Transports oxygen from the lungs to the rest of
the body.
There is no nucleus so that they can be filled with
haemoglobin, the substance that binds with oxygen.
They have a biconcave shape, giving them a large surface
area for the exchange of oxygen.
Plasma
The liquid that carries nutrients (e.g. glucose and amino acids),
antibodies, hormones and waste (e.g. carbon dioxide and urea).
Platelets
Small fragments of cells that help the blood to clot
at the site of a wound
White Blood Cells
Help to fight infection by protecting the body
against attack from microorganisms
The Circulatory System
Humans have a double circulatory system - two
circuits joined together.
The first circuit pumps deoxygenated blood to the lungs, to
take in oxygen. The blood then returns to the heart.
The second circuit pumps oxygenated blood around the body. The blood gives up it's oxygen at the body
cells and the deoxygenated blood returns to the heart to be pumped around the first circuit.