From Tasting to Digesting

A free interactive lesson on the digestive system for Class 5 — how food travels through 9 metres of tubing from mouth to toilet. Learn about saliva, stomach acid, villi in the small intestine, and how nutrients enter the blood. Based on NCERT Class 5. Includes quiz.

Class 5 ScienceClass 5 / Grade 5Ages 7–10
Lesson
🍎 From Tasting to Digesting
Your body turns food into energy. How?🍎Mouth🫁Throat🫙Stomach🌀Small int.🚽Large int.Food travels ~9 metres before leaving your body.

When you eat a mango, your body doesn't just absorb it whole. It breaks it down step by step, extracting sugars, vitamins, and minerals, then passes the rest as waste. This journey from mouth to exit is about nine metres long and takes between one and three days.

Digestion starts in the mouth

Digestion begins the moment food enters your mouth. Your teeth break food into smaller pieces (mechanical digestion), while saliva starts the chemical process — it contains an enzyme called amylase that begins breaking down starch into simpler sugars. By the time you swallow, digestion is already underway.

Oesophagus and stomach

Food travels down the oesophagus (food pipe) via rhythmic muscle contractions called peristalsis — this is why you can swallow even standing on your head. In the stomach, powerful acid (pH 1–2) and enzymes break protein down further. The stomach churns food for 2–4 hours, turning it into a liquid called chyme.

Small intestine — where absorption happens

The small intestine is about 6–7 metres long and is where most digestion and virtually all nutrient absorption occurs. Its inner wall is covered in tiny finger-like projections called villi, and each villus is covered in even smaller microvilli — together they increase the surface area to the size of a tennis court, maximising absorption.

Nutrients — glucose, amino acids, fatty acids — pass through the villi walls into the bloodstream and are carried to cells throughout the body.

Large intestine and beyond

The large intestine (about 1.5 metres) absorbs water and salts from the remaining material. Billions of bacteria live here and help break down some remaining material and produce vitamins like B12 and K. What cannot be absorbed becomes faeces and is stored in the rectum until elimination.

The complete journey from eating to elimination takes 24–72 hours depending on what you eat.

Frequently asked questions

How long is the human digestive system?

The entire digestive tract from mouth to anus is about 9 metres long — with the small intestine making up 6–7 metres and the large intestine about 1.5 metres.

What does the small intestine do?

The small intestine is where most digestion and almost all nutrient absorption happen. Its inner walls are covered in villi — tiny projections that increase surface area to absorb glucose, amino acids, and fatty acids into the bloodstream.

Why doesn't the stomach digest itself?

The stomach lining produces a thick layer of mucus that protects it from the acid it secretes. The lining also replaces itself completely every few days. When this protection breaks down, it causes ulcers.

What is peristalsis?

Peristalsis is the wave-like muscle contractions that push food through the digestive tract. It allows food to move through the oesophagus, stomach, and intestines — and is why you can swallow even if you're upside down.

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