The liver is the body’s largest solid internal organ and its primary metabolic “factory.” Located in the Right Upper Quadrant (RUQ) of the abdomen, tucked safely beneath the diaphragm and the lower rib cage, it performs over 500 vital functions.
The liver is a dark reddish-brown, wedge-shaped organ roughly the size of a rugby ball.
Weight: Approximately 1.8 kg in men and 1.3 kg in women (about 2% of total body weight).
Filtration: It filters an incredible 1.7 liters of blood per minute.
Cellular Makeup: It is composed of roughly 300 billion specialized cells, primarily hepatocytes.
Traditionally, the liver is divided into four lobes based on surface landmarks:
Right Lobe: The largest lobe.
Left Lobe: Smaller and flatter, extending toward the stomach.
Quadrate Lobe: Located on the inferior surface.
Caudate Lobe: Located on the posterior surface.
In modern surgery, the liver is divided into eight functional segments based on the Couinaud Classification.
Segmental Autonomy: Each segment has its own dedicated blood supply (dual inflow), biliary drainage, and venous outflow.
Surgical Significance: This “independence” allows surgeons to perform a partial hepatectomy (removing a diseased segment) while leaving the remaining segments fully functional.
The liver is essential for survival, managing everything from energy to detoxification:
Protein Synthesis: Produces Albumin (maintains blood volume) and Clotting Factors (Fibrinogen and Prothrombin).
Waste Removal: Breaks down hemoglobin to create Bilirubin, which is excreted via bile.
Glucose Regulation: Stores excess sugar as Glycogen and releases it when the body needs an energy boost.
Hormone Production: Secretes IGF-1 (growth) and Angiotensinogen (blood pressure regulation).
Detoxification: Processes alcohol and drugs into less harmful substances.
Unlike most organs, the liver receives blood from two distinct sources:
Hepatic Portal Vein (75%): Delivers deoxygenated, nutrient-rich blood directly from the digestive tract.
Hepatic Artery (25%): Provides oxygenated blood to sustain the liver tissues.
Clinical Variation: Anatomy often varies; some individuals have a “replaced” right hepatic artery that originates from the superior mesenteric artery (SMA) instead of the celiac trunk.
After blood is processed in the liver, it exits through the Right, Middle, and Left Hepatic Veins. These veins empty directly into the Inferior Vena Cava (IVC), returning blood to the heart. Understanding this drainage is critical for placing IVC filters or performing liver resections.
The Porta Hepatis is the “gateway” to the liver. This transverse fissure on the underside of the liver is where three major structures enter or exit:
The Portal Vein
The Hepatic Artery
The Common Hepatic Duct
The liver continuously produces bile, a bitter fluid required for fat digestion.
Flow: Bile travels from small ducts into the Right and Left Hepatic Ducts, which merge into the Common Hepatic Duct.
Storage: The Cystic Duct carries bile to the gallbladder for storage until it is needed in the small intestine.
Several peritoneal folds, or ligaments, anchor the liver to the diaphragm and abdominal wall:
Falciform Ligament: Separates the right and left lobes anteriorly.
Coronary and Triangular Ligaments: Attach the liver superiorly to the diaphragm.
The liver is the only internal organ capable of total regeneration.
The 75% Rule: If up to 75% of the liver is surgically removed or damaged, it can grow back to its original size in just 6 to 8 weeks.
Mythology Connection: This biological phenomenon mirrors the Greek myth of Prometheus, whose liver was eaten daily by an eagle only to grow back every night.
Palpation: In most healthy adults, the liver is not palpable because it is protected by the rib cage. However, in slim individuals, the inferior edge may be felt just below the right costal margin during a deep breath.
Hepatomegaly: An enlarged liver (hepatomegaly) that is easily felt below the ribs can indicate cirrhosis, hepatitis, or congestive heart failure.
Foetal Fact: In the womb, the liver is the primary site for Haematopoiesis (blood cell production) before the bone marrow takes over later in development.
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