Science · Medicine & the body

The liver

First successful transplant 1967

Medicine — hepatology and the digestive system

The largest internal organ and the largest gland in the body, weighing around 1.5 kg and lying in the upper right of the abdomen beneath the diaphragm. It receives a dual blood supply — oxygenated blood from the hepatic artery and nutrient-laden blood straight from the gut via the hepatic portal vein — and performs several hundred jobs at once: making bile, storing glycogen, synthesising albumin and most clotting factors, converting ammonia to urea, metabolising drugs and alcohol, and breaking down worn-out red cells. Alone among the body's solid organs, it can regenerate itself from a fraction of its mass.

How to spot them

▸Largest internal organ and largest gland; upper right quadrant, under the diaphragm
▸Dual supply: hepatic artery for oxygen, hepatic portal vein for nutrients from the gut
▸Four anatomical lobes — right, left, caudate, quadrate — and eight Couinaud segments
▸Hepatocytes, Kupffer cells, lobules and the portal triad
▸The only solid organ that regenerates — hence the Prometheus myth

Key facts

The largest internal organ and largest gland, weighing about 1.5 kg under the right dome of the diaphragm

Only the skin is a larger organ overall

Right, left, caudate and quadrate — four anatomical divisions, but eight functional segments in Couinaud's scheme

Surgeons work by the segments, anatomists by the lobes

An eagle ate it daily from the chained Prometheus, and it grew back each night

The myth reflects a real fact: it can regenerate from as little as a quarter of its mass

The bronze model found near Piacenza, marked out in regions for Etruscan diviners

Hepatoscopy — reading the future from a sacrificial animal's organ

Hepatocytes and Kupffer cells arranged in hexagonal lobules around a central vein

The microscopic unit, with a portal triad at each corner

The vessel that carries nutrient-rich blood directly from the intestines, bypassing the general circulation

The hepatic portal vein — about three-quarters of the organ's blood supply

Where glycogen is stored, urea is manufactured from ammonia, and albumin is synthesised

Three of its several hundred functions

Cirrhosis, jaundice and the yellow pigment bilirubin

Its characteristic failures; bilirubin comes from broken-down haemoglobin

Key ideas

It sits between the gut and the rest of the body, so everything absorbed from the intestine passes through it before reaching the general circulation — which is why it does the detoxifying and why some drugs are destroyed before they can work if swallowed.
Galen believed blood was manufactured here and consumed in the tissues; Harvey's demonstration of the circulation in 1628 destroyed that idea.

Quick-fire facts

•Weighs about 1.4–1.6 kg in an adult; the largest internal organ and the largest gland
•Has four anatomical lobes — right (the largest), left, caudate and quadrate — and eight segments in the Couinaud classification
•Receives roughly 25 per cent of its blood from the hepatic artery and 75 per cent from the hepatic portal vein; it drains via the hepatic veins into the inferior vena cava
•The functional unit is the lobule, with a central vein and portal triads (artery, portal vein branch and bile duct) at its corners
•Hepatocytes make up about 80 per cent of its mass; Kupffer cells are its resident macrophages
•Produces 500–1000 ml of bile a day, stored and concentrated in the gallbladder
•Synthesises albumin and almost all the clotting factors, so liver failure causes both oedema and bleeding
•Converts ammonia to urea in the urea cycle, and stores glycogen, iron as ferritin, and vitamins A, D and B12
•It is covered by Glisson's capsule; the falciform ligament separates the right and left lobes and carries the ligamentum teres, the remnant of the umbilical vein
•It can regenerate to full size from as little as a quarter of its mass, which makes living-donor transplantation possible
•Thomas Starzl performed the first successful human transplant of the organ in 1967, in Denver
•Wilson's disease is copper accumulation, haemochromatosis is iron accumulation, and cirrhosis is scarring after chronic injury
•The Greek 'hepar' gives hepatic and hepatitis; the Etruscan bronze Liver of Piacenza was a diviner's model

Drill it — 9 cards

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Sources

OpenStax, Rice University — Anatomy and Physiology 2e — Accessory Organs in Digestion: the Liver, Pancreas and Gallbladder
Henry Gray (Susan Standring, ed.) — Gray's Anatomy