Assertion: vein's valve | /r/CapableOf | prevent blood
Facets:
Source sentences:
text: These valves prevent blood from flowing backward.
text: For example, a capillary is microscopically thin to allow gases to exchange, the arteries are tough and flexible to cope with high pressure blood flow and the veins contain valves to prevent the blood from travelling backwards when at low pressure.
text: Once blood is pumped out of the left ventricle and into the aorta, the aortic semilunar valve (or aortic valve) closes, preventing blood from flowing backward into the left ventricle.