Know the Terrain...

          The human heart is truly an amazing organ. From the time we are born, the heart may beat around 100,000 times per day. Most of us dont put a great deal of thought into that and we really don't need to. We grow up knowing almost nothing about this muscle that keeps our blood circulating day after day. Even when we begin to learn about the heart in school, we do not realize that we are only scratching the surface of a very complex subject. In fact, many of us go through our entire lives without giving this increadible muscle much thought at all. It is, it seems, only when something different happens with the heart, that we actually sit up and take notice.

          The heart is a muscular structure that lies roughly in the center of the chest. The muscle tissue of the heart surrounds four chamber, two on the top and two on the bottom. The top chambers are called atria and the bottom chambers are known as the ventricles. The atria are smaller than the ventricles and recieve blood as it returns from the body or the lungs. The ventricles are larger as they are responsible for most of the pumping action that keeps the blood circulating in your body.

          As blood circulates through your body, it travels through a network of arteries and veins. The term arteries refers to vessels that transport blood away from the heart. As the circulating blood travels out into the body, it passes into smaller and smaller arteries until it reaches the capillary beds where most of the oxygen and nutrients carried in the blood are delivered to the different cells of the body. After the blood deposites the nourishment and oxygen, it picks up waste products and carbon dioxide (CO2). The waste products will eventually be filtered out by the liver and the CO2 will be taken back to the right side of the heart and delivered to the lungs where it will be exchanged for oxygen.

          Blood flow returns to the heart after passing through the body by way of two large veins. The superior vena cava (SVC) provides blood return from the upper portion of the body while blood flowing from the lower portion of the body enters the heart through the inferior vena cava (IVC). Both of the vena cava connect to the right atrium.