How do valves in the heart and blood vessels work?

[sameeralord]

Hello everyone,

How do valves in the body basically work. I can understand how blood flowing on either direction can close or open valves depending on the type of valve. But someone told me it is the elastic recoil of the veins that closes the valve. I thought it would blood that was going back that closed the valve. Also in the heart does the contraction of right ventricle close the mitral valve or the blood going back from the ventricle that closes the valve.

Also while we are at it. I read that aortic valve closes before pulmonary valve in a textbook. The reason was this in the textbook

"Aortic valve closes before the closure of pulmonary valve because of the lower impedance of the pulmonary vasculature"

I don't understand what they are saying could anyone explain. Thanks

 

[Drakkith]

Also in the heart does the contraction of right ventricle close the mitral valve or the blood going back from the ventricle that closes the valve.

From wikipedia:

When the left ventricle contracts, the pressure in the ventricle forces the valve to close, while the tendons keep the leaflets coapting together and prevent the valve from opening in the wrong direction (thus preventing blood to flow back to the left atrium).

Looks like it's simply a pressure difference that causes closure and opening.