Library of Congress
Loc: Everyday Mysteries: What Is the Strongest Muscle?
There are a variety of ways one can look at what might be the strongest muscle in the body. This site defines the various types of muscles and goes on to explain which would be considered the strongest.
Science Museum of Minnesota
Lesson Plan: Go With the Flow
In this effective site, students will name the parts of the heart and trace the flow of blood through the body. Contains related links.