Assertion: circulatory system's vein | /r/MadeOf | many one-way valves
Facets:
Source sentences:
text: To facilitate the movement of blood, some veins contain many one-way valves that prevent blood from flowing away from the heart.
text: To facilitate the movement of blood, some veins contain many one-way valves that prevent blood from flowing away from the heart.
text: To facilitate the movement of blood, some veins contain many one-way valves that prevent blood from flowing away from the heart.