Digestion and Teeth (KS2 Science)

SC5Digestion and Teeth

From plate to energy.

Digestion breaks food down so the body can absorb it; teeth do the first mechanical work.

The journey of food.

👄 mouth→🫃 stomach→➰ small intestine→🚽 large intestine

food is broken down and nutrients absorbed along the way

Teeth cut and grind; the stomach and intestines break food down chemically.

Learn the Journey

1Mouth: teeth and saliva.

Teeth cut and grind food; saliva moistens it and begins breaking it down. Swallowed food travels down to the stomach.

chew + saliva

2Stomach and small intestine.

The stomach churns food with juices; the small intestine absorbs the useful nutrients into the blood.

break down + absorb

3Teeth types do different jobs.

Incisors (front) cut, canines (pointed) tear, molars (back) grind. Humans have all three because we’re omnivores.

incisor · canine · molar

💡 Key IdeaCarnivores have big canines for tearing meat; herbivores have broad molars for grinding plants. An animal's teeth reveal its diet.

Worked Example

Why do we brush teeth, and what causes tooth decay?

Cause

bacteria in the mouth feed on sugar and make acid

→

Effect

acid dissolves the hard enamel → decay (holes)

→

✓ Prevention

brushing removes bacteria & sugar; less sugary food helps

Watch Out! Common Mistakes

‘Sugar directly rots teeth.’

Bacteria are the culprit! Sugar feeds mouth bacteria, which produce the acid that dissolves enamel. That’s why brushing (removing bacteria) protects teeth.

‘The stomach does all digestion.’

It’s a team! Digestion starts in the mouth and most nutrients are absorbed in the small intestine, not the stomach.

Confusing the intestines.

Different jobs! The small intestine absorbs nutrients; the large intestine absorbs water and forms waste.

⬇ Cheat Sheet

DIGESTION AND TEETH

Route: mouth → stomach → small intestine → large intestine.
Teeth: incisors cut, canines tear, molars grind.
Small intestine absorbs nutrients; large intestine absorbs water.
Decay: bacteria + sugar → acid → dissolves enamel.

Example: molars grind; small intestine absorbs the nutrients.

📖 Continue Your Journey

✓ SC1 Classifying Living Things ✓ SC2 Habitats and Adaptation ✓ SC3 Food Chains and Webs ✓ SC4 The Skeleton and Muscles SC5 Digestion and Teeth SC6 The Circulatory System SC7 Plants and Photosynthesis SC8 Life Cycles and Reproduction SC9 States of Matter and the Water Cycle SC10 Materials and Their Properties SC11 Reversible and Irreversible Changes SC12 Forces and Magnets SC13 Light and Shadows SC14 Sound SC15 Electricity and Circuits SC16 Earth and Space

→

Next Lesson: SC6 The Circulatory SystemThe heart, blood and a double loop.

📄 Free printable: Download the Digestion and Teeth cheat sheet (PDF) — keep it by your child's desk.

Quick summary

Food travels: mouth → stomach → small intestine → large intestine.
Incisors cut, canines tear, molars grind.
The small intestine absorbs nutrients; the large intestine absorbs water.
Decay: mouth bacteria feed on sugar and make acid that dissolves enamel.

Frequently asked questions

What are the three types of teeth?

Incisors at the front for cutting, pointed canines for tearing, and broad molars at the back for grinding — humans have all three as omnivores.

What actually causes tooth decay?

Bacteria in the mouth feed on sugar and produce acid, and that acid dissolves the tooth's hard enamel. Brushing removes the bacteria and sugar.

Where are nutrients absorbed?

Mainly in the small intestine, which passes them into the blood; the large intestine then absorbs water from what's left.

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