Your liver gets blood from two pipes, stores your sugar overnight, turns poison into waste and can grow back after most of it is removed. The liver is the largest organ inside you, about 1.2 to 1.5 kg, under your right ribs.
Your liver gets blood from two pipes, stores your sugar overnight, turns poison into waste and can grow back after most of it is removed. Zoom from the whole organ into its tiny hexagons and watch blood and bile flow opposite ways.
LiverClearOpened 11 Aug 202615 min to playFree · no sign-up
In 60 seconds
Two blood supplies
The liver is the largest organ inside you, about 1.2 to 1.5 kg, under your right ribs. About three-quarters of its blood comes straight from the gut through the portal vein, and a quarter fresh from the heart through the hepatic artery: about 1.35 litres a minute in all, roughly a quarter of the heart's output.
100,000 tiny hexagons
The liver is built from 50,000 to 100,000 six-sided lobules, 1 to 2 mm across. Blood trickles in from the corners to a central vein, past plates of liver cells, while bile flows the other way to the corners. Kupffer cells in the channels catch almost every bacterium from the gut.
The sugar bank
After meals, insulin tells the liver to store glucose as glycogen, up to about 100 g. Between meals and overnight, glucagon tells it to release glucose and make new glucose, keeping blood sugar steady at about 70 to 140 mg/dL. It also makes albumin, clotting factors and cholesterol.
Cleaning the blood
The liver turns toxic ammonia into urea for the kidneys to remove, breaks down medicines and alcohol at a roughly steady pace that no trick can speed up, and turns the pigment of old red blood cells into bilirubin, which leaves in bile. If bile backs up, skin and eyes turn yellow: jaundice.
Bile breaks up fat
The liver makes about half a litre to a litre of bile a day. The gallbladder stores and concentrates it, then squeezes it into the gut after a meal. Bile salts split fat into droplets smaller than a thousandth of a millimetre, giving digestive enzymes up to 1,000 times more surface.
Regrowing and going wrong
Up to about 70% of a liver can be removed and the rest grows back to about full size in two to three months, which makes living-donor transplants possible. Fatty liver affects about 3 in 10 adults, hepatitis B and C viruses infect hundreds of millions, and years of damage can end in cirrhosis. For your own liver, talk to a doctor.
The history
4,000 years from clay livers used to read the future to pills that cure hepatitis C and livers that regrow after being shared.
The biggest organ inside you, with two blood supplies and a green drain.
Your liver is the largest organ inside your body: about 1.2 to 1.5 kg in an adult, the weight of a big bag of sugar. It sits in the upper right of your belly, tucked under your right ribs and pressed up against the dome of your diaphragm. We are looking at it from the front, so the patient's right is on your left.
It has a big right lobe and a thinner left lobe that reaches across over the stomach. A fold of tissue, the falciform ligament, marks the line between them on the front. Two small lobes hide round the back and underneath: the caudate and the quadrate. Tucked under the right lobe is a little green bag, the gallbladder.
The liver is unusual because it gets blood from two pipes. The hepatic artery brings about a quarter of it, fresh with oxygen. The portal vein brings about three-quarters, straight from your stomach and intestines, full of everything you have just digested. So the liver gets first look at your food before the rest of your body does. About 1.35 litres a minute pass through it, roughly a quarter of all the blood your heart pumps (see HeartClear). It all leaves through the hepatic veins into the inferior vena cava, the big vein that runs up to the heart.
A second set of tubes carries bile the other way, out of the liver: the hepatic ducts join into the common bile duct, which empties into the first part of the small intestine, the duodenum.
Blood flows in to the middle, bile flows out to the corners.
Zoom into the liver and it is built from tiny six-sided units called lobules, each about 1 to 2 mm across. There are 50,000 to 100,000 of them, packed together like a honeycomb.
At every corner of a lobule sits a portal triad: three little tubes side by side. A branch of the portal vein (purple, from the gut), a branch of the hepatic artery (red, with oxygen) and a bile ductule (green). In the middle runs the central vein.
Liver cells, called hepatocytes, are stacked in thin walls, or plates, that fan out from the centre like the spokes of a wheel. Between the plates run leaky capillaries called sinusoids. Blood from the corners trickles inwards along them to the central vein, and every liver cell gets to take things out of it and put things back. Meanwhile the cells make bile and send it outwards in tiny channels between them, the bile canaliculi, to the ductules at the corners. Blood in, bile out: two streams going opposite ways and never mixing.
Watch the yellow star-shaped cells in the sinusoids. They are Kupffer cells, the liver's own germ-eaters. Blood from the gut carries some bacteria, and Kupffer cells swallow almost all of them: fewer than 1 in 100 get through.
Store sugar after meals, pay it back between them, and build what blood needs.
Your brain burns sugar (glucose) all day and all night, but you only eat a few times a day. The liver bridges the gap like a bank.
After a meal, glucose floods in through the portal vein. The pancreas (see PancreasClear) releases the hormone insulin, and the liver takes glucose in and links thousands of them into big branching molecules called glycogen, stored as granules inside its cells. A full liver holds about 100 g of glycogen. On an ordinary day the store swings roughly between half and three-quarters full.
Between meals and overnight, blood sugar starts to dip. The pancreas switches to glucagon, and the liver breaks glycogen back down and releases glucose. It can also make brand-new glucose from bits of protein and fat, called gluconeogenesis. That is why your blood sugar stays around 70 to 140 mg/dL all day, even while you sleep. How your body turns food into energy is in EnergyClear.
The liver is a factory too. It makes albumin, the most common protein in your blood (about 10 to 15 g a day), which holds water in your blood vessels and carries things around. It makes most of the clotting factors that stop you bleeding, and much of your cholesterol, which every cell needs for its walls.
Ammonia into urea, alcohol into acetate, old red cells into bile.
Everything the portal vein brings from the gut passes through the liver before it reaches the rest of you, so the liver acts as a filter and a chemical plant. It changes harmful things into harmless ones, or into forms that can leave the body.
Ammonia. When your body breaks down protein, it makes ammonia, which is poisonous to the brain. Liver cells feed it into a loop of reactions called the urea cycle and turn it into urea, which is harmless. The blood carries urea to the kidneys, which pass it out in urine (see KidneyClear).
Alcohol and medicines. Enzymes in liver cells break down most medicines, and alcohol. Alcohol dehydrogenase turns alcohol into acetaldehyde, which is toxic, and a second enzyme turns that into harmless acetate. The liver works at a roughly steady pace: for many adults something like 7 to 10 g of alcohol an hour, though it varies a lot from person to person. Coffee, cold showers or water do not speed it up. Only time does.
Old red blood cells. A red cell lives about 120 days. Worn-out ones are swallowed by macrophages, and their red pigment becomes a yellow one, bilirubin. The liver packages bilirubin and sends it out in bile, which is why stool is brown. If bile can’t drain, bilirubin builds up in the blood and the skin and whites of the eyes turn yellow. That is called jaundice, and it always needs a doctor to find the cause.
Made all day, stored in the gallbladder, poured on fat when you eat.
Your liver makes about half a litre to a litre of bile every day, a yellow-green liquid made of water, bile salts, cholesterol and the yellow pigment bilirubin. It trickles out through the bile ducts.
Between meals, most of it backs up into the gallbladder, a little bag under the liver that holds about 30 to 50 mL. There the bile is concentrated 5 to 10 times as water is pulled out of it, so it turns a darker green.
When food with fat reaches the small intestine, the gut releases a hormone called CCK. The gallbladder squeezes, a ring of muscle at the end of the duct (the sphincter of Oddi) relaxes, and bile pours into the duodenum. What happens before that is in StomachClear, and what comes after in IntestineClear.
Fat and water don't mix, so fat sits in big blobs that enzymes can only nibble from the outside. Bile salts work like washing-up liquid: one end loves water, the other loves fat. They coat the fat and break it into tiny droplets, called emulsification. The same amount of fat now has a far bigger surface, so the fat-digesting enzyme lipase from the pancreas can get to work. Droplets under a thousandth of a millimetre give up to 1,000 times more surface.
Sometimes cholesterol in the gallbladder hardens into gallstones. Many people never notice them, but a stone stuck in a duct can cause strong pain, and that needs a doctor.
The organ that grows back, and the slow damage it can’t always undo.
The liver has a superpower: it can grow back. Up to about 70% of it can be removed, and the rest grows until the liver is roughly its old size again, in about two to three months in people. The leftover lobes swell up; the missing piece doesn't regrow in its old shape. In the Greek myth, an eagle ate the liver of Prometheus every day and it grew back every night. That is why a healthy adult can give part of their liver to someone else, a living-donor transplant, and both livers grow.
But the liver can be hurt slowly, often with no signs for years. In fatty liver disease (now called MASLD), fat builds up inside liver cells. It is very common: about 3 in 10 adults worldwide, and studies in India put it near 4 in 10. Being active and eating well are linked with a healthier liver, and early fatty liver can often improve.
Hepatitis means an inflamed liver. The viruses hepatitis B and C spread through blood and, for B, from mother to baby and through sex. The WHO estimates about 240 million people live with hepatitis B and 47 million with hepatitis C. A vaccine protects against hepatitis B (it is part of India's childhood vaccine schedule), and medicines now cure more than 95% of hepatitis C.
Years of damage from fat, heavy drinking or viruses can lead to scarring and finally cirrhosis: a hard, lumpy liver that can no longer do its jobs well. Only a doctor can tell how a liver is doing, with blood tests and scans, so if you are ever worried, talk to one.
From the stomach and intestines, through the portal vein. About three-quarters arrives through the portal vein, carrying what you have just digested. Only about a quarter comes through the hepatic artery.
Where in your body is the liver?
Upper right of the belly, under the ribs. It sits under the right ribs, just below the diaphragm, with its left lobe reaching across the middle.
Which way does bile travel?
Out of the liver, down the bile ducts to the small intestine. Bile is made in the liver and drains out through the bile ducts, stored on the way in the gallbladder, into the duodenum.
In a lobule, which way does blood flow?
From the corners in to the central vein. Blood enters at the portal triads on the corners and trickles through the sinusoids into the central vein.
And bile?
The opposite way: out to the bile ductules at the corners. Bile flows outwards in canaliculi between the cells, the opposite way to the blood, and never mixes with it.
What do Kupffer cells do?
Swallow bacteria and old cells in the blood. They are macrophages in the sinusoids. They catch almost all the bacteria that arrive from the gut.
After a meal, what does the liver do with extra glucose?
Stores it as glycogen. Insulin tells liver cells to link glucose into glycogen and store it for later.
Why doesn’t your blood sugar crash at night while you sleep?
The liver releases stored glucose and makes new glucose. Glucagon tells the liver to break down glycogen and make new glucose, keeping blood sugar steady.
Which of these does the liver make?
Albumin and clotting factors. The liver builds most blood proteins, including albumin and clotting factors. Insulin comes from the pancreas.
What does the liver turn ammonia into?
Urea, which the kidneys remove. The urea cycle turns toxic ammonia into harmless urea, which leaves in urine.
Which of these speeds up how fast the liver clears alcohol?
None of them: only time. The liver’s enzymes work at a roughly steady pace. Coffee may make someone feel more awake, but the alcohol is still there.
Why can skin turn yellow in jaundice?
Bilirubin from old red cells builds up because it can’t leave in bile. Bilirubin normally leaves in bile. If it backs up, it spreads into the skin and eyes. Jaundice always needs a doctor.
What does the gallbladder do?
Stores and concentrates bile between meals. The liver makes bile; the gallbladder stores it and pulls water out to concentrate it.
How do bile salts help digest fat?
They break it into tiny droplets, giving enzymes much more surface. Emulsification: smaller droplets mean far more surface for lipase to work on.
Split one fat drop into 1,000 equal drops. The total surface becomes…
10 times bigger. Each drop is 10 times narrower, so the surface grows by the cube root of 1,000, which is 10. Splitting into a billion gives 1,000 times.
About how much of a liver can be removed and still grow back?
Up to about 70%. The remaining liver enlarges until it is close to its old size, in about two to three months in people.
Which liver virus can a vaccine protect you from?
Hepatitis B. The hepatitis B vaccine gives nearly complete protection. There is no vaccine for hepatitis C, though medicines now cure most cases.
Which is true about fatty liver?
It is common, often silent, and early stages can often improve. About 3 in 10 adults worldwide have it, usually without symptoms. A doctor can check with blood tests and scans.
Words worth knowing
Portal vein
The vein that brings blood from the stomach, intestines and spleen to the liver, about three-quarters of its supply.
Hepatic artery
The artery that brings oxygen-rich blood to the liver, about a quarter of its supply.
Lobule
A tiny six-sided unit of the liver, 1 to 2 mm across, with portal triads at its corners and a central vein in the middle.
Hepatocyte
The main liver cell, which stores sugar, builds proteins, makes bile and breaks down toxins.
Glycogen
A branching chain of glucose units: the liver's store of sugar, up to about 100 g.
Insulin and glucagon
Hormones from the pancreas: insulin tells the liver to store glucose, glucagon tells it to release glucose.
Urea cycle
A loop of reactions in liver cells that turns toxic ammonia into harmless urea.
Bile
A yellow-green liquid made by the liver. Its bile salts break fat into tiny droplets so it can be digested.
Cirrhosis
Severe, lasting scarring of the liver after years of damage, which stops it working well.
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