What are the functions of erythrocytes, leukocytes, platelets?

The blood is not homogeneous. It contains a liquid – plasma – and cells that perform a variety of functions. Erythrocytes are small, rounded red cells. They carry oxygen to the tissues. Every cell needs it for life. Erythrocytes carry carbon dioxide away from the tissues – in the lungs they exchange it for oxygen.
Platelets are clotting. Any wound and cut without platelets – the person will die.
There are many leukocytes in the blood. Some of them act on viruses, some on bacteria. But, in general, leukocytes are a person’s protection from infections.

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