liver

The liver is a large, reddish-brown organ located in the upper right quadrant of the abdominal cavity, beneath the diaphragm. It weighs about 1.3 to 1.5 kilograms in adults and performs a wide range of metabolic, synthetic, and detoxification tasks. The liver is divided into lobes, with the right and left lobes being the largest, and smaller caudate and quadrate lobes. It is connected to the digestive tract via the portal vein, hepatic artery, and bile ducts, collectively forming the portal triad.

The microscopic structure consists of hepatic lobules, plates of hepatocytes arranged around a central vein, separated by sinusoids. Blood from the portal vein and hepatic artery flows through sinusoids, where hepatocytes process nutrients and toxins before draining into the central vein. Kupffer cells in the sinusoids remove pathogens and debris. Bile produced by hepatocytes drains into bile canaliculi, then into the bile ducts, and onward to the gallbladder or intestine.

Major functions include: metabolism of carbohydrates, lipids, and proteins; storage of glycogen, vitamins, and minerals; synthesis of plasma proteins (including albumin and clotting factors), and urea production; detoxification and drug metabolism via cytochrome P450 enzymes; conjugation of bilirubin for excretion; and bile production for fat emulsification. The liver also plays a role in immune defense and hormone metabolism and can regenerate after injury.

Clinically, liver health is assessed by enzymes and bilirubin levels, and diseases such as hepatitis, fatty liver disease, cirrhosis, and liver failure can impair multiple functions.