The heart consists of 4 chambers--2 atria (upper chambers) and 2 ventricles (lower chambers). Blood passes through a valve as it leaves each chamber of the heart. The valves prevent the backward flow ...

An illustration of a magnifying glass. An illustration of a magnifying glass.

Upcoming Movies and TV shows Rotten Tomatoes Podcast Media News + More ...

"Always makes me cry," one of his fans wrote in the Instagram comments of McGraw's post, while another one of his followers ...