Understanding the Cardiovascular System

To understand your cardiovascular system, with its hardworking heart and complex support network of arteries, veins and capillaries, think of it as a delivery system of highways and roads that allow oxygen-rich blood to reach every cell of your body. The workhorse of this system is the heart, a big muscle that contracts and relaxes 80 times per minute. The heart contains four chambers separated by valves. Red blood cells, the "trucks" that load and unload oxygen, carbon dioxide and toxins, enter the first chamber/holding area, known as the right atrium. They then pass through a gate called the tricuspid valve into a second holding area, the right ventricle. From here, the red blood cells travel to the lungs to dump their garbage of carbon dioxide and other gaseous toxins and load up the with oxygen molecules. Next, the oxygenated red blood cells enter the third holding area, the left atrium, and pass through the second major gate, the mitral valve, also known as the bicuspid valve, into the last holding area, the left ventricle.

Loaded with oxygen, the "trucks" leave the heart via arteries, which are like big highways. Arteries can accommodate a large flow of red blood cells, and help to propel them along. As arteries lead farther away from the heart, they decrease in size like highways turning into single lane back roads. Smaller arteries are called arterioles and the tiniest blood vessels are capillaries. Along these roadways, the red blood cells deliver their oxygen and pick up carbon dioxide, a waste product. Then they head back to the heart and lungs on ever-widening roadways called venules. These roadways continue to widen until they become highways again or what are called veins.