Assertion: vein's valve | /r/CapableOf | serve to direct the flow of blood
Facets:
value: to the heart
type: TRANSITIVE-OBJECT
value: in an upward direction
type: TRANSITIVE-OBJECT
Source sentences:
text: These valves, formed by semilunar folds in the tunica intima, are present in pairs and serve to direct the flow of blood to the heart, particularly in an upward direction.