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146 Human Body

A vital organ, the liver carries out hundreds of

essential chemical processes, adjusts the levels of

many substances in the blood, and produces a

digestive juice called bile. The liver is the body’s

heaviest organ, weighing about 1.5 kg (3½ lbs).

WHY IS THE LIVER A FACTORY?

The liver carries out so many tasks that scientists

compare it to a chemical factory. It filters blood from

the intestines and removes excess food and iron for

storage or for conversion into other substances.

It also removes debris, destroys poisons, worn-out

blood cells, and alcohol, and manufactures vitamin A

and many other chemicals vital to the body.

HOW DOES BLOOD GET TO THE LIVER?

Unlike other organs, the liver receives blood from

two major blood vessels. The hepatic artery brings

oxygen-rich blood from the heart. The hepatic portal

vein brings blood rich in digested nutrients from the

intestine. This means excess nutrients can be removed

and stored before blood circulates round the body.

WHAT IS INSIDE THE LIVER?

The liver is made up of thousands of lobules – tiny

hexagonal units about 1 mm (^1 ⁄ 25 in) wide. Each is

surrounded by a network of incoming blood vessels.

Blood filters through the lobule and drains away

through a vein in the middle.

WHAT IS BILE?

The liver makes a greenish-brown liquid called bile,

which is stored in a pouch called the gall bladder and

emptied into the small intestine, where it makes fats

mix with water and so helps digestion. Bile consists

of water, bile salts, acid, cholesterol, and a pigment

called bilirubin, which gives faeces their colour.

1 HORIZONTAL CROSS-SECTION THROUGH THE BODY

This scan shows a horizontal slice through the abdomen and gives an

impression of the liver’s size. The liver is the largest organ in the body

and takes up most of the space in the upper abdomen, just below the

ribs. The blue “hole” in the liver is the inferior vena cava – one of the

body’s largest veins.

2 LIVER CELLS

This magnified view shows red blood cells flowing through spaces

between the cells in a liver lobule. As the blood filters through the

lobule, the liver adjusts the levels of many different chemicals.

SCAN THROUGH THE ABDOMEN 3

This MRI scan shows a vertical slice

through the back of the abdomen.

Seen from the front, the liver is on the

left and the stomach is on the right. This

view shows a section of one end of the

liver, making it look smaller than it is.

Liver

The liver is not seen in

full in this image, which

shows a cross-section of

the back part of the liver

Kidneys lie beneath the

ribs at the back of

the abdomen

Stomach

Liver fills the

upper-left area

of the abdomen

Intestines

show up only

partially on

this scan

Vertebrae

of the spine

Aorta

carries blood

out of the heart

Vena cava

carries blood

to the heart

Red blood cells

pass through channels

called sinusoids

Vertebra

FIND OUT MORE. Circulation 134 • Digestion 144–145

liver