Assertion: vein's valve | /r/HasProperty | weak
Facets:
Source sentences:
text: If these valves are weak or damaged, blood can flow backward and pool in the vein, causing the veins to stretch or twist.
text: If the valves are weak or damaged, blood can back up and pool in your veins.
text: If the valves are weak or damaged, blood can back up and pool in your veins.