The largest internal organ you cannot yet replace long-term
The liver is a vertebrate-only organ that clears toxins, builds proteins, stores nutrients and makes bile. In people it weighs about 1.5 kilograms, making it the heaviest internal organ and the largest gland, and as of 2018 nothing but a transplant could stand in for one that had completely failed.
It sits in the upper right of the abdomen under the diaphragm, mostly behind the lower right ribs. A healthy human liver is dark reddish-brown and wedge-shaped, about 15 centimetres wide, though size varies a great deal: the reference range runs from 970 to 1,860 grams for men and 600 to 1,770 grams for women. Beyond detoxification it handles carbohydrate metabolism, produces several hormones and stores nutrients such as glucose.
Bile is its contribution to digestion. This alkaline fluid of cholesterol and bile acids breaks dietary fat into small droplets; the gallbladder, a pouch under the right lobe, concentrates it and releases it into the duodenum. Blood arrives from two directions: oxygen-rich blood from the aorta through the hepatic artery, and nutrient-laden blood from the gut, spleen and pancreas through the portal vein. Both feed tiny channels called sinusoids that run through roughly hexagonal lobules, each built from millions of hepatocytes, the cells that fill 70 to 85 percent of the organ’s volume.
From above, the falciform ligament splits the liver into right and left lobes; from below, the caudate and quadrate lobes also show. Surgeons rely on an invisible boundary, Cantlie’s line, running from the gallbladder to the inferior vena cava, and on the Couinaud system, which divides the organ into eight segments, each with its own blood supply and bile drainage. A thin capsule named after the British doctor Francis Glisson wraps the whole organ.
About 60 percent of the body’s roughly 20,000 protein-coding genes are active in adult liver, and many liver-specific proteins are secreted into the blood as plasma proteins. Liver dialysis can bridge a short gap, but no artificial liver yet replaces the organ over the long term.
Source: Liver
