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Liver

The position of the liver inside the bodyEvery drop of blood coming from the intestines must pass through the liver before it goes anywhere else. The body’s largest internal organ, the liver performs over 500 functions. Its main job is to process blood rich in nutrients arriving directly from the digestive system. It also makes substances needed by body cells and removes poisons, drugs, and debris from the blood before passing it to the rest of the body.



What the liver does

Blood that is rich in nutrients absorbed from the small intestines is brought to the liver by the portal vein. One of these nutrients is glucose, the body’s main energy source. This is converted by the liver cells into a substance called glycogen. It is stored in the liver when levels in the blood are too high, and released into the blood when levels are too low. Excess amino acids, which come from protein digestion, cannot be stored but are converted into carbohydrates and a waste substance called urea which is passed to the kidneys, from where it leaves the body in urine.
The liver, showing the blood vessels inside.The liver stores certain vitamins, such as vitamins A and D, and minerals, including iron and copper. It makes the proteins found in blood plasma, including those involved in blood clotting. It also collects up old, worn-out red blood cells and cleans out poisons, drugs, alcohol and other impurities from the bloodstream. Some of the chemical waste is turned into bile, which is stored in the gall bladder. This empties out back into the small intestine where it helps the digestion of fats by mixing with them.
 

In medieval times the liver was thought to be the centre of courage in the body. By the 17th century, "lily-livered" came to mean timid or cowardly, because a lily-coloured (pale) liver would supposedly be bloodless and weak.

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