The circulatory system is a network of flexible tubes through which blood flows as it carries oxygen and nutrients to all parts of the body. It includes the heart, lungs, arteries, arterioles (small arteries) and capillaries (minute blood vessels). It also includes venules (small veins) and veins, the blood vessels through which blood flows as it returns to the heart. If all these vessels were laid end-to-end, they would extend for about 60,000 miles--far enough to encircle the earth more than twice.
To learn more about how the heart accomplishes all this, you might want to explore the following web sites.
Map of the Human Heart
The Heart: An Online Exploration
Additional information about the anatomy of the heart can be found in our heatlh library