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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APPLIED ANATOMY AND HISTOLOGY
OF LIVER, HEPATIC CIRCULATION
AND FACTORS AFFECTING HEPATIC
University College of Medical Science & GTB Hospital, Delhi
Parasympathetic fibers - Rt&Ltvagus
IVC and Hepatic nodes
HISTOLOGY OF THE LIVER
Hepatocytes - polyhedral , with a central spherical nucleus.
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
-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
Functional unit of the liver
Metabolism of proteins, carbohydrates, lipids
Metabolism of heme, bile
Synthesis of coagulants-2,7,9,10,protein S,C
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.
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.
Phase 3 Elimination
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.
HEPATIC ARTERIOLE+PORTAL VENULE
SPACE OF DISSE
CENTRAL VEIN(TERMINALHEPATIC VENULE)
MAIN HEPATIC VEIN
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
Vagus ,Phrenic nerve
Hepatic a.— vasoconstriction followed by vasodilation
Portal v--- vasoconstriction
constricts splanchic arterial bed
decreases portal venous resistance
FACTORS INCREASING HEPATIC BLOOD FLOW
FACTORS DECREASING HEPATIC BLOOD FLOW
H2 BLOCKERS CIMETIDINE,RANITIDINE,VASOPRESSIN
ANESTHETICS-VOLATILE AND INTRAVENOUS
Ventilation- IPPV, PEEP
Surgery – direct vascular compression, local reflexes, reflex sympathetic stimulation
PHARMACOLOGY AND PHYSIOLOGY IN ANAESTHETIC PRACTICE, 4TH EDITION