Introduction to Health and Safety at Work

14.5.3 The cardiovascular system
The blood system uses the heart to pump blood around 
the body through arteries, veins and capillaries. Blood is 
produced in the bone marrow and consists of a plasma 
within which are red cells, white cells and platelets. The 
system has three basic objectives:
➤
to transport oxygen to vital organs, tissues and the 
brain and carbon dioxide back to the lungs (red cell 
function);
➤
to attack foreign organisms and build up a defence 
system (white cell function);
➤
to aid the healing of damaged tissue and prevent 
excessive bleeding by clotting (platelets).
There are several ways in which hazardous substances 
can interfere with the cardiovascular system. Benzene 
can affect the bone marrow by reducing the number 
Trachea
Primary
bronchus
Lobar
bronchus
Passages
of air
conduction
Bronchioles
Respiratory
bronchioles
Alveolar duct
Alveolus
Lobule
Segmental
bronchus
Passages
where
gases
exchange
Figure 14.2
Continued.
Brain
Spinal cord
Peripheral nerves
Central nervous system
Peripheral nervous system
Figure 14.3
The nervous system.
Blood vessels
Heart
Figure 14.4
The cardiovascular system.

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Introduction to Health and Safety at Work
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of blood cells produced. Carbon monoxide prevents 
the red cells from absorbing suffi cient oxygen and the 
effects depend on its concentration. Symptoms begin 
with headaches and end with unconsciousness and 
possibly death.
14.5.4 The urinary system
The urinary system extracts waste and other products 
from the blood. The two most important organs are the 
liver (normally considered part of digestive system) and 
the kidneys, both of which can be affected by hazardous 
substances within the bloodstream.
The liver removes toxins from the blood, maintains 
the levels of blood sugars and produces protein for the 
blood plasma. Hazardous substances can cause the 
liver to be too active or inactive (e.g. xylene), lead to liver 
enlargement (e.g. cirrhosis caused by alcohol) or liver 
cancer (e.g. vinyl chloride).
The kidneys fi lter waste products from the blood 
as urine, regulate blood pressure and liquid volume in 
the body and produce hormones for making red blood 
cells. Heavy metals (e.g. cadmium and lead) and organic 
solvents (e.g. glycol ethers used in screen printing) can 
restrict the operation of the kidneys possibly leading to 
failure.
14.5.5 The skin
The skin holds the body together and is the fi rst line of 
defence against infection. It regulates body temperature, 
is a sensing mechanism, provides an emergency food 
store (in the form of fat) and helps to conserve water. 
There are two layers – an outer layer called the epider-
mis (0.2 mm) and an inner layer called the dermis (4 mm). 
The epidermis is a tough protective layer and the dermis 
contains the sweat glands, nerve endings and hairs.
The most common industrial disease of the skin 
is 
dermatitis
(non-infective dermatitis). It begins with 
a mild irritation on the skin and develops into blisters 
which can peel and weep becoming septic. It can be 
caused by various chemicals, mineral oils and solvents. 
There are two types:
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