Liver & intrahepatic bile ducts
General
Anatomy


Topic Completed: 1 April 2012

Minor changes: 3 August 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Anatomy[title] liver[title] "loattrfree full text"[sb]


Komal Arora, M.D.
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Cite this page: Arora K. Anatomy. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/livernormalanatomy.html. Accessed August 7th, 2020.
Definition / general
  • 1,200 - 1,600 g
  • Dual blood supply of portal vein (2/3) and hepatic artery (1/3) via porta hepatis (common hepatic bile duct exists in same region)
  • Blood exits liver via left and right hepatic veins to inferior vena cava
  • Divided into right and left lobes by Cantlie line projecting between gallbladder fossa and vena cava and defined by middle hepatic vein
  • Right lobe is divided into anterior and posterior segments by right hepatic vein
  • Left lobe is divided into medial and lateral segments by left hepatic vein
  • Intrahepatic biliary tree: classified into intrahepatic large bile ducts (grossly visible with fibrous ductal wall and peribiliary glands) and small bile ducts
  • Regional lymph nodes: hilar, hepatoduodenal ligament, caval
Embryology
  • Arises at embryonic junction (septum transversum): where ectoderm of amnion meets endoderm of yolk sac (externally) and where foregut meets midgut (internally); mesenchymal structure of transverse septum provides support so blood vessels and liver can form in underlying splanchnic mesoderm (UNSW Embryology: Gastrointestinal Tract - Liver Development [Accessed 23 October 2017])
  • Hepatic diverticulum buds from ventral foregut at end of third week, grows into primitive septum transversum
  • Liver forms from endodermal cells of diverticulum, termed hepatoblasts and mesenchyme
  • Blood supply primarily from umbilical vein; also portal vein and hepatic artery
  • Placenta clears wastes in bile and absorbs nutrients and umbilical vein blood bypasses liver via ductus venosus
  • All elements of the biliary tree are recognizable by week 5, although bile duct system not complete until after birth; derived from endoderm (large ducts) and embryonic ductal plate (smaller intrahepatic ducts, Dig Surg 2010;27:87)
  • Hematopoietic cells are present in embryonic / fetal liver but absent at term
Physiology
Bile:
  • Liver produces about 500 ml/day of bile
  • Promotes dietary fat absorption via detergent action of bile salts; eliminates waste products (bilirubin, excess cholesterol, xenobiotics) that are insufficiently water soluble to be excreted into urine

Bile acids:
  • Carboxylate steroid molecules, derived from cholesterol, that promote bile flow and secretion of phospholipid and cholesterol
  • Primary bile acids are cholic acid and chenodeoxycholic acid, secreted as taurine and glycine conjugates; two secondary ones (deoxycholic and lithocholic acid) are formed in the colon by bacterial action

Images hosted on other servers:

Bile acids



Bile acid circulation:
  • All bile acids are reabsorbed via sodium bile acid cotransporter in apical membrane of ileal enterocytes and transported back to liver
  • Enterohepatic circulation of bile acids maintains a large endogenous pool of bile acids for digestive and excretory purposes


Jaundice:
  • Also called icterus
  • Discoloration of skin and sclera due to disruption of bile formation by either retention of pigmented bilirubin or block in bilirubin secretion (cholestasis)

Bilirubin:
  • End product of heme degradation
  • 200 mg produced daily from old red blood cells broken down via monocyte phagocytic system in spleen, liver, marrow
  • Also from turnover of P450 cytochromes and premature destruction of marrow red blood cells (with ineffective erthyropoiesis)
  • Red blood cells are broken down and produce hemoglobin
  • Globin proteins are removed, leaving heme molecule
  • Heme is converted to biliverdin via heme oxygenase
  • Biliverdin is converted to bilirubin via biliverdin reductase
  • Bilirubin is bound to serum albumin since it is insoluble in blood at physiologic pH; the % unbound increases in severe hemolytic disease or if protein binding drugs displace bilirubin
  • Hepatocytes take in bilirubin at sinusoidal membrane, conjugate it with glucuronic acid using bilirubin uridine diphosphate glucuronosyltransferase (UGT) in endoplasmic reticulum, then bilirubin is excreted into bile
  • Bacteria have beta glucuronidases which deconjugate and degrade bilirubin to colorless urobilinogens, excreted in feces as stercobilin, a brown pigment that colors stools
  • 20% of urobilinogens are reabsorbed in ileum / colon, returned to liver, reexcreted into bile
  • Some urobilinogen is reabsorbed and excreted by the kidney, oxidized to urobilin - a pigment that gives amber color to urine
Accessory lobe
  • May appear clinically as hepatic mass
  • Anterior abdominal wall defects are frequently associated with accessory hepatic lobes
  • Can present with torsion (Surg Radiol Anat 2011;33:819)
Diagrams / tables

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Embryonic hepatic bud formation

Anterior and posterior views

Blood supply

Intrahepatic biliary tree

Clinical images

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Accessory lobe with its pedicle (arrow) and the adherent gallbladder (arrowheads)

Microscopic (histologic) images

Images contributed by Dr. Grigory Demyashkin, I. M. Sechenov First Moscow State Medical University (Russia):

6 - 8 week embryo:

Liver

Upper left: small intestine; bottom left: esophagus; center: stomach; top right: pancreas; right: liver

Liver, islets of hematopoiesis

Left, above: final kidney (metanephros); lower left: liver; center: gonad and kidney primary (mesonephros); right: symphysis

Videos

Development of foregut related to the peritoneum

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