In the heart, we will go through the left atrium and then the left ventricle. Then, we go through the aorta where the arteries take us to the rest of the body.
Oh look! There is a white blood cell. White blood cells help to fight off disease and infections so they are very helpful.
Sometimes, things go wrong in the circulatory system. For example, there is a blood disorder called anemia. Anemia is when there aren't enough red blood cells. Since blood cells carry oxygen, anemia causes shortness of breath and fatigue. Anemia is definitely something you don't want.