There is not a set place where the pathway of blood begins, but a lot of people like to say that the process begins in the right atrium. From the right artium, blood flows through the Tricuspid Valve into the Right Ventricle. Then it goes through the Pulmonary Valve up into the Pulmonary Trunk and out the Pulmonary Arteries into the lunges. From the lungs, the bllod enters back into the heart through Pulmonary Veins and is dumped into the Left Atrium. After that, it flows through the Mitral Valve and into the Left Ventricle. From the Left Ventricle, blood flows through the Aortic Valve, into the Ascending Aorta,  and to the Aortic Arch. The Aortic Arch consists of the Brachiocephalic Trunk, the Left Common Carotid Artery, and the Left Subclavian Artery. Blood will either flow out one of these arteries to the rest of the body, or it will continue down the Descending Aorta. Then, it will go from arteries, to arterioles, to capillaries, to venuoles, to veins that will eventually lead back to the Superior or Inferior Vena Cava. Lastly, the blood will dump from the Superior or Inferior Vena Cava back into the Right Atrium, and the process will start over.

To better understand the pathway of blood, here are a few definitions you will need to know:
            -Arteries: large blood vessels that transport blood away from the heart
            -Arterioles: medium sized blood vessels that transport blood away from the heart
            -Capillaries: smallest blood vessels
            -Venuoles: medium sized blood vessels that transport blood to the heart
            -Veins: large blood vessels that transport blood to the heart