Let’s start by taking a tour of the anatomy of a heart. First we’ll examine an anterior external view of the heart. • The inferior vena cava is the vein that returns blood to the right atrium from the body regions inferior to the diaphragm. • The superior vena cava is the vein that returns blood to the right atrium from the body regions superior to the diaphragm. • The right atrium is the heart chamber that receives the oxygen-poor blood from the body. • The right ventricle is the heart chamber that pumps oxygen-poor blood to the lungs. • The pulmonary trunk receives oxygen-poor blood from the right ventricle; splits it into the right and left pulmonary arteries, which carry blood to the lungs. • The left ventricle is the heart chamber that pumps oxygen-rich blood to the body. • The aorta is the largest artery in the body. It receives oxygen-rich blood from the left ventricle. • The right coronary artery branches from the base of the aorta and supplies oxygenated blood to the right side of the heart. • The anterior interventricular artery is the branch of the left coronary artery that supplies oxygenated blood to the interventricular septum and the anterior walls of both ventricles. • The great cardiac vein is the lies along the anterior interventricular sulcus. It collects oxygen-poor blood from capillary beds of the myocardium. In this deep cut-away view, we can see more of the heart’s anatomy such as the pulmonary semilunar valve, which is the valve at the entrance to the pulmonary trunk. It prevents backflow into the right ventricle. The left pulmonary artery branches of off the pulmonary trunk to carry oxygen-poor blood to the left lung. The chordae tendineaeor “heart strings” anchor AV valve flaps to the papillary muscles. The papillary muscles are muscle bundles that project from the ventricular walls, connect to the AV valve flaps via chordae tendineae, and contract to hold AV valve flaps in the closed position. In this deep external view of the heart you find the aortic semilunar valve that is located at the entrance to the aorta and prevents backflow into the left ventricle. And here is the interventricular septum, an internal partition that separates the ventricles. When we look at the external right lateral view of the heart, we see many of the same parts. But this view also shows the right pulmonary veins that transport blood from the right lung to the left atrium; and the small cardiac vein, which runs along the heart’s right inferior margin and collects oxygen-poor blood from the capillary beds of the myocardium. Now let’s examine a right lateral cut-away view. Here you’ll find: The fossa ovalis, which is a shallow depression in the interatial septum marking the spot where an opening, the foramen ovale, existed in the fetal heart. The coronary sinus is a vessel that collects oxygen-poor blood from the cardiac veins; it empties the blood into the right atrium. The Tricuspid valve prevents blackflow into the right atrium when the right ventricle contracts. It has three flaps and is also known as the right atrioventricular (AV) valve. Here is an external posterior view of the heart that allows us to see the right pulmonary artery, which branches off of the pulmonary trunk to carry oxygen-poor blood to the right lung. Notice which parts of the heart can be seen in this posterior cut-away view. Now let’s look at a left lateral external view of the heart. And finally, last on our tour, is a left lateral cut-away view of the heart. The heart consists of two side-by-side pumps. The blood vessels are the "pipes" that carry blood throughout the body. In this animation, we see that the right atrium and right ventricle pump oxygen poor, carbon dioxide rich blood to the lungs. In the lungs, the blood receives oxygen, eliminates carbon dioxide, and travels back to the left atrium of the heart. From the left atrium, the oxygen rich, carbon dioxide poor blood is pumped out to the body by the left ventricle. When the body has depleted the bloods oxygen, the veins return the blood to the right atrium of the heart and the cycle continues This animation shows the same information that we saw on the previous page. Oxygen poor blood is pumped from the right side of the heart to the lungs. Here it receives oxygen and travels back to the heart. This pathway is a pulmonary circuit, so called because of the lungs. The pathway for the systemic circuit includes the entire body as the left side of the heart pumps oxygen rich blood out to the body's tissues and organs. After the blood's oxygen is depleted, it returns to the right side of the heart via the venous system.