Dr kavitha lakshman
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APPLIED ANATOMY AND HISTOLOGY OF LIVER , HEPATIC CIRCULATION AND FACTORS AFFECTING HEPATIC BLOOD FLOW. dR kavitha lakshman. University College of Medical Science & GTB Hospital, Delhi. ANATOMY OF THE LIVER. Largest gland, largest reticuloendothelial organ

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Dr kavitha lakshman

APPLIED ANATOMY AND HISTOLOGY

OF LIVER, HEPATIC CIRCULATION

AND FACTORS AFFECTING HEPATIC

BLOOD FLOW

dRkavithalakshman

University College of Medical Science & GTB Hospital, Delhi


Anatomy of the liver

ANATOMY OF THE LIVER

  • Largest gland, largest reticuloendothelial organ

  • Weighs around 1.2 to 1.6 Kg

  • Occupies the right upper quadrant of the abdomen

  • Invested in peritoneum except – gallbladder bed, IVC, bare area of liver

  • Ligaments- duplication of peritoneum over the liver


External features of liver

EXTERNAL FEATURESOF LIVER


Divisions of the liver

DIVISIONS OF THE LIVER

  • Falciform ligament-oversimplified,anatomically incorrect

  • Cantlie's line- a plane running from the gall-bladder to the left side of the IVC

  • Couinad’s segments- 8 functional segments, each supplied by a pedicle

  • Bismuth’s classification- 4 sectors separated by scissurae containing the three main Hepatic vein


Segments of liver

SEGMENTS OF LIVER


Sectors of liver

SECTORS OF LIVER


Bile duct

BILE DUCT


Nerve supply and lymphatic

NERVE SUPPLY AND LYMPHATIC

  • Sympathetic nerve fibers - T6–T11

    Parasympathetic fibers - Rt&Ltvagus

    RtPhenic.N

  • Superficial lymphatics:Surface of organ and terminate in Caval ,Hepatic,Celiac lymph nodes

  • Deep lymphatics:

    IVC and Hepatic nodes


Histology of the liver

HISTOLOGY OF THE LIVER


Hepatocytes

HEPATOCYTES


Hepatocytes1

HEPATOCYTES

Hepatocytes - 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


Sinusoids

SINUSOIDS

  • Sinusoids are blood filled spaces

  • 10um in diameter

  • Hepatic and Portal blood mixes here

  • Endothelial 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


Kuffer cells

KUFFER CELLS

  • Resident macrophages line sinusoids

  • Partly derived from bone marrow monocytes

  • Clearance of gut derived toxins

  • Engulf debris and dead rbcs

  • Secrete cytokines IL-1,IL-6,TNF alfa

  • Express class II MHC- antigen presentation


Kuffer cell

KUFFER CELL


Ito cells

ITO CELLS

  • Found in the space of Disse.

  • They have dendritic processes which are in contact with hepatocytemicrovilli and endothelial cells.

  • Vitamin A storage

  • Synthesis of extracellular collagen.

  • Play a central role in the development and progression of hepatic fibrosis


Hepatic lobule

HEPATIC LOBULE

50,000-100000 lobules

Functional unit of the liver


Portal triad

PORTAL TRIAD


Hepatic architecture

HEPATIC ARCHITECTURE


Functions of hepatocytes

FUNCTIONS 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


Drug metabolism

DRUG METABOLISM

Phase 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.


Dr kavitha lakshman

Phase 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.


Dr kavitha lakshman

Phase 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).


Dr kavitha lakshman

  • dysfunction of ABC transport proteins can disrupt the flow of bile, impair excretion of xenobiotics and endogenous compounds, and induce cholestatic liver injury.


Blood supply of liver

Blood supply of liver

The 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 preportalsplanchnic beds.


Dr kavitha lakshman

HA+PV

HEPATIC ARTERIOLE+PORTAL VENULE

SINUSOIDS(FENESTERATED ENOTHELIUM)

HEPATOCYTES

SINUSOIDS

SPACE OF DISSE

CENTRAL VEIN(TERMINALHEPATIC VENULE)

LOBULE

MAIN HEPATIC VEIN

IVC


Portal vein

PORTAL VEIN

  • Begins and ends in a network of capillaries

  • lack of valves - accommodate high flow at low pressure because of the low resistance

  • 75% of hepatic blood flow

  • Postcapillary and largely deoxygenated

  • large-volume flow rate provides 50% to 70% of the liver's oxygenation.


Dr kavitha lakshman

  • Numerous 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 ligamentumteres

    3.Superior hemorrhoidal plexus, which receives portal flow from inferior mesenteric vein tributaries


Factors affecting the hepatic blood flow

FACTORS AFFECTING THE HEPATIC BLOOD FLOW

INTRINSIC REGULATION

  • HEPATIC ARTERIAL BUFFER RESPONSE

  • METABOLIC CONTROL

  • PRESSURE FLOW AUTO REGULATION

    EXTRINSIC REGULATION

  • NEURAL CONTROL

  • HUMORAL CONTROL


Hepatic arterial buffer response

HEPATIC ARTERIAL BUFFER RESPONSE

  • Change in portal venous flow-reciprocal change in hepatic arterial flow

  • Adenosine in periportal region

  • Can double hepatic arterial flow

  • Disrupted in endotoxemia , splancnichypoperfusion, portal inflow falls by >50%


Pressure flow autoregulation

PRESSURE FLOW AUTOREGULATION

  • Myogenic response –vascular smooth muscle

  • Transmural pressure-myogenic tone-vessel caliber-dec blood flow

  • Hepatic artery-present

  • Fed state- active

  • Is of minimal significance intraoperatively


Metabolic control

METABOLIC CONTROL

  • Low pH and oxygen tension portal blood increases hepatic blood flow

  • Postprandial hyperosmolarity increases both hepatic and portal blood flow


Neural control

NEURAL CONTROL

  • Post ganglionic sym. T6-T11

    Vagus ,Phrenic nerve

  • Sympathoadrenal stimulation (hypercarbia,hypoxia,pain) vasoconstriction—decrease in hbf

  • With in sec, splanchnic stimulation autotransfuse 400-500 ml (80% total hepatic blood vol)into central circulation in healthy euvolemic individuals


Humoral control

HUMORAL CONTROL

  • EPINEPHRINE

    Hepatic a.— vasoconstriction followed by vasodilation

    Portal v--- vasoconstriction

  • DOPAMINE -vasodilation

  • Glucagon -vasodilation

  • Angitention II -vasoconstriction

  • Vasopressin -

    constricts splanchic arterial bed

    decreases portal venous resistance


Dr kavitha lakshman

FACTORS INCREASING HEPATIC BLOOD FLOW

FACTORS DECREASING HEPATIC BLOOD FLOW

IPPV+PEEP

SURGERY

HYPOCAPNIA;HYPOXIA

UPRIGHT POSTURE

CIRRHOSIS

DRUGS

A-AGONIST

B-BLOCKERS

H2 BLOCKERS CIMETIDINE,RANITIDINE,VASOPRESSIN

ANESTHETICS-VOLATILE AND INTRAVENOUS

  • HYPERCAPNIA

  • AC.HEPATITIS -VIRAL,ALCOHOLIC

  • SUPINE POSTION

  • FOOD

  • DRUGS

    B-AGONIST

    PHENOBARBITONE


Effect of anaesthesia on hepatic blood flow

EFFECT OF ANAESTHESIA ON HEPATIC BLOOD FLOW

  • Hepatic blood flow usually decreasesduring regional and general anesthesia

  • All volatile anesthetic agents reduce portal hepatic blood flow- halothane

  • Indution agents- ketamine increases flow

  • GA-decrease in map, co, reflex sympathetic stimulation

  • Spinal and epidural anesthesia decrease hepatic blood flow primarily by lowering arterial blood pressure.


Dr kavitha lakshman

Ventilation- IPPV, PEEP

Surgery – direct vascular compression, local reflexes, reflex sympathetic stimulation


References

REFERENCES

  • PHILIP SM, SIMON G, HEPATIC PHYSIOLOGY AND PATHOLOGY,MILLERS 7TH EDITION,411-435

  • BRAIN S, DAVID ROCCAFORTE. HEPATIC ANATOMY, FUNCTION AND PHYSIOLOGY. CLINICAL ANAESTHESIA,6TH EDITION,1247-78

  • EDWARD MORGAN . HEPATIC PHYSIOLOGY AND ANAESTHESIA.CLINICAL ANAESTHESIOLOGY, 4TH EDITION

  • INTERNATIONAL PRACTICE OF ANAESTHESIA, PRYS ROBERTS

  • MICHAEL A, YUMNG F, ANATOMY AND PHYSIOLOGY OF THE LIVER,SABISTON TEXT BOOK OF SURGERY, 18TH EDITION

  • NEIL R B,ANATOMY OF THE LIVER .GRAY’S ANATOMY 39TH EDITION

  • HEPATIC PHYSIOLOGY,GANONG 22ND EDITION

  • STOELTING R, HILLIER S, LIVER AND GASTROINTESTINAL TRACT

    PHARMACOLOGY AND PHYSIOLOGY IN ANAESTHETIC PRACTICE, 4TH EDITION


Thank you

THANK YOU


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