What do blood cells do?

There are three main types of blood cells – red blood cells, white blood cells, and platelets. Each plays a distinctly different role in the body. 

1. The red blood cells perform two main functions. They deliver oxygen from the lungs to all the peripheral body tissues and carry carbon dioxide away from the tissues and back to the lungs to be expelled as a waste product. 
2. The primary function of the white blood cells is to protect the body against bacterial, viral, parasitic, and fungal infection. There are several types of white blood cells, each of which plays a different role in protecting the body. 
3. Platelets are responsible for blood clotting. In case of a blood vessel rupture which causes bleeding, platelets group together forming clumps that plug the rupture and stop the bleeding.