National Cancer Institute at the National Institutes of Health
Seer Training Modules: Introduction to the Digestive System
Self-guided learning activity where students learn about the structure and function of the human digestive system. There is a short quiz at the end of the lesson to check for understanding.
Other
Cartage.org: The Excretory System
This comprehensive resource examines the human excretory system, kidney function, nitrogen wastes, water and salt balance, and more.