Physiology
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Boundless Anatomy and Physiology
Cardiovascular System: The Heart
Circulation and Heart Valves
Physiology Textbooks Boundless Anatomy and Physiology Cardiovascular System: The Heart Circulation and Heart Valves
Physiology Textbooks Boundless Anatomy and Physiology Cardiovascular System: The Heart
Physiology Textbooks Boundless Anatomy and Physiology
Physiology Textbooks
Physiology
Concept Version 9
Created by Boundless

Operation of Semilunar Valves

The semilunar valves allow blood to be pumped into the major arteries, but prevent backflow of blood from the arteries into the ventricles.

Learning Objective

  • Describe the operation of the semilunar valves, the aortic and pulmonary valves


Key Points

    • The semilunar valves act to prevent backflow of blood from the arteries to the ventricles during ventricular diastole, and to help maintain pressure on the major arteries.
    • The aortic semilunar valve separates the left ventricle from the opening of the aorta.
    • The aortic and pulmonary valves are semilunar valves which separate the ventricles from the aorta and pulmonary artery, respectively.

Terms

  • aortic valve

    The tricuspid valve that lies between the left ventricle and the aorta.

  • pulmonary valve

    The semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps.

  • Semilunar valves

    Located at the base of both the trunk of the pulmonary artery and the aorta, and prevent backflow of blood from the arteries into the ventricles.


Full Text

The semilunar valves are located at the connection between the pulmonary artery and the right ventricle, and the aorta and the left ventricle. These valves allow blood to be pumped into the arteries, but prevent backflow of blood from the arteries into the ventricles. These valves do not have chordae tendineae, and are more similar to valves in veins than to atrioventricular valves.

The semilunar valves act in concert with the atrioventricular valves to direct blood flow in the heart. When the atrioventricular valves are open, the semi lunar valves are shut and blood is forced into the ventricles. When the atrioventricular valves shut, the semilunar valves open, forcing blood into the aorta and pulmonary artery.

The Aortic Valve

The aortic valve separates the left ventricle from the aorta and has three cusps . During ventricular systole, pressure rises in the left ventricle. When the pressure in the left ventricle exceeds the pressure in the aorta, the aortic valve opens, and blood flows from the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle drops rapidly, and the aortic pressure forces the aortic valve to close.

Heart viewed from above

This anterior view of the heart indicates the semilunar valves, the aortic and pulmonary valves.

The Pulmonary Valve

The pulmonary valve (sometimes referred to as the pulmonic valve), which also has three cusps, separates the right ventricle from the pulmonary artery. Similar to the aortic valve, the pulmonary valve opens in ventricular systole, when the pressure in the right ventricle exceeds the pressure in the pulmonary artery. When ventricular systole ends, pressure in the right ventricle drops rapidly, and the pressure in the pulmonary artery forces the pulmonary valve to close.

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