Assertion: giraffe's valve | /r/CapableOf | prevent blood
Facets:
Source sentences:
text: The jugular veins contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atrium while the head is lowered.
text: The animal has a specialized cardiovascular system that keeps blood moving adequately to the brain and heart when it moves its neck and head around, ensuring that bending down to take a sip of water won't cause a possibly lethal head rush [source: Dagg and Foster]. Giraffes' blood vessels are equipped with valves that prevent blood from backtracking due to gravity [source: