Lopez_Liver+Anatomy

1. Gross Anatomy

  • Largest internal organ (~1.5 kg).

  • Location → RUQ, beneath diaphragm, protected by ribs 7–11.

  • Surfaces:

    • Diaphragmatic (convex, anterior/superior).

    • Visceral (concave, contacts stomach, duodenum, colon, kidney).

  • Lobes: Right, Left, Caudate, Quadrate.

  • Ligaments:

    • Falciform → connects to anterior abdominal wall.

    • Round ligament (ligamentum teres) → remnant of fetal umbilical vein.

    • Coronary ligaments → attach to diaphragm.

2. Blood Supply

  • Dual input:

    • Portal vein (75%) → nutrient-rich, low O₂.

    • Hepatic artery (25%) → oxygenated blood.

  • Drainage: Central veins → hepatic veins → IVC.

  • Pearl: Portal hypertension → collateral flow (esophageal varices, hemorrhoids, caput medusae).

3. Microscopic Anatomy

  • Classic Lobule (hexagon):

    • Central vein in center.

    • Portal triads at corners (portal vein, hepatic artery, bile duct).

  • Blood flow: Portal triad → sinusoids → central vein.

  • Bile flow: Hepatocytes → canaliculi → bile ducts (opposite to blood).

Portal Acinus (functional unit)

  • Zone 1 (periportal): best O₂, nutrients → oxidative metabolism, gluconeogenesis.

  • Zone 2: transitional, sensitive to yellow fever.

  • Zone 3 (centrilobular): poor O₂ → ischemia, alcohol, acetaminophen toxicity (CYP450).

  • Pearl: Pathology often localized by zone.

4. Cellular Players

  • Hepatocytes → metabolism, bile production, protein synthesis.

  • Kupffer cells (macrophages) → phagocytosis, immune surveillance.

  • Stellate (Ito) cells → store Vit A in Space of Disse; activated → fibrosis.

  • Sinusoidal endothelial cells → fenestrated, allow exchange.

  • Cholangiocytes → bile duct epithelium.

5. Biliary System

  • Flow: Canaliculi → bile ductules → right & left hepatic ducts → common hepatic duct.

  • Joins cystic duct → common bile duct → duodenum (via ampulla of Vater).

  • Pearl: Obstruction → jaundice, cholangitis, biliary cirrhosis.

6. Clinical Anatomy

  • Pringle maneuver: Clamp hepatoduodenal ligament (portal triad) to control bleeding.

  • Couinaud segments: Liver divided into 8 surgical segments, each with own vascular inflow/outflow → basis for resection.

  • Imaging pearls:

    • CT/MRI often shows lesions relative to segments.

    • Caudate lobe drains directly to IVC (can hypertrophy in cirrhosis).

✅ Quick Pearls

  • Blood vs bile flow: opposite directions.

  • Zone 3 → ischemia & toxins.

  • Kupffer cells → immune defense.

  • Stellate cells → fibrosis in cirrhosis.

  • Portal triad = vein, artery, bile duct.