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Structure

Liver

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The liver is the largest internal organ and gland, central to metabolism, synthesis of plasma proteins, bile production and detoxification. It has a dual blood supply from the hepatic artery and portal vein.

Terminologia Anatomica (Latin): Hepar · Open in the 3D atlas

Location

It lies mainly in the right hypochondrium and epigastrium beneath the diaphragm, protected by the lower right ribs. Its diaphragmatic surface is smooth and its visceral surface bears the porta hepatis, gallbladder fossa and groove for the inferior vena cava; the bare area is without peritoneum.

Structure

Anatomically it has right and left lobes with the caudate and quadrate lobes. Functionally, Couinaud divides it into 8 segments (I to VIII), each with its own portal pedicle and biliary drainage, separated by the hepatic veins. The portal triad (hepatic artery proper, portal vein, bile duct) runs in the hepatoduodenal ligament and enters at the porta hepatis; histologically the hepatic lobule has a central vein and portal tracts at its corners.

Blood supply

About 70 to 75 percent of blood flow comes from the portal vein (nutrient-rich, partly deoxygenated) and about 25 to 30 percent from the hepatic artery proper (oxygenated), the two contributing roughly equally to oxygen supply. Blood mixes in the sinusoids and leaves by the right, middle and left hepatic veins, which drain directly into the inferior vena cava just below the diaphragm.

Innervation

The hepatic plexus carries sympathetic fibres from the coeliac plexus (mainly T7 to T10) and parasympathetic fibres from the anterior and posterior vagal trunks. The capsule (Glisson) is pain-sensitive, and pain from the diaphragmatic surface can be referred to the right shoulder through the phrenic nerve.

Function

The liver regulates glucose and lipid metabolism, synthesises albumin and most clotting factors, produces bile, metabolises drugs and hormones, converts ammonia to urea, stores glycogen and vitamins, and contains Kupffer cells of the mononuclear phagocyte system.

Clinical correlations

Cirrhosis raises portal pressure and opens portosystemic anastomoses (oesophageal varices, caput medusae, rectal veins) with ascites and encephalopathy. Viral and alcohol-related hepatitis, fatty liver disease and hepatocellular carcinoma are major diseases. Segmental anatomy guides imaging and resection, and liver size is assessed clinically by percussion and palpation below the right costal margin.

Common exam points

  • Couinaud: 8 functional segments (I caudate; II to IV left; V to VIII right), each with its own portal pedicle and biliary drainage.
  • Portal triad in the hepatoduodenal ligament: hepatic artery proper, portal vein, bile duct.
  • Dual blood supply: portal vein about 70 to 75 percent of flow, hepatic artery about 25 to 30 percent; hepatic veins drain to the IVC.
  • Anatomical lobes: right, left, caudate, quadrate; bare area lacks peritoneum.
  • Portal hypertension opens portosystemic anastomoses: oesophageal, rectal, para-umbilical.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. Elsevier, 11th edition (2020) — Tier 3 (textbook)
  4. Pawlina W. Histology: A Text and Atlas. Wolters Kluwer, 8th edition (2020) — Tier 3 (textbook)

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