The Digestive System — Interactive Diagram

TL;DR: Trace food on its journey from mouth to absorption, and see where digestion happens at each stop.

The Digestive System: Trace food on its journey from mouth to absorption, and see where digestion happens at each stop.

Why it matters: The path of food and where nutrients are absorbed is core to biology — and helps you understand healthy eating and common digestion problems.

The Digestive System — Step by Step

1. Digestion starts in the MOUTH: teeth break food down and saliva begins digesting starch. Food then travels down the food pipe (oesophagus).
2. In the STOMACH, strong acids and enzymes churn the food into a paste and digest proteins.
3. The SMALL INTESTINE is where most digestion finishes and nutrients are ABSORBED into the blood through its long, folded walls.
4. Undigested waste passes to the LARGE INTESTINE, where water is absorbed, and the rest leaves the body. Journey complete!

Quick Notes — the Exam Crux

• Digestion begins in the mouth: teeth grind food while saliva's amylase breaks starch into sugar.
• The oesophagus pushes food to the stomach by peristalsis (wave-like muscle movements).
• Stomach: gastric juice has HCl (kills germs, activates enzymes) and pepsin (digests protein).
• Small intestine: the main site of BOTH digestion and absorption; bile (from liver) and pancreatic juice act here.
• Villi — tiny finger-like folds — give a huge surface area to absorb nutrients into the blood.
• The large intestine absorbs water; undigested waste leaves through the rectum and anus.

Remember It (Memory Trick)

Food's path: Mouth → Oesophagus → Stomach → Small intestine → Large intestine. Remember the small intestine is where most absorption happens — "small in size, big in job."

Real-Life Example

Chew a roti slowly and it starts tasting sweet — that is the saliva enzyme (amylase) breaking starch into sugar right in your mouth, the very first step of digestion.

Test Yourself

Where is most of the food absorbed into the blood?

In the small intestine, through the villi.

What are the two main jobs of hydrochloric acid in the stomach?

It kills germs in the food and makes the medium acidic so the enzyme pepsin can work.

What is peristalsis?

The wave-like muscular contractions that push food along the alimentary canal.

📖 Read the full explanation of The Digestive System →

More Visual Lessons

• Photosynthesis
• The Human Heart & Blood Flow
• The Respiratory System
• Plant Cell vs Animal Cell
• Food Chain & Energy Flow
• Reflex Action

🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →