Page 23 - How It Works - Book of Amazing Answers To Curious Questions, 12

Science*------------------Q�

Why is the

liver a 'high

demand'
organ?

he liver deals with a massive amount of
blood. It is unique because it has two blood
T supplies. 75 per cent of this comes directly
from the intestines !via the hepatic portal vein)
which carries nutrients from digestion, which the
liver processes and turns into energy. The rest
comes from the heart, via the hepatic artery
!which branches from the aorta), carrying oxygen
that the liver needs to produce this energy. The
blood flows in tiny passages in between the liver
cells where the many metabolic functions occur.
The blood then leaves the liver via the hepatic
veins to flow into the biggest vein in the body- the
inferior vena cava. 0
Liver lobules
3. Sinusoids 1. The lobule
These blood-filled This arrangement of
channels are lined by blood vessels, bile The functional unit that
hepatocytes and provide ducts and hepatocytes
the site of transfer of form the functional unit performs the liver's tasks
molecules between of the liver.
blood and liver cells.
he liver is considered a 'chemical factory;
2. The as it forms large complex molecules from
hepatocyte
These highly active T smaller ones brought to it from the gut via
4. Kupffer cells cells perform all of the blood stream. The functional unit of the liver
the liver's key is the lobule - these are hexagonal-shaped
These specialised cells
sit within the sinusoids metabolic tasks. structures comprising of blood vessels and
and destroy any
bacteria which are sinusoids. Sinusoids are the specialised areas
contaminating blood. where blood comes into contact with the
hepatocytes, where the liver's biological
processes take place. 0
9. Central vein
Blood from sinusoids, 5. Hepatic
now containing all of artery branch
its new molecules,
flows into central Blood from here supplies
veins which then flow oxygen to hepatocytes and
carries metabolic waste
into larger hepatic which the liver extracts.
veins. These drain into
the heart via the
inferior vena cava.
6. Bile duct
Bile, which helps digest fat, is made
in hepatocytes and secreted into bile
ducts. It then flows into the
gallbladder for storage before being
secreted into the duodenum.
7. Portal vein
This vein carries nutrient-rich
8. The portal triad blood directly from the
The hepatic artery, portal vein and bile duct are known as intestines, which flows into
the portal triad. These sit at the edges of the liver lobule sinusoids for conversion into
and are the main entry and exit routes for the liver. energy within hepatocytes.

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