The liver is the largest internal organ, weighing about three pounds in an adult and located in the upper right quadrant of the abdomen, beneath the diaphragm. It functions as the central chemical processing plant for the body, regulating vast arrays of substances that circulate through the bloodstream. Performing hundreds of complex operations, the liver maintains the body’s internal balance. It filters, converts, and synthesizes compounds, ensuring nutrients are utilized correctly and harmful substances are neutralized.
Anatomical Structure and Blood Flow
The liver is divided into two main lobes, which are further segmented into thousands of smaller units called lobules. This positioning allows the liver to handle the output of the entire digestive system.
The liver has a dual blood supply that is unusual compared to most other organs. The hepatic artery provides oxygenated blood to the liver tissue, accounting for about 25% of the total blood flow. The remaining 75% comes from the hepatic portal vein.
The hepatic portal vein directs nutrient-rich, but often toxin-heavy, blood from the gastrointestinal tract directly to the liver. This blood contains absorbed compounds from digested food, giving the liver the first opportunity to process them. After metabolic processing within specialized cells, known as hepatocytes, the blood drains out through the hepatic veins back toward the heart.
Essential Roles in Metabolism and Detoxification
The liver plays a central role in carbohydrate metabolism and energy regulation. It stores excess glucose from the bloodstream as glycogen. When blood sugar levels drop, the liver breaks down this stored glycogen back into glucose and releases it, ensuring a stable energy supply for the brain and muscles.
The liver also manages fat and protein processing. It synthesizes cholesterol and lipoproteins, which are necessary for cell structure and fat transport. The liver produces non-essential amino acids and synthesizes proteins, such as albumin and clotting factors, which are released into the blood.
The detoxification role of the liver involves neutralizing and eliminating harmful compounds. It filters the blood and uses enzyme systems, like the cytochrome P450 monooxygenases, to convert fat-soluble toxins, drugs, and alcohol into water-soluble forms. This conversion makes the substances easier to excrete through either bile or urine. For example, the liver converts ammonia, a byproduct of protein digestion, into the less toxic compound urea, which the kidneys then remove.
The liver also creates bile, an alkaline fluid composed of cholesterol and bile acids. Bile is secreted into the small intestine to emulsify dietary fats and aid in their digestion and absorption.
Major Diseases and Health Conditions
Metabolic dysfunction–associated steatotic liver disease (MASLD), previously known as NAFLD, is characterized by excessive fat buildup in liver cells not caused by heavy alcohol consumption. MASLD is strongly linked to metabolic risk factors such as obesity, Type 2 diabetes, and high cholesterol.
A more severe stage is Metabolic dysfunction-associated steatohepatitis (MASH), formerly known as NASH. MASH involves fat accumulation, inflammation, and cell damage, which can lead to scarring. While many people with MASLD remain asymptomatic, MASH carries a significant risk of progressing to cirrhosis.
Viral Hepatitis is caused by specific viruses that target liver cells, leading to inflammation. Hepatitis A is typically a short-term infection spread through contaminated food or water. Hepatitis B and C can become chronic infections transmitted through blood or bodily fluids, causing severe liver damage.
Cirrhosis is the final, irreversible stage of chronic liver disease, resulting from prolonged damage (e.g., MASH, chronic hepatitis, alcohol abuse). It occurs when healthy liver tissue is replaced by dense, non-functional scar tissue, a process called fibrosis. This scarring prevents the liver from functioning, leading to liver failure and increasing the risk of liver cancer.
Supporting Liver Resilience
Maintaining a healthy body weight helps prevent liver disease, particularly MASLD. Weight loss of even 5% to 10% can help reverse fat buildup in the liver. Focusing on a diet rich in whole foods while limiting processed foods, refined carbohydrates, and excessive sugars is beneficial, as these substances are readily converted into fat by the liver.
Alcohol consumption should be practiced with moderation, as excessive intake can overwhelm the organ. For adults, this means limiting consumption to no more than two standard drinks per day for men and one for women. Responsible use of over-the-counter medications is also crucial, especially acetaminophen, which is present in hundreds of products.
The maximum recommended dose of acetaminophen for healthy adults is 4,000 milligrams per day; exceeding this limit is a leading cause of drug-induced liver injury. Vaccination against Hepatitis A and B provides protection against these viral threats. Checking with a healthcare provider before taking new supplements or herbal remedies is prudent, as some can place stress on the liver.