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Primary Science · Year 4Chapter 5 · Teeth and the digestive system
Year 4 · Chapter 5

Teeth and the digestive system

By the end of this chapter you will be able to

  • Name the main parts of the digestive system, in the order that food passes through them
  • Say what the mouth, stomach, small intestine, large intestine and rectum do
  • Name the four types of teeth in an adult, and say what each one does
  • Count the teeth in an adult and a child, and compare them
  • Match an animal’s teeth to the food that it eats
  • Say simple ways to look after teeth and the digestive system

You should already know

  • The five food groups, and what animals need to stay alive (Year 3 Science, Chapter 5)
  • Skeletons, and how bones protect the body (Year 3 Science, Chapter 6)

Where this leads

  • Food chains, and how animals depend on the food they eat (Year 4 Science, Chapter 4)
  • The circulation of blood, and how the body uses nutrients (Year 6 Science)

National Curriculum for England, Key Stage 2 science, Year 4. Content: A1 describe the simple functions of the basic parts of the digestive system in humans, A2 identify the different types of teeth in humans and their simple functions.

Exercise P  Do you remember?

1
FWhich food group contains bread, rice and pasta? Write the words.
2
FWhich living things get their nutrition from what they eat? Write the word: animals or plants.
3
FName one of the five food groups. Write one group.
4
FWhich bones protect the heart and the lungs? Write the word.
5
FName one thing that every animal needs to stay alive. Write one thing.
5.1

The parts of the digestive system

Year 4
A1: describe the simple functions of the basic parts of the digestive system in humans
Video lesson: The parts of the digestive systemComing soon
Story. Ruby eats a sandwich at lunch. “Where does it go now?” she asks. Mr Patel says, “It goes on a long journey through your digestive system, from your mouth to the end of your body.”

The digestive system is a long tube, with several parts, that breaks down the food we eat. Food goes in at the mouth and comes out at the anus. The picture shows the parts in the order that food passes through them.

MouthOesophagusStomachSmall intestineLarge intestineRectumAnus
The digestive system from the mouth to the anus: the parts in order, with arrows showing the way food travels.

Key ideas

  • Food enters the digestive system at the mouth.
  • Food passes through the oesophagus and the stomach, then the small intestine and the large intestine.
  • Waste is stored in the rectum, and leaves the body at the anus.
  • The digestive system is one long tube, so food moves from one part to the next.
Worked example 5.1.1
Which part of the digestive system does food enter first? Write the name.

Method. Look at the top of the picture.

  1. Find the first part. Food goes in at the mouth, which is the first part.
    mouth
  2. Check the order. The mouth is at the top of the list in section 5.1.
    top
  3. Write the answer.
    Mouth

Check. Food is swallowed after it has been chewed in the mouth. ✓

Worked example 5.1.2
Which part of the digestive system comes straight after the stomach? Write the words: small intestine or large intestine.

Method. Find the stomach in the order.

  1. Find the stomach. The stomach is the third part in the order.
    third
  2. Read the next part. The part after the stomach is the small intestine.
    small intestine
  3. Write the answer.
    small intestine

Check. The large intestine comes after the small intestine. ✓

Worked example 5.1.3
Which part connects the mouth to the stomach? Write the word.

Method. Find the part between the mouth and the stomach.

  1. Find the part. The oesophagus lies between the mouth and the stomach.
    between
  2. Name it. The tube between the mouth and stomach is the oesophagus.
    oesophagus
  3. Write the answer.
    oesophagus

Check. The oesophagus is also called the gullet. ✓

Watch out

Watch out: the stomach is not the first part of the digestive system. Food is chewed in the mouth, and then passes down the oesophagus into the stomach.

Try it at home or school (with a grown-up). Look in a mirror with a grown-up, and find your mouth and your teeth. Then think about the order of the digestive system. Do not touch anything sharp, and wash your hands after eating.

Exam tip

Grown-up tip. Ask: “Where does the food go after your mouth? What is the last part?” Let your child say the parts in order, using the picture.

Exercise 5A  The parts of the digestive system

1
FWhat is the first part of the digestive system that food enters? Write the word.
2
FWhat is the last part of the digestive system, where waste leaves the body? Write the word.
3
FWhich part is a tube that connects the mouth to the stomach? Write the word.
4
FWhich part comes straight after the stomach? Write the words: small intestine or large intestine.
5
FHow many parts are in the list in section 5.1? Write the number.
6
FWhich part stores waste until it is ready to leave the body? Write the word.
7
FWhich part lies between the small intestine and the rectum? Write the words.
8
FFill in the gap: food passes through one long ___ from the mouth to the anus. Write the word.
9
PSAli says the stomach comes before the mouth in the digestive system. Is Ali right? Write yes or no.
10
PSLook at the picture of the digestive system in section 5.1. Which part is the shape of a long bendy tube, between the mouth and the stomach? Write the word.
11
PSWorking scientifically. Predict which part of the digestive system food reaches after the stomach. Write one prediction.
12
RExplain why the digestive system is described as a tube. Write one sentence.
5.2

What each part of the digestive system does

Year 4
A1: describe the simple functions of the basic parts of the digestive system in humans
Video lesson: What each part of the digestive system doesComing soon
Story. Mo eats a cracker and chews it for a long time. “Why does it start to taste sweet?” he asks. Mr Patel says, “Your mouth starts to break it down, before it even reaches your stomach.”

Each part of the digestive system has a simple job. The table shows what each part does.

PartWhat it does
Mouthteeth chew the food, and saliva starts to break down starchy food
Oesophagusa tube; muscles push the food down to the stomach
Stomachchurns the food and breaks it down with digestive juices
Small intestinefinishes breaking down the food, and absorbs the nutrients into the blood
Large intestineabsorbs water from the food that is left over
Rectumstores the waste until it is ready to leave the body
Anusthe opening where the waste leaves the body

Key ideas

  • The mouth: teeth chew the food, and saliva starts to break it down.
  • The oesophagus: muscles push the food down to the stomach.
  • The stomach: churns the food and breaks it down with digestive juices.
  • The small intestine: absorbs the nutrients into the blood.
  • The large intestine: absorbs water. The rectum stores the waste, and the anus lets it out.
Worked example 5.2.1
Which part absorbs nutrients into the blood? Write the name.

Method. Find the part that absorbs.

  1. Read the table. The small intestine absorbs the nutrients into the blood.
    absorbs nutrients
  2. Name the part. So the small intestine is the part that absorbs nutrients.
    Small intestine
  3. Write the answer.
    Small intestine

Check. Nutrients pass into the blood from the small intestine. ✓

Worked example 5.2.2
Which part churns the food and breaks it down with digestive juices? Write the name.

Method. Find the part that churns.

  1. Read the table. The stomach churns the food and breaks it down with juices.
    churns
  2. Name the part. So the stomach is the part that churns the food.
    Stomach
  3. Write the answer.
    Stomach

Check. The stomach mixes the food with digestive juices. ✓

Worked example 5.2.3
Which part absorbs water from the food that is left over? Write the name.

Method. Find the part that absorbs water.

  1. Read the table. The large intestine absorbs water from the food that is left.
    absorbs water
  2. Name the part. So the large intestine absorbs water.
    Large intestine
  3. Write the answer.
    Large intestine

Check. The large intestine is the last part that absorbs. ✓

Watch out

Watch out: the small intestine absorbs nutrients into the blood, and the large intestine absorbs water. Do not mix up the two parts.

Try it at home or school (with a grown-up). Chew a plain cracker, or a piece of bread, slowly with a grown-up, and notice the taste after a minute. Do not swallow it whole. Spit it into a tissue when finished.

Exam tip

Grown-up tip. Ask: “What is the mouth doing to the food? What does the stomach do with it?” Let your child name one job for each part.

Exercise 5B  What each part of the digestive system does

1
FWhich part uses saliva to start breaking down food? Write the name.
2
FWhich part churns food and breaks it down with digestive juices? Write the name.
3
FWhich part absorbs nutrients into the blood? Write the name.
4
FWhich part absorbs water from the food that is left over? Write the name.
5
FWhat does the oesophagus do? Write the word: pushes or stores.
6
FWhich part stores waste until it is ready to leave the body? Write the name.
7
FWhat does the anus do? Write the word: removes or stores.
8
FFill in the gap: the small intestine absorbs ___ into the blood. Write the word.
9
FWhich part of the digestive system is the longest? Write the name.
10
PSRuby says the stomach absorbs nutrients into the blood. Is Ruby right? Write yes or no.
11
PSMo says food is absorbed in the mouth. Is Mo right? Write yes or no.
12
PSWorking scientifically. Predict what will happen to a cracker in your mouth after you chew it for a minute. Write one prediction with a reason.
13
RExplain why the stomach and the small intestine both help to digest food. Write one sentence.
5.3

Types of teeth

Year 4
A2: identify the different types of teeth in humans and their simple functions
Video lesson: Types of teethComing soon
Story. Priya looks at her dentist’s poster. “Why are some teeth pointed, and some are flat?” she asks. Mr Patel says, “Each type of tooth has a different job, to cut, to tear, or to grind the food.”

Humans have four types of teeth, and each one has a different shape and job. The incisors at the front cut food. The canines are pointed, and tear food. The premolars and molars at the back crush and grind food.

IncisorcutsCaninetearsPremolarcrushesMolargrinds
Four types of tooth: an incisor that cuts, a canine that tears, a premolar that crushes, and a molar that grinds.

An adult has 32 teeth. The table gives the number of each type.

Type of toothNumber in an adultJob
Incisors8cut food; they are sharp and at the front
Canines4tear food; they are pointed
Premolars8crush and chew food; they are at the back
Molars12grind food; they are the big, flat teeth at the back
Total32

Key ideas

  • Incisors cut food, and are at the front.
  • Canines are pointed, and tear food.
  • Premolars and molars are at the back, and crush and grind food.
  • An adult has 32 teeth altogether.
Worked example 5.3.1
How many incisors does an adult have? Write the number.

Method. Read the table.

  1. Find the row. The incisors row shows the number of incisors in an adult.
    incisors
  2. Read the number. An adult has 8 incisors.
    8
  3. Write the answer.
    8

Check. Incisors are the front teeth that cut food. ✓

Worked example 5.3.2
How many teeth are in an adult mouth altogether? Write the number.

Method. Add the four types of tooth.

  1. Add them. 8 incisors, plus 4 canines, plus 8 premolars, plus 12 molars.
    8 + 4 + 8 + 12
  2. Find the total. The total is 32 teeth.
    32
  3. Write the answer.
    32

Check. The table total is 32 too. ✓

Worked example 5.3.3
Which teeth are pointed, and tear food? Write the name.

Method. Find the pointed teeth.

  1. Read the table. Canines are pointed, and they tear food.
    pointed
  2. Name them. So the pointed teeth are the canines.
    Canines
  3. Write the answer.
    Canines

Check. Canines sit beside the incisors. ✓

Watch out

Watch out: a canine is not a molar. A canine is pointed and tears food, while a molar is a large, flat tooth at the back that grinds.

Try it at home or school (with a grown-up). Look in a mirror with a grown-up. Count the teeth at the front of your mouth, and find a pointed tooth. Do not touch your teeth with sharp objects.

Exam tip

Grown-up tip. Ask: “Which teeth do you use to bite an apple? Which teeth do you use to chew bread?” Let your child name the type of tooth they use for each food.

Exercise 5C  Types of teeth

1
FHow many incisors does an adult have? Write the number.
2
FHow many canines does an adult have? Write the number.
3
FHow many premolars does an adult have? Write the number.
4
FHow many molars does an adult have? Write the number.
5
FHow many teeth does an adult have altogether? Write the number.
6
FWhich teeth cut food? Write the name.
7
FWhich teeth grind food at the back of the mouth? Write the name.
8
FFill in the gap: the pointed teeth are called ___. Write the word.
9
FIs enamel the hardest outer layer of a tooth? Write yes or no.
10
PSHow many teeth are at the front of an adult mouth, counting the incisors and the canines together? Write the number.
11
PSA child has 20 teeth with milk teeth. How many fewer teeth does a child have than an adult? Write the number.
12
PSWorking scientifically. Plan a simple survey of your class to find out how many people have a pointed tooth. Write one thing you must keep the same for each person.
13
RExplain why a child has fewer teeth than an adult. Write one sentence.
5.4

Teeth in animals and what they eat

Year 4
A2: identify the different types of teeth and their simple functions, comparing animals that eat different foods
Video lesson: Teeth in animals and what they eatComing soon
Story. At the farm, Leo sees a cow chewing grass, and then at the zoo he sees a lion. “Why do they have such different teeth?” he asks. Ms Chen says, “One eats plants, and one eats meat. Their teeth match their food.”

Animals have teeth that suit the food they eat. A carnivore eats meat. A herbivore eats plants. An omnivore eats both plants and meat.

A carnivore, such as a lion, has sharp canines to tear meat. A herbivore, such as a cow, has flat molars to grind grass and plants. The table compares three animals.

AnimalWhat it eatsTeeth that suit it
Lioncarnivoresharp canines, to tear meat
Cowherbivoreflat molars, to grind grass and plants
Humanomnivoreincisors, canines and molars, for a mixed diet

Key ideas

  • A carnivore eats meat, and has sharp canines to tear it.
  • A herbivore eats plants, and has flat molars to grind them.
  • An omnivore eats both plants and meat.
  • The shape of the teeth matches the food an animal eats.
Worked example 5.4.1
A lion eats meat. Which teeth does it use to tear the meat? Write the name.

Method. Find the lion row.

  1. Read the lion row. The lion has sharp canines, to tear meat.
    sharp canines
  2. Name the teeth. So the lion uses its canines.
    Canines
  3. Write the answer.
    Canines

Check. Canines are pointed and tear food. ✓

Worked example 5.4.2
A cow eats grass. Which teeth grind the grass? Write the name.

Method. Find the cow row.

  1. Read the cow row. The cow has flat molars, to grind grass and plants.
    flat molars
  2. Name the teeth. So the cow uses its molars to grind the grass.
    Molars
  3. Write the answer.
    Molars

Check. Molars are large and flat, which suits grinding plants. ✓

Worked example 5.4.3
Which animal in the table is an omnivore? Write the name.

Method. Find the omnivore in the table.

  1. Read the diet column. The human eats both plants and meat.
    omnivore
  2. Name the animal. So the omnivore in the table is the human.
    Human
  3. Write the answer.
    Human

Check. Humans have incisors, canines and molars for a mixed diet. ✓

Watch out

Watch out: the cow does not have sharp canines for tearing meat. Its flat molars are for grinding plants.

Try it at home or school (with a grown-up). Look at pictures of a dog and a cow in a book with a grown-up. Name what each animal eats, and say which teeth you think it uses most. Discuss your answer.

Exam tip

Grown-up tip. Ask: “What does this animal eat? Which teeth would help with that food?” Let your child match the teeth to the food, and explain the reason.

Exercise 5D  Teeth in animals and what they eat

1
FA lion eats meat. Which teeth tear the meat: canines or molars? Write the word.
2
FA cow eats grass. Which teeth grind the grass: molars or canines? Write the word.
3
FWhich animal in the table is a carnivore? Write the name.
4
FWhich animal in the table is an omnivore? Write the name.
5
FWhich animal in the table is a herbivore? Write the name.
6
FWhich animal has flat molars for grinding plants? Write the name.
7
FWhich animal has sharp canines for tearing meat? Write the name.
8
FA carnivore eats mainly what? Write the word: meat or plants.
9
PSLook at the table in section 5.4. How many of the three animals are omnivores? Write the number.
10
PSRuby says a cow has sharp canines to tear meat. Is Ruby right? Write yes or no.
11
PSWorking scientifically. Predict what teeth a rabbit that eats only grass would have. Write one prediction with a reason.
12
RExplain why a cow does not need sharp canines like a lion. Write one sentence.
5.5

Looking after your teeth and digestive system

Year 4
A1 and A2: the simple functions of the digestive system and teeth, and how to keep them healthy
Video lesson: Looking after your teeth and digestive systemComing soon
Story. Aisha has a sweet after lunch and forgets to brush her teeth. “Will it matter?” she asks. Mr Patel says, “Sugar left on your teeth can cause decay, so brush twice a day to keep them strong.”

Your teeth and digestive system work best when you look after them. Brushing your teeth twice a day with fluoride toothpaste helps to protect them. Sugary food and drinks can cause tooth decay, so have them less often, and choose water to drink.

The table gives five simple habits that help.

HabitWhy it helps
Brush your teethtwice a day, for two minutes, with fluoride toothpaste
Drink waterinstead of sugary, fizzy drinks
Visit the dentistfor regular check-ups
Eat fruit and vegetablesand fibre, which help the digestive system
Keep movingexercise helps the body, including the digestive system

Key ideas

  • Brush your teeth twice a day, for two minutes.
  • Use fluoride toothpaste to help keep your teeth strong.
  • Sugary food and drinks can cause tooth decay.
  • Water is the best drink for your teeth.
Worked example 5.5.1
How long should you brush your teeth for? Write the number of minutes.

Method. Read the habit in the table.

  1. Read the table. Brush for two minutes.
    two minutes
  2. Write the number. So the answer is two minutes.
    2
  3. Write the answer.
    2

Check. Two minutes is long enough to clean every tooth. ✓

Worked example 5.5.2
Which drink is best for your teeth: water or a sugary fizzy drink? Write the word.

Method. Read the table.

  1. Read the habit. The table says to drink water, not sugary, fizzy drinks.
    water
  2. Choose the drink. So water is the best choice for your teeth.
    water
  3. Write the answer.
    water

Check. Sugary drinks can cause tooth decay. ✓

Worked example 5.5.3
Name the ingredient in toothpaste that helps to keep teeth strong. Write the word.

Method. Read the key idea in section 5.5.

  1. Read the key idea. Fluoride toothpaste helps to keep teeth strong.
    fluoride
  2. Check the ingredient. The ingredient that helps the teeth is named in the toothpaste, so it is fluoride.
    named
  3. Write the answer.
    fluoride

Check. Fluoride helps to protect the tooth enamel. ✓

Watch out

Watch out: rinsing with water is not the same as brushing. Brushing removes the food that is left on the teeth, so brush properly.

Try it at home or school (with a grown-up). With a grown-up, brush your teeth for two minutes, using a timer or a song. Brush the front, the back and the top of each tooth. Brush twice a day.

Exam tip

Grown-up tip. Ask: “How long did you brush? Did you brush the back teeth?” Help your child to brush for two minutes, and to visit the dentist for regular check-ups.

Exercise 5E  Looking after your teeth and digestive system

1
FHow many times a day should you brush your teeth? Write the number.
2
FHow many minutes should you brush your teeth for? Write the number.
3
FWhich food is more likely to cause tooth decay: sugary food or plain bread? Write the words: sugary food.
4
FWhich drink is best for your teeth: water or a sugary fizzy drink? Write the word.
5
FWhat is the name of the ingredient in toothpaste that helps to keep teeth strong? Write the word.
6
FWhich two times of day should you brush your teeth? Write the words: morning and ___. Write the word.
7
FFill in the gap: a visit to the dentist for a ___ helps to find problems early. Write the word.
8
FName one habit from the table that helps the digestive system. Write one habit.
9
PSA friend says teeth can be cleaned well just by rinsing with water. Is the friend right? Write yes or no.
10
PSWorking scientifically. Write one question you could ask a class to find out how many people brush their teeth twice a day.
11
RExplain why sugary food is a problem for teeth, in one sentence. Write one sentence.

Chapter summary

SkillMethod
Digestive systemFood passes from the mouth, through the oesophagus, stomach, small and large intestines and rectum, to the anus.
What the parts doMouth chews and starts digestion. Stomach churns. Small intestine absorbs nutrients. Large intestine absorbs water.
TeethIncisors cut, canines tear, premolars crush, molars grind. An adult has 32 teeth.
Teeth and dietA carnivore has sharp canines. A herbivore has flat molars. An omnivore eats both.
Looking after teethBrush twice a day with fluoride toothpaste. Drink water, and have sugary food less often.

Can you…?

  • I can name the parts of the digestive system in order, from the mouth to the anus
  • I can say what the mouth, stomach, small intestine, large intestine and rectum do
  • I can name the four types of teeth, and say what each one does
  • I can count the teeth in an adult and compare them with a child
  • I can match an animal’s teeth to the food it eats
  • I can say simple ways to keep my teeth and digestive system healthy

Key terms

digestive system
the long tube and its parts that break down food
oesophagus
the tube that pushes food from the mouth to the stomach; also called the gullet
saliva
a liquid in the mouth that starts to break down starchy food
nutrients
the useful parts of food that the body needs, absorbed into the blood
absorb
to take something in, such as nutrients into the blood
incisor
a sharp front tooth, used to cut food
canine
a pointed tooth, used to tear food
molar
a large, flat tooth at the back, used to grind food
carnivore
an animal that eats mainly meat
herbivore
an animal that eats only plants
omnivore
an animal that eats both plants and meat
tooth decay
damage to a tooth, caused by sugar left on the teeth

Exercise 5Z  Check-up

1
Name the part of the digestive system where food enters the body. Write the word.
2
Which part of the digestive system absorbs nutrients into the blood? Write the name.
3
Which part of the digestive system churns the food and breaks it down? Write the name.
4
Which part of the digestive system stores waste until it leaves the body? Write the name.
5
How many incisors does an adult have? Write the number.
6
An adult has 32 teeth. How many molars are there, and what do molars do? Write the number and the job.
7
Which teeth are pointed, and tear food? Write the name.
8
A lion has sharp canines. What does it eat? Write the word: meat or plants.
9
Name one habit that helps to keep your teeth healthy. Write one habit.
10
Explain why a cow has flat molars rather than sharp canines. Write one sentence.

Total 18 marks. Allow about 18 minutes.

Exercise 5X  Practice test questions

1
FWhich part of the digestive system is the first part that food enters? Write the name.[1 mark]
2
FWhich part connects the mouth to the stomach? Write the name.[1 mark]
3
FWhich teeth cut food at the front of the mouth? Write the name.[1 mark]
4
FAn adult has 8 incisors, 4 canines, 8 premolars and 12 molars. How many teeth does an adult have altogether? Write the number.[2 marks]
5
FWhich part of the digestive system absorbs water from the food that is left over? Write the name.[2 marks]
6
FWrite the name of the teeth that grind food at the back of the mouth.[1 mark]
7
FA lion eats meat, and a cow eats grass. Write the name of the teeth that tear meat, and the name of the teeth that grind grass.[3 marks]
8
FName the part of the digestive system that stores waste before it leaves the body, and say where the waste leaves. Write the two names.[2 marks]
9
RRuby says that brushing her teeth at night is important because sugar can cause decay. Explain why, in one sentence.[2 marks]
10
RExplain how the stomach and the small intestine work together to digest food. Write one sentence.[3 marks]
← Chapter 4: Habitats, change and food chainsChapter 6: Solids, liquids and gases →

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