The circulatory system includes the heart, arteries, veins, and blood. Its function is to move oxygen and nutrients to organs,
tissues, and cells. It also moves hormones and other substances throughout the body. The arteries carry blood away from the
heart. The veins carry blood back to the heart. The system of blood vessels is often thought of as a tree, with the “trunk,” or
main artery (aorta), branching into the large arteries, which branch into smaller and smaller vessels. This system is sometimes
called the <u>cardiovascular or vascular system</u>.