Last updated: August 25, 2023

Summarytoggle arrow icon

The liver is a wedge-shaped organ that is located underneath the diaphragm in the right upper abdominal quadrant. It is covered by a capsule and connected to surrounding structures via ligaments. The porta hepatis structures are found in a fissure between two of the four liver lobes. The hepatic artery proper and the portal vein provide the liver with a dual blood supply. Microscopically, the liver is divided into lobules, each with a central vein and a portal triad. Each portal triad consists of an artery, vein, and bile ductule, and is accompanied by lymphatic vessels and a branch of the vagus nerve. Liver parenchyma consists of hepatocytes and hepatic sinusoids. Hepatic sinusoids drain into the central vein of each lobule. The liver is responsible for energy metabolism, synthesis of various substances (e.g., glucose, ketones, bile acid), glucose homeostasis regulation, nutrient storage, and the clearance/excretion of toxins (e.g., ethanol) and waste products. In fetuses, the liver is the site of erythropoiesis from 6 weeks' gestation until birth. During embryogenesis, the liver originates from the endoderm. The ligamentum teres forms from the obliterated umbilical vein and is located in the free edge of the falciform ligament.

Gross anatomytoggle arrow icon

General structure

  • Largest gland in the body
    • Weight: ∼ 1.2–1.5 kg in adults (2.6–3.3 pounds) [1][2]
  • Wedge-shaped
  • Consists of four lobes:
    • Right (largest)
    • Left
    • Quadrate
    • Caudate
  • Typically divided into 8 segments
  • Surrounded by the hepatic capsule (two layers)
    • Outer serous layer derived from peritoneum, which covers the entire liver (except the bare area of the liver)
    • Fibrous inner layer (the Glisson capsule) that covers the entire liver (including the bare area of the liver), the hepatic artery, portal vein, and bile ducts
  • Porta hepatis structures




Vasculature of the liver
Type of vessel Vessels

As part of the liver's dual blood supply, the portal vein allows tissue to remain oxygenated and preserve function in the event of an obstructed hepatic artery.


Distention of the capsule results in well-localized, sharp pain, as seen in ascites, inflammation, or hepatic cancer.


Microscopic anatomytoggle arrow icon

Zone 1 is first and zone 3 is last to receive O2.

Zone II is affected in yellow fever.


Functiontoggle arrow icon

Functions of the liver
Function Related biochemical pathways
Energy metabolism
Detoxification and clearance/excretion

For laboratory parameters for each of the functions, see “Parameters of hepatocellular damage,” “Parameters of cholestasis,” and “Parameters of hepatic synthesis” in “Liver function tests.”


Ethanol metabolismtoggle arrow icon

Breakdown of ethanol

Example of zero-order elimination (for alcohol dehydrogenase); : A constant amount of alcohol is metabolized per unit time (∼ 1 ounce of alcohol/hour). NAD+ is the limiting reactant for this pathway.

  1. Oxidation of ethanol to acetaldehyde by alcohol dehydrogenase
  2. Oxidation of acetaldehyde to acetate by acetaldehyde dehydrogenase
  3. Ligation of acetate and coenzyme A to acetyl-CoA by thiokinase under ATP consumption

When large quantities of alcohol are consumed, acetaldehyde builds up faster than it can be metabolized by acetaldehyde dehydrogenase. Excess acetaldehyde plays a major role in hangover symptoms.

Female individuals are more susceptible to ethanol intoxication than male individuals, even when consuming similar levels of alcohol. This is mainly because they have lower total body water and alcohol dehydrogenase activity than male individuals of comparable size. These physiological factors result in higher and more prolonged blood alcohol concentration, leading to faster intoxication. [10];
FOMEpizole: For Overdosing on Methanol or Ethylene glycol!

It is DISgusting to drink alcohol when taking DISulfiram!

Metabolic consequences of heavy ethanol consumption

When ethanol is metabolized, there is an increase in the NADH/NAD+ ratio in the liver. Heavy ethanol consumption and consequently excess NADH result in:

Embryologytoggle arrow icon

Clinical significancetoggle arrow icon

Referencestoggle arrow icon

  1. Sadler TW. Langman's Medical Embryology. Wolters Kluwer Health ; 2014
  2. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016
  3. Chung KW, Chung HM. Gross Anatomy. Lippincott Williams & Wilkins ; 2012
  4. McMartin K, Jacobsen D, Hovda KE. Antidotes for poisoning by alcohols that form toxic metabolites. Br J Clin Pharmacol. 2016; 81 (3): p.505-515.doi: 10.1111/bcp.12824 . | Open in Read by QxMD
  5. Goh ET, Morgan MY. Review article: pharmacotherapy for alcohol dependence - the why, the what and the wherefore. Aliment Pharmacol Ther. 2017; 45 (7): p.865-882.doi: 10.1111/apt.13965 . | Open in Read by QxMD
  6. White A. Gender Differences in the Epidemiology of Alcohol Use and Related Harms in the United States. Alcohol Research: Current Reviews. 2020; 40 (2).doi: 10.35946/arcr.v40.2.01 . | Open in Read by QxMD
  7. Molina DK, DiMaio VJM. Normal Organ Weights in Men. The American Journal of Forensic Medicine and Pathology. 2012; 33 (4): p.368-372.doi: 10.1097/paf.0b013e31823d29ad . | Open in Read by QxMD
  8. Molina DK, DiMaio VJM. Normal Organ Weights in Women. The American Journal of Forensic Medicine and Pathology. 2015; 36 (3): p.182-187.doi: 10.1097/paf.0000000000000175 . | Open in Read by QxMD
  9. Kumar V, Abbas AK, Aster JC. Robbins & Cotran Pathologic Basis of Disease. Elsevier Saunders ; 2014
  10. Drake R, Vogl AW, Mitchell AWM. Gray's Anatomy for Students International Edition. Elsevier Health Sciences ; 2009
  11. Hall JE. Guyton and Hall Textbook of Medical Physiology. Elsevier ; 2016

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