KS5 Biology
Lesson Plan 6 – Alcoholic Liver Disease
Science at Work in Healthcare
Post – 16 Science Education Pack
Resource Sheet 6.1 – The Living Liver
The liver is the largest internal 1 organ
in the human body and also the largest
gland. A healthy adult human liver
normally weighs between 1.4 and 1.6
kilograms. It is a soft pinky-brown,
almost triangular shaped organ.
It is located on the right side of the
upper abdomen, below the diaphragm
and to the right of the stomach.
Diagram 1. The location of
the liver
What does the liver do?
The liver is an important organ and it has been estimated that it carries out over 500
separate functions. It’s also an incredibly resilient organ and can continue working
satisfactorily even when only a small portion is actually functioning.
Some of the more important of these functions are:

Regulation of glucose in the blood – using insulin, the liver adds or removes
glucose from the blood depending on the circumstances. Liver cells either
convert glucose to glycogen for storage or it is broken down into carbon
dioxide and water for energy. Large excesses of glucose are converted into
lipids.

Regulation of lipids in the blood – liver cells either break down lipids in the
blood or modify them and send them to be deposited in various areas of the
body.

Regulation of amino acids – excess proteins and amino acids are destroyed
in the liver as the body is unable to store them. Ammonia is one of the
breakdown products of amino acids. This is highly toxic and cannot be
allowed to accumulate in the body. It is instead converted to urea through a
series of reactions known as the ornithine cycle.
1
The largest human organ is actually the skin.
KS5 Biology
Lesson Plan 6 – Alcoholic Liver Disease

Science at Work in Healthcare
Post – 16 Science Education Pack
Plasma protein synthesis – liver cells produce fibrinogen (necessary for blood
clotting) along with albumen and globulin which are important for
homeostasis.

Detoxification – as well as converting ammonia to urea, the liver can detoxify
a number of different compounds by absorbing them and then chemically
altering them into less harmful forms.

Heat production – the liver is a large organ, with a good blood supply and a
high metabolic rate. It is ideally suited for production and distribution of heat
through the body.

Bile production – bile is produced by liver cells and stored in the gall bladder.
It is very important for emulsifying fats in the small intestine.

Production of cholesterol – cholesterol is vital for the correct functioning of cell
membranes. Excess cholesterol is excreted in the bile. It can precipitate out
in the gall bladder, causing gall stones. These can block the bile duct and
cause obstructive jaundice. In this condition bilirubin is retained in the blood
and gives the skin a characteristic yellow colour.

Elimination of sex hormones – some are sent to the kidney for excretion in the
urine, others are chemically altered by the liver cells and some are expelled in
the bile.

Production of red blood cells – the liver is responsible for producing red blood
cells in the fetus. As the skeleton develops this function is taken over by the
bone marrow. However, the liver continues to store vitamin B12 which is
needed by the bone marrow for the production of red blood cells.

Elimination of haemoglobin – red blood cells are destroyed by phagocytes in
the blood vessels of the liver, spleen and bone marrow. The haemoglobin
from these cells is broken down by the liver to form a green pigment called
biliverdin which is further broken down to produce the yellowy brown pigment
bilirubin. This is excreted in the bile, giving it its characteristic colour.

Blood reservoir – the total volume of blood in an adult liver can vary between
300 cm3 and 1500 cm3. This is due to the elasticity of the blood vessels in the
liver and it allows the liver to control the amount of blood in circulation at any
one time.