The determinant of whether heart valves are open or closed is the pressure difference across them.

Question

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The pressure difference across heart valves determines whether they are open or closed. For example, in the case of the mitral valve, the pressure in the left atrium must be greater than the pressure in the left ventricle for the valve to open and allow blood to flow from the atrium to the ventricle. Similarly, the pressure in the aorta must be greater than the pressure in the left ventricle for the aortic valve to open and allow blood to be ejected from the heart.

The Determinant of Whether Heart Valves Are Open or Closed