Liver Anatomy: Lobes and Segmentation

• The liver, the largest internal organ in the human body, is located in the upper right quadrant of the abdomen, beneath the diaphragm and on top of the stomach, right kidney, and intestines
• The liver plays a crucial role in metabolism, detoxification, and storage of nutrients

Lobes of the Liver

• The traditional anatomical division classifies the liver into two major lobes: the right lobe and the left lobe
• These lobes are separated by the falciform ligament, which attaches the liver to the anterior abdominal wall
• The right lobe is significantly larger than the left lobe
• The caudate and quadrate lobes are also present

Couinaud's Liver Segmentation

• A more functional and surgically relevant system divides the liver into eight independent segments
• Each segment has its own vascular inflow, outflow, and biliary drainage
• This segmentation is based on the distribution of the portal vein and hepatic veins
• The segments are numbered I to VIII in a clockwise manner, with segment I being the caudate lobe

Vasculature of the Liver

• The liver has a dual blood supply, receiving blood from both the hepatic artery and the portal vein
• The hepatic artery supplies oxygenated blood, while the portal vein carries nutrient-rich blood from the digestive system
• After processing in the liver, blood drains into the central veins, which converge into the hepatic veins
• The hepatic veins then empty into the inferior vena cava

Ligaments of the Liver

• Several ligaments support the liver and attach it to surrounding structures
• The falciform ligament attaches the liver to the anterior abdominal wall and contains the ligamentum teres (remnant of the umbilical vein)
• The coronary ligament attaches the liver to the diaphragm
• The triangular ligaments (right and left) are formed by the meeting of the upper and lower layers of the coronary ligament
• The lesser omentum connects the liver to the lesser curvature of the stomach and the duodenum, consisting of the hepatogastric and hepatoduodenal ligaments

Microscopic Anatomy

• The liver is composed of functional units called lobules
• Each lobule consists of hepatocytes arranged in plates radiating from a central vein
• Between the plates of hepatocytes are sinusoids, which are specialized capillaries that allow blood to come into close contact with the hepatocytes
• Kupffer cells, a type of macrophage, reside within the sinusoids and play a role in removing debris and pathogens from the blood
• Bile canaliculi are small channels between hepatocytes that collect bile, which is then drained into bile ducts

Functional Divisions

• Metabolizes carbohydrates, fats, and proteins
• Detoxifies drugs and toxins
• Synthesizes bile, which is essential for fat digestion
• Stores glycogen, vitamins, and minerals
• Produces clotting factors and other important proteins