Red blood cells absorb oxygen in the lungs and transport it to the organs and muscles.
White blood cells fight germs and infections in our body. They attack infected cells.
Platelets help to stop bleeding. When you have a cut that's bleeding, platelets stick to the edges of the cut and to each other. In this way, they cover the cut and form a scab, and this stops the bleeding.
The blood vessels are tubes that connect the heart to the rest of the body.
There are three types of blood vessels: arteries, veins and capillaries.
Arteries are large blood vessels that carry blood from your heart to the rest of your body. This blood is rich in oxygen and nutrients. As arteries get farther away from the heart they begin to branch and become smaller and smaller. The smallest branches are called capillaries.
Capillaries: this is where the oxygen of your blood is transferred to your tissues. In exchange, the wastes from your cells are transferred to the blood, including the carbon dioxide. Just beyond this area the capillaries begin to merge together and eventually form larger vessels called veins.
Veins lead back to the heart. As the vessels carry deoxygenated blood back to the heart, waste products are routed to other organs where they are removed.
The nutrients we eat and the oxygen we breathe are transported to our organs, bones, brain and muscles by the circulatory system.
The heart is an organ that acts like a pump.
It is divided into four chambers: the two upper are called the atria and the two lower are called ventricles.
When blood enters the heart, it's then pumped to the lungs. In the lungs, the red blood cells absorb oxygen. That oxygenated blood is pumped back into the heart. The heart then pumps the oxygenated blood around the body.
You can see it in this video:
