Blood is the red liquid that your heart pumps all around your body. It flows through tubes called blood vessels. Blood is made up of platelets, red blood cells and white blood cells; all floating in a yellowish liquid called plasma.

Red blood cells carry oxygen from the lungs to every cell in the body. A normal red blood cell is shaped like a disk with a concave top and bottom. Because of its flexible outer layer, a red blood cell is able to bend and twist to pass through the tiniest blood vessels (capillaries).

White blood cells make up only 1% of blood, but they are very important to the body’s immune system.