Well, the cardiovascular system is used to actually bring and deliver the nutrients and electrolytes to the cells, the tissues and organs found inside our body and the blood. Our cardiovascular system also takes in the waste products produced by the cells and it brings those waste products to the proper organ of the body such as our skin and kidneys that are involved in excretion of those waste products. Now our cardiovascular system is said to be a closed cardiovascular system. It's a closed circuit. And what that basically means is all that blood travels throughout the blood vessels and it never actually leaves those blood vessels. Now that's not to say that the blood isn't actually filtered.