THE HEART VALVES
Four valves regulate blood flow through the heart:
• Allows blood that has been returned from the body to flow from the right atrium to the right ventricle.
• Allows blood to flow from the right ventricle into the pulmonary arteries to the lungs for oxygenation.
• Also referred to as the Pulmonic valve.
• Allows oxygen-rich blood from the lungs to flow from the left atrium into the left ventricle.
• Allows oxygen-rich blood to pass from the left ventricle into the aorta, your body's largest artery, where it is delivered to the rest of your body.
Each valve has a set of leaflets or "flaps" (also called cusps). The mitral valve normally has two leaflets; the other valves each have three.
After circulating through the body, blood that has become dark and bluish because it is low in oxygen flows back to the heart through veins. It enters the right atrium, and then travels through the tricuspid valve into the right ventricle.
The right ventricle pumps the blood through the pulmonary valve (a low pressure valve), into the pulmonary artery, and on to the lungs where it meets fresh oxygen. After the blood is refreshed with oxygen, it is bright red. It then returns to the left atrium via the pulmonary veins. From the left atrium, it flows through the mitral valve to enter the left ventricle.
The left ventricle pumps the red, oxygen-rich blood out through the aortic valve into the aorta. The aorta takes blood to the body's general circulation. The blood pressure in the left ventricle is the same as the pressure measured in the arm.