Alimentary Canal Diagram IGCSE Biology 0610

Alimentary Canal Diagram: Digestive System Overview

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

Key diagram

The alimentary canal runs from mouth to anus: mouth, oesophagus, stomach, duodenum, ileum, colon, rectum and anus. The liver and pancreas are associated organs that produce secretions delivered to the duodenum.

The alimentary canal diagram is the foundation of every digestion question. Students must be able to label each organ, state the enzyme(s) it produces or contains, and describe what happens to food at each stage.

Drawing the complete pathway

Draw the digestive tract as a continuous tube. Start with the mouth (containing teeth and the tongue). The oesophagus is a muscular tube connecting the mouth to the stomach: draw it as a narrow tube leading down. The stomach is a J-shaped muscular sac. Below the stomach, draw the small intestine, divided into the duodenum (short, first section) and the ileum (long, coiled section). The large intestine follows, drawn as a wider tube forming the colon, leading to the rectum and ending at the anus.

Associated organs

Draw the liver as a large organ above and to the right of the stomach, with the gall bladder underneath it. The gall bladder stores bile, which is released into the duodenum. Draw the pancreas behind the stomach, with a duct leading to the duodenum. The pancreas produces pancreatic juice containing amylase, protease (trypsin) and lipase.

Digestion at each stage

In the mouth, salivary amylase begins starch digestion and teeth mechanically break down food. The stomach produces hydrochloric acid (kills bacteria, provides acidic pH) and protease (pepsin). In the duodenum, bile emulsifies fats and pancreatic enzymes continue digestion. In the ileum, digestion is completed and the products are absorbed through villi into the blood and lymph.

The colon absorbs water from undigested food. The rectum stores faeces before they are expelled through the anus (egestion).

Peristalsis

Food is moved along the alimentary canal by peristalsis: rhythmic waves of muscular contraction behind the food bolus. The circular and longitudinal muscles in the gut wall contract alternately to push food along. Include arrows on the diagram showing the direction of food movement.

Label checklist

Check these labels are present and correctly positioned before finishing your drawing.

✓ Mouth
✓ Oesophagus
✓ Stomach
✓ Duodenum
✓ Ileum
✓ Colon (large intestine)
✓ Rectum
✓ Anus
✓ Liver
✓ Gall bladder
✓ Pancreas

Try a diagram question (2 marks)

On the diagram of the alimentary canal, label the organ where: (a) protein digestion begins, (b) most absorption of digested food occurs. [2]

Show the answer and marking guidance

(a) Stomach: protease (pepsin) begins protein digestion in acidic conditions.
(b) Ileum (small intestine): villi provide a large surface area for absorption.

Original Cambridge-style practice written for this site.

Common diagram mistakes

Check these against your own drawing before moving on.

Labelling the whole small intestine as the duodenum: the duodenum is only the first short section.
Forgetting the liver and pancreas: they are not part of the tube but must be labelled.
Placing the pancreas above the stomach instead of behind it.
Confusing egestion (removal of undigested food) with excretion (removal of metabolic waste).