Explains how the stomach, liver, intestines, and other organs and glands coordinate their activities. Also describes the biology behind the reproductive system.

Explains how skin, the largest organ in the body, encloses and protects muscles, bones, and internal tissues while playing a key role in keeping a person comfortable and healthy. Explores the differences between the three types of muscle fibers and their locations. Describes the arrangement of the bones and how their placement gives the body form and assists in movment.