The role of the digestive system is to break down food so that nutrients can be absorbed by the body. Like the respiratory system, it benefits from having a large surface area and close contact with the circulatory system.

Digestive System Worksheet - http://science-class.net/Lessons/Anatomy/Digestive/The%20Digestive%20System.pdf

DigestiveSystem.jpg
Digestive system

Mouth (teeth, tongue and salivary glands)
Oesophagus
Stomach
Small intestine
Large intestine
Rectum and anus