Do right and left seem backward? That's because you're looking at an illustration of somebody else's heart. To think about how your own heart works, imagine wearing this illustration on your chest.

Leonardo Da Vinci was one of the first people to draw detailed sketches of human anatomy. His drawings showed that he noticed networks of muscle fibers on the inside of the heart. Da Vinci thought ...

In the Step Thru below, see the complicated path the blood takes as it moves in and out of the heart. Do right and left seem backward? That's because you're looking at an illustration of somebody ...