Gallbladder and bile

Gallbladder

The gallbladder is a hollow, pear-like-shaped (piriform) organ that lies on the cystic plate (gallbladder bed) under the liver segments IVB and V. The cystic plate is a fibroareolar tissue that attaches the superior surface of the gallbladder to the liver.

Anatomy

  • Location
    • Intraperitoneal organ
  • Size and volume
    • Length: 7–10 cm
    • Width: 2.5 cm (at its widest point)
    • Volume: 30–35 mL under normal conditions
      • Can hold up to 300 mL if the cystic duct is obstructed
  • Composition/structure
    • Fundus
    • Body
    • Infundibulum
      • Narrow portion of the body that is continuous with the neck of the gallbladder
    • Neck

Function

  • Storage of bile
    • Bile drains from the liver via small bile ducts.
    • Cholecystokinin (CCK) stimulates the gallbladder to contract, which then releases bile through the cystic duct, into the second part of the duodenum.
  • Concentration of bile
    • By absorption of electrolytes and water

Vasculature

Innervation

Cholecystitis causes referred pain to the right shoulder region because the phrenic nerve originates from spinal nerves C3–C5, which also provide somatic sensation to the shoulder area.

References:[1]

Biliary tract

Anatomy

The portal triad consists of the hepatic artery, portal vein, and common bile duct.

Bile

Composition

Bile is a secretion produced by the liver and stored in the gallbladder that aids in digestion, neutralization of gastric acid, fat absorption, and excretion of bilirubin and cholesterol.

A deficiency of bile acids can result in fat malabsorption and cholesterol stones in the gallbladder.

Function

Enterohepatic circulation

  • Substances metabolized in the liver are excreted into the bile.
    • Bile salts (95% of bile acids are reabsorbed back into the liver to be recycled)
      • Pass into the intestinal lumen
      • Reabsorbed in the intestinal mucosa (primarily the proximal and distal ileum)
      • Return to the liver via portal circulation
    • Bilirubin
      • 80% is excreted in feces as stercobilin.
      • 20% enters enterohepatic circulation.
        • 90% is recycled in the liver.
        • 10% is excreted by the kidney.

Gallstones

References:[2][3]

Embryology

  • Derived from endoderm
  • Starts to develop during the 4th week of embryonic development
  • Formed from the hepatic diverticulum (hepatic bud)
    • The bile duct arises from the hepatic diverticulum, which narrows and connects with the midgut.
    • The gallbladder and cystic duct form from a ventral outgrowth of the bile duct.

Microscopic anatomy

Layers of the gallbladder wall:

References:[2]

Clinical significance

Disorders of the biliary tract

Disorders of the bile

  • 1. Kapoor VK. Gallbladder Anatomy. In: Gest TR. Gallbladder Anatomy. New York, NY: WebMD. https://emedicine.medscape.com/article/1900182-overview. Updated December 8, 2017. Accessed June 7, 2018.
  • 2. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences; 2015.
  • 3. Hall JE. Guyton and Hall Textbook of Medical Physiology. Philadelphia, PA: Elsevier; 2016.
  • Chung KW. Gross Anatomy. Baltimore, MD: Lippincott Williams & Wilkins; 2005.
  • Kaplan. USMLE Step 1 Anatomy Lecture Notes 2016. Kaplan Publishing; 2015.
  • Kaplan. USMLE Step 1 Lecture Notes 2016: Physiology. Kaplan Publishing; 2015.
  • Le T, Bhushan V,‎ Sochat M, Chavda Y, Zureick A. First Aid for the USMLE Step 1 2018. New York, NY: McGraw-Hill Medical; 2017.
last updated 09/06/2018
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