[MUSIC PLAYING] Learning blood flow through the heart is one of the core objectives in the cardiovascular system and can be useful in identifying structures of a dissected heart. In this video, you will learn blood flow through the heart, identify the four chambers of the heart, identify major blood vessels of the heart, and identify the four valves associated with the heart. Before we begin, recall that arteries carry blood away from the heart, while veins are responsible for returning blood to the heart. In models and diagrams, most arteries will be red representing oxygenated blood, while most veins are blue, representing deoxygenated blood. But do not use color to determine if that vessel is an artery or a vein. The superior and inferior vena cava are two large veins responsible for returning blood to the heart from the systemic circuit. Deoxygenated blood enters the right atrium, passes through the tricuspid valve, and enters the right ventricle. From the right ventricle, the blood moves upward through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk branches into left and right pulmonary arteries, which deliver the oxygen-poor blood to the lungs. Notice, these are the only blue arteries on the model. At the lungs, the blood picks up oxygen and returns to the heart through the pulmonary veins. Note that the pulmonary veins are red on the model. The pulmonary veins empty into the left atrium. From the left atrium, blood passes through the bicuspid, or mitral, valve and enters the left ventricle, then passes through the aortic semilunar valve into the aorta. The aorta will deliver the oxygenated blood to the systemic circuit. Learning blood flow using the model can be very beneficial when attempting to identify the vessels, valves, and chambers on a real heart. The hearts used for dissection are not nearly as clean and neat as the model. Begin by getting your bearings. The front of the heart is typically the cleaner side. The apex will point down and to the left. If you're touching the apex, you're touching the left ventricle. For the identification of vessels, valves, and chambers, it will be useful to have a blood flow chart printed out for reference. Once you have cut the heart into anterior and posterior sections, you can easily identify the structures using the blood flow pathway. First, we will find the left ventricle. Remember, the apex points left, so if you touch the apex, you are touching the left ventricle. In addition, the left ventricle has a much thicker myocardium than the right. From the left ventricle, you can work backward to locate the bicuspid valve and left atrium. Feel inside the left atrium for an opening. That opening will be the remnants of the pulmonary veins. Remember, the pulmonary veins return blood to the left atrium. To find the aorta, go back to the left ventricle, and find an alternate pathway out. This would be the aortic semilunar valve and the aorta. The ventricle and the atrium opposite of these structures are the right atrium and right ventricle, making this the tricuspid valve. To find the vena cava, which empty into the right atrium, feel for an opening in the right atrium. Once you find it, you should be able to run your finger or probe through it and find both ends to locate the vena cava. Finally, you can find the pulmonary trunk by tracing your way through the right ventricle. You likely will not see the pulmonary semilunar valve, although you may be able to feel it. The pulmonary trunk branches into left and right pulmonary arteries, which may or may not be present.