Assertion: artery's muscle | /r/LocatedNear | vein
Facets:
Source sentences:
text: In these cases, the smooth muscles surrounding the veins become slack and the veins fill with the majority of the blood in the body, keeping blood away from the brain and causing unconsciousness.
text: Contraction of muscles surrounding veins help milk the blood through the venous valves and the valves direct the return of blood towards the heart.