Blood flow through the heart

Understanding the flow of blood through the heart is critical for understanding the overall functions of the heart and the way that changes in electrical activity affect peripheral blood flow. It's also important to remember that right- and left-sided heart events occur simultaneously. Deoxygenated blood from the body returns to the heart through the inferior vena cava, superior vena cava, and coronary sinus and empties into the right atrium. The increasing volume of blood in the right atrium raises the pressure in that chamber above the pressure in the right ventricle. Then the tricuspid valve opens, allowing blood to flow into the right ventricle. The right ventricle pumps blood through the pulmonic valve into the pulmonary arteries and lungs, where oxygen is picked up and excess carbon P.7dioxide is released. From the lungs, the oxygenated blood flows through the pulmonary veins and into the left atrium. This completes a circuit called pulmonic circulation. As the volume of blood in the left atrium increases, the pressure in the left atrium exceeds the pressure in the left ventricle. The mitral valve opens, allowing blood to flow into the left ventricle. The ventricle contracts and ejects the blood through the aortic valve into the aorta. The blood is distributed throughout the body, releasing oxygen to the cells and picking up carbon dioxide. Blood then returns to the right atrium through the veins, completing a circuit called systemic circulation. Coronary blood supply Blood flow through the heart Like the brain and all other organs, the heart needs an adequate supply of oxygenated blood to survive. The main coronary arteries lie on the surface of the heart, with smaller arterial branches penetrating the surface into the cardiac muscle mass. The heart receives its blood supply almost entirely through these arteries. In fact, only a small percentage of the heart's endocardial surface can obtain sufficient amounts of nutrition directly from the blood in the cardiac chambers. (See Vessels that supply the heart, Blood flow through the heart .) Understanding coronary blood flow can help you provide better care to a patient with coronary artery disease because you'll be able to predict which areas of the heart would be affected by a narrowing or occlusion of a particular coronary artery.