How does the blood move from one part of heart to next?
- The right atrium (upper right chamber)
- The right ventricle (lower right chamber)
- The left atrium (upper left chamber)
- The left ventricle (lower left chamber)
Blood flows into the heart through the superior vena cava (from the upper body) and the inferior vena cava (from the lower body) and enters the right atrium. From the right atrium, blood flows into the right ventricle. The right ventricle then pumps the blood to the lungs through the pulmonary artery. In the lungs, carbon dioxide is removed from the blood and oxygen is added. The oxygenated blood then returns to the heart via the pulmonary veins and enters the left atrium. From the left atrium, blood flows into the left ventricle. The left ventricle then pumps the blood out to the body through the aorta.
The movement of blood through the heart is controlled by a series of valves. These valves prevent blood from flowing backward. The valves include:
- The tricuspid valve (between the right atrium and the right ventricle)
- The pulmonary valve (between the right ventricle and the pulmonary artery)
- The mitral valve (between the left atrium and the left ventricle)
- The aortic valve (between the left ventricle and the aorta)
The heart rate is controlled by a group of cells in the right atrium called the sinoatrial node (SA node). The SA node sends out electrical impulses that cause the heart to contract. The electrical impulses then travel through the atrioventricular node (AV node), which is located between the atria and the ventricles. The AV node delays the electrical impulses slightly, which allows the ventricles to fill with blood before they contract. The electrical impulses then travel down the bundle of His and into the Purkinje fibers, which cause the ventricles to contract.
The heart rate can be increased or decreased by the nervous system. When the body is at rest, the heart rate is slow. When the body is exercising, the heart rate increases to pump more blood to the muscles.