How do blood and blood vessels work?

Blood is a liquid tissue that contains plasma, red blood cells, white blood cells, and platelets. Plasma is a clear liquid that mades up 56% of blood. It is made up of water and protein, and it transports nutrients and vitamins from the digested food you eat.

The red blood cells, white blood cells, and platelets are suspended in the plasma. Red blood cells make up 40% of blood, and they transport oxygen and carbon dioxide. White blood cells and platelets make up 4% of blood. The white blood cells fight off germs (that enter the body), and they break down dead cells. The platelets clot to each other at an open wound or just a wound and form a scab to stop the bleeding. They also prevent blood from flowing through the blood vessels.