ANAESTHESIA.CLINICAL ANAESTHESIOLOGY, 4TH EDITIONINTERNATIONAL PRACTICE OF ANAESTHESIA, PRYS ROBERTSMICHAEL A, YUMNG F, ANATOMY AND PHYSIOLOGY OF THE LIVER,SABISTON TEXT BOOK OF SURGERY, 18TH EDITIONNEIL R B,ANATOMY OF THE LIVER .GRAY’S ANATOMY 39TH EDITIONHEPATIC PHYSIOLOGY,GANONG 22ND EDITIONSTOELTING R, HILLIER S, LIVER AND GASTROINTESTINAL TRACTPHARMACOLOGY AND PHYSIOLOGY IN ANAESTHETIC PRACTICE, 4TH EDITION