How do the heart valves work?

Intermountain Healthcare
Administration
Four heart valves control the flow of blood through the heart. They act as one-way doors, opening to let blood exit or enter a chamber, then closing to keep blood from flowing backward.
  • The tricuspid valve controls blood flow from the right atrium to the right ventricle.
  • The pulmonary (pulmonic) valve controls blood flow from the right ventricle into the pulmonary artery that delivers blood to the lungs.
  • The mitral valve controls blood flow from the left atrium to the left ventricle.
  • The aortic valve controls blood flow from the left ventricle into the aorta.
The heart consists of four chambers, two atria (upper chambers) and two ventricles (lower chambers). There is a valve through which blood passes before leaving each chamber of the heart. The valves prevent the backward flow of blood.

As the heart muscle contracts and relaxes, the valves open and shut, letting blood flow into the ventricles and atria at alternate times. The following is a step-by-step illustration of how the valves function normally in the left ventricle:
  • After the left ventricle contracts, the aortic valve closes and the mitral valve opens, to allow blood to flow from the left atrium into the left ventricle.
  • As the left atrium contracts, more blood flows into the left ventricle.
  • When the left ventricle contracts, the mitral valve closes and the aortic valve opens, so blood flows into the aorta.
Eastside Medical Center
Administration
The heart has two upper chambers called the right and left atria and two lower chambers called the right and left ventricles. On the right side of the heart, blood lacking oxygen returns from the body into the right atrium. The tricuspid valve connects the right atrium to the right ventricle and opens allowing blood to flow from the right atrium to the right ventricle when the heart is not contracting. When the heart contracts, the tricuspid valve closes preventing blood from flowing backwards from the right ventricle into the right atrium. Then the right ventricle ejects blood across the pulmonic valve into the pulmonary arteries and eventually the lungs. The pulmonic valve closes preventing blood from flowing backwards from the lungs into the right ventricle. After blood passes through the lungs, picking up oxygen, it arrives in the left atrium and crosses the mitral valve into the left ventricle. When the heart contracts, the mitral valve closes, preventing blood from flowing backwards from the left ventricle to the left atrium. The left ventricle ejects blood across the aortic valve into the aorta and the rest of the body. Then the aortic valve closes, preventing blood from flowing backwards from the body into the left ventricle. Of course in reality, blood flows to both sides of the heart at the same time, with heart valves on both sides opening and closing at the same time.
Piedmont Heart Institute
Administration
At the start of each heartbeat, blood returning from the body and the lungs fills the heart's two upper chambers. The mitral and tricuspid valves are located at the bottom of these chambers. As the blood builds up in the upper chambers, these valves open to allow blood to flow into the lower chambers of your heart.
After a brief delay, as the lower chambers begin to contract, the mitral and tricuspid valves shut tightly. This stops blood from flowing backward.
As the lower chambers contract, they pump blood through the pulmonary and aortic valves. The pulmonary valve opens to allow blood to flow from the right lower chamber into the pulmonary artery. This artery carries blood to the lungs to get oxygen.
At the same time, the aortic valve opens to allow blood to flow from the left lower chamber into the aorta. This aorta carries oxygen-rich blood to the body. As the contraction ends, the pulmonary and aortic valves shut tightly. This stops blood from flowing backward into the lower chambers.
This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.

Continue Learning about Heart and Circulatory System

Heart and Circulatory System

Heart and Circulatory System

Your circulatory system is made up of your heart and three main types of blood vessels -- arteries, veins and capillaries. Your heart is at the center of the system, acting as a pump to distribute nutrient- and oxygen-rich blood t...

hrough your body; it then takes away carbon dioxide and other waste your body doesn't need. Signs of poor circulation include cold hands and feet, numbness, dizziness, migraines, varicose veins and pain in your feet or legs. Untreated, poor circulation can lead to stroke, high blood pressure, kidney damage and other diseases. Learn more about your heart and circulatory system with expert advice from Sharecare.
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