Anatomy of the Liver

Location & Size

The liver resides in the upper right quadrant of the abdominal cavity, just beneath the diaphragm and protected by the ribcage. It extends across the midline toward the left upper quadrant. Averaging about 1.4 kg (3 lb) in adults, it measures roughly 15–20 cm horizontally and 25–30 cm vertically. Its position allows close contact with the stomach, gallbladder, duodenum, and right kidney while facilitating venous drainage into the inferior vena cava.

Reference: Gray’s Anatomy (42nd ed., 2020)

Lobes & Segments

The liver is divided into two principal lobes — right and left — separated by the falciform ligament. The right lobe is substantially larger and contains the caudate and quadrate lobes on its posterior and inferior surfaces. Functionally, the Couinaud classification describes eight segments, each with independent vascular inflow, outflow, and biliary drainage — crucial for surgical planning and transplantation.

• Right lobe: Metabolic and detoxification hub.
• Left lobe: Nutrient processing and bile synthesis.
• Caudate & quadrate: Specialized regions adjacent to the vena cava and gallbladder.

Blood Supply

The liver receives a dual blood supply: the hepatic artery proper (≈25%) provides oxygen-rich blood from the celiac trunk, while the portal vein (≈75%) delivers nutrient-rich blood from the digestive organs. Within hepatic sinusoids, these sources merge, allowing hepatocytes to extract nutrients and detoxify metabolites. Blood exits via the central veins → hepatic veins → inferior vena cava. This architecture supports both metabolism and filtration.

Clinical correlation: disruption leads to portal hypertension and variceal formation (Hall & Guyton Physiology, 15th ed., 2021).

Hepatic Cells

• Hepatocytes: ~80% of liver volume; perform metabolism, protein synthesis (albumin, clotting factors), and detoxification.
• Kupffer cells: Specialized macrophages in sinusoids that clear pathogens and debris.
• Stellate (Ito) cells: Store vitamin A; activate during injury to produce collagen (fibrosis).
• Endothelial cells: Line sinusoids; regulate exchange between blood and hepatocytes.
• Cholangiocytes: Bile-duct epithelial cells that modify bile composition.

Understanding these cell types underpins research in fibrosis and regenerative medicine (Moore et al., 2023).

Bile Production & Ducts

Hepatocytes continuously secrete bile containing bile salts, cholesterol, phospholipids, and bilirubin. Canaliculi drain into intrahepatic ducts → common hepatic duct → cystic duct → common bile duct → duodenum. Bile emulsifies fats and enables absorption of vitamins A, D, E & K. The gallbladder stores and concentrates bile between meals, releasing it via hormonal (CCK) signaling.

Reference: OpenStax Anatomy & Physiology (2024); NIDDK “Bile and Gallbladder Disorders” (2025).

Anatomical Features

The liver is anchored by several peritoneal ligaments: the falciform ligament (divides right and left lobes), coronary and triangular ligaments (attach to diaphragm), and the round ligament / ligamentum teres (a fetal umbilical-vein remnant). The portal triad — hepatic artery, portal vein, and bile duct — runs within the hepatoduodenal ligament. Understanding these landmarks is essential in hepatic surgery and imaging.

Functions of the Liver

• Metabolism: Regulates glucose (glycogen storage / gluconeogenesis), lipids, and amino acids.
• Detoxification: Biotransforms drugs, alcohol, and toxins into excretable forms.
• Bile production: Enables fat digestion and cholesterol elimination.
• Protein synthesis: Produces albumin and clotting factors.
• Storage: Vitamins A, D, B12 and iron (ferritin) reserves.
• Immune function: Kupffer cells filter pathogens from portal blood.

Reference: Hall & Guyton Textbook of Medical Physiology (15th ed., 2021).

Clinical Significance

Knowledge of hepatic anatomy is vital in diagnosing and treating conditions such as viral hepatitis, fatty liver disease, cirrhosis, and hepatocellular carcinoma. Imaging modalities (ultrasound, CT, MRI) rely on segmental anatomy, while transplant surgeons depend on precise vascular mapping. Preservation of functional parenchyma during resection improves outcomes and underscores the liver’s regenerative capacity.