In the human alimentary canal, food passes from mouth through oesophagus, stomach, small intestine, large intestine, rectum and anus. Peristalsis moves material along the tract. The stomach mixes food with acidic secretions and begins substantial protein digestion. Most digestion and nutrient absorption occur in the small intestine; the large intestine reabsorbs water and helps form faeces.
Accessory organs supply substances without food passing through them. The pancreas releases digestive enzymes into the small intestine. The liver makes bile, and the gallbladder stores and concentrates it before release. Bile emulsifies fats; it is not an enzyme. Villi line the small intestine and provide an extensive surface for nutrient absorption.
Example 1
Complete the route: mouth → oesophagus → ? → small intestine.
The missing organ is the stomach.
Example 2
Food enters the small intestine, but not the pancreas. How does the pancreas assist digestion?
It supplies digestive enzymes through a duct into the small intestine.
Watch out: Food follows the alimentary canal. The liver and pancreas contribute secretions through ducts.