WJEC GCSE Biology 3 The Heart and Circulatory System

the heart Triple bioliogy revision notes

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Megan Nolan
Triple Biology Revision Notes:
The Circulatory System
The double circulatory system:
Most mammals, including humans have a double circulatory
system. There are two separate circulations, one to the
lungs (the pulmonary circulation) to oxygenate the blood
and the other to the organs to supply oxygen. This means
that the right side of the heart is smaller as it only has to
pump blood to the lungs, whereas the left side has to
pump to the whole body.
Functions of the blood:
White Blood Cell-
Defence against diseases
Produce antibodies to fight microbes
Produce antitoxins to neutralise toxins produced
by microbes
Have a flexible shape to engulf microorganisms; they completely surround the
microorganism and then digest it.
Red Blood cells-
They transport oxygen from the lungs to all the cells in the body
They are small and have a biconcave shape to increase surface area, so they can absorb and
release oxygen quicker
They have no nucleus so there is more space for carrying oxygen
Very flexible so they can pass through small capillaries
Contain haemoglobin which is what bonds to oxygen to give oxyhaemoglobin; in the cells the
reverse happens to release the oxygen
Haemoglobin contains a lot of iron and is what gives blood its colour

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Megan Nolan
Plasma is a pale yellow liquid which carries everything that needs transporting around the
· Red and white blood cells
· Platelets
· Water
· Food products such as glucose and amino acids (from the small intestine)
· Carbon Dioxide (from the cells to the lungs)
· Urea (from the liver to the kidney)
· Hormones
· Antibodies and antitoxins
Used in blood clotting to stop bleeding
They make a net at the side of a cut, this net traps red…read more

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Megan Nolan
the body, it has its own supply of blood fed through coronary vessels on the outside of the heart.…read more


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