circulatory system

The Circulatory System is the main transportation and cooling system for the body. The Red Blood Cells act like billions of little UPS trucks carrying all sorts of packages that are needed by all the cells in the body. Instead of UPS, I'll call them RBC's. RBC's carry oxygen and nutrients to the cells. Every cell in the body requires oxygen to remain alive. Besides RBC's, there are also White Blood Cells moving in the circulatory system traffic. White Blood Cells are the paramedics, police and street cleaners of the circulatory system. Anytime we have a cold, a cut, or an infection the WBC's go to work.
The highway system of the Circulatory System consists off a lot of one way streets. The superhighways of the circulatory system are the veins and arteries. Veins are used to carry blood *to* the heart. Arteries carry blood *away* from the heart. Most of the time, blood in the veins is blood where most of the oxygen and nutrients have already been delivered to the cells. This blood is called deoxygenated and is very *dark* red. Most of the time blood in the arteries is loaded with oxygen and nutrients and the color is very *bright* red. There is one artery that carries deoxygenated blood and there are some veins that carry oxygenated blood. To get to the bottom of this little mystery we need to talk about the Heart and Lungs.