How are the blood vessels are connected to one another?

Lets start with the heart. Blood enters the left atrium, then into the left ventricle. It gets pumped out of the aorta to the rest of your body. The aorta branches off to smaller arteries which branch off into even smaller artirioles until finally they are so small that they become a capillary. In the capillary bed oxygenated blood looses its oxygen to the surrounding tissue and becomes deoxygenated within the capillary bed. the capillarys begin growing larger into veins until they make their way back to largest vein the Vena Cava. The vena cava empties its blood into the right atrium, then to the right ventricle where it gets pumped into the pulmonary artery that leads to the lungs, the pulmonary artiery branches off into smaller arteries in the lungs and similar to the capillary bed the blood gets reoxygenated in the avioli of the lung. Once reoxygenated the veins again start becoming larger as they make their way out of the lungs until they empy into the pulmonary vein which empties into the left atrium where the process starts all over again.