The human body is composed of dozens of organs, each performing specialized tasks necessary for life. Determining the “largest organ” often causes confusion because the answer depends on whether the classification is limited to internal structures or includes the body’s external covering. The largest internal organ, however, demands a closer look due to its immense physical presence and the hundreds of functions it performs.
Identifying the Largest Internal Organ
The largest organ overall in the human body is the skin, but when the classification is limited to organs inside the body cavities, the title belongs to the liver. This complex structure is found in the upper right quadrant of the abdomen, resting just below the diaphragm and mostly shielded by the lower rib cage. Anatomists classify it as a viscus, or internal organ.
The liver typically weighs between 1.2 and 1.8 kilograms in a healthy adult, making it the heaviest solid organ in the human body. Its dimensions usually span about 15 centimeters (6 inches) across, accounting for approximately 2 to 3 percent of an adult’s total body weight.
Essential Roles of the Liver in the Body
The massive size of the liver is directly correlated with its role as the body’s central metabolic and processing plant, performing over 500 different physiological functions. All blood leaving the stomach and intestines first passes through the liver via the portal vein, allowing the organ to screen and process virtually everything absorbed from the digestive tract.
A primary function is detoxification, where the liver neutralizes or modifies harmful substances, including drugs, alcohol, and environmental pollutants. It uses chemical processes to convert these toxic compounds into forms that can be safely excreted. For example, it converts poisonous ammonia, a byproduct of protein metabolism, into the less toxic compound urea, which is then eliminated by the kidneys.
The organ also manages the body’s energy supply through carbohydrate metabolism. It removes excess glucose from the bloodstream and stores it as glycogen via glycogenesis. When energy is required, the liver reverses this action through glycogenolysis, breaking down stored glycogen back into glucose to maintain stable blood sugar levels. Furthermore, it can create new glucose from non-carbohydrate sources like certain amino acids and fats (gluconeogenesis).
Beyond managing carbohydrates, the liver is central to lipid and protein metabolism. It synthesizes cholesterol and produces triglycerides, helping to manage fat transport throughout the body. The liver is also responsible for synthesizing many essential proteins, including albumin, which regulates fluid balance, and various blood clotting factors.
A key digestive function is the continuous production of bile, an alkaline fluid that is stored in the gallbladder before being released into the small intestine. Bile emulsifies dietary fats, breaking them into smaller droplets for easier digestion and absorption. The liver also serves as a major storage depot for vital nutrients, accumulating reserves of fat-soluble vitamins (A, D, E, and K) and minerals such as iron and copper.