Learning objectives
Knowledge
- To describe the function of the human digestive system.
Working scientifically
- To evaluate a model.
Success criteria
Knowledge
- I can list the main organs of the human digestive system.
- I can describe the function of the main organs of the digestive system.
Working scientifically
- I can explain how a model has been used to show a part of the digestive system.
- I can identify a weakness in the model used to represent the digestive system.
National curriculum
Science
Humans, including animals
Pupils should be taught to:
- Describe the simple functions of the basic parts of the digestive system in humans.
Working scientifically
Pupils should be taught to use the following practical scientific methods, processes and skills:
- Using results to draw simple conclusions, make predictions for new values, suggest improvements and raise further questions.
Cross-curricular links
English
Spoken language
Pupils should be taught to:
- Listen and respond appropriately to adults and their peers.
- Ask relevant questions to extend their understanding and knowledge.
- Use relevant strategies to build their vocabulary.
- Articulate and justify answers, arguments and opinions.
See National curriculum - English - Key stages 1 and 2.
British values
- The rule of law.
- Tolerance of those with different faiths and beliefs.
See Promoting fundamental British values as part of SMSC in schools (non-statutory advice) – contains public sector information licensed under the Open Government Licence v2.0.
Before the lesson
Check all images, videos, links and presentation slides are suitable for your class.
- Presentation: Observing the digestive system in the past.
- Presentation: Labelling and modelling the digestive system.
- Bread (one bite-sized piece each).
- Equipment for modelling the digestive system (optional – one set for the teacher, see Main event):
- cereal;
- 1 potato masher;
- 2 large bowls (one labelled blood);
- 1 small jug of water (labelled saliva);
- 1 small jug of fruit juice (labelled acid);
- 1 funnel and tubing if available;
- 1 resealable freezer bag;
- 1 pair of tights;
- 1 sponge;
- 1 tray;
- scissors.
The Knowledge organiser provides a visual summary of the key facts and vocabulary for the unit. The children can use it as directed to check keyword meanings or spellings and to help them remember important information when completing an activity. However, be aware that sharing the outcomes of the planned enquiries at this stage of the unit may spoil the discovery element of the practical work. Find further ideas for using the Knowledge organiser to support adaptive teaching here.
This unit is a biology topic. Biology is the study of living things and their processes.
Informing the pupils about the specific branch of science that this unit belongs to is at the teacher’s discretion.
Subject knowledge
- Digestion includes both mechanical (physical breaking up) and chemical (use of acid and enzymes) digestion to break the food into smaller pieces; this prevents blockages and ensures molecules are small enough to be absorbed through the digestive system into the blood.
- Digestion begins in the mouth, where the teeth physically break up food and saliva softens and begins to digest the food chemically.
- When swallowing food, the epiglottis (a flap at the back of the throat) directs food down the oesophagus and away from the trachea (windpipe).
- The oesophagus is muscular and actively squeezes food along to the stomach. It means people can swallow even upside down (although this is not advised as it is a choking hazard).
- Strong stomach acid breaks down food further in the stomach. If the acid moves up into the oesophagus, it can damage any structures it contacts. People experience this as heartburn or acid reflux.
- The average adult small intestine is approximately six and a half metres long.
- The large intestine is wider in diameter than the small intestine, approximately one and a half metres long and responsible for absorbing water back into the bloodstream.
Note: the digestive system of animals can differ.
Misconceptions
The children may think that:
- ‘Digestion starts in the stomach’ – digestion starts in the mouth.
- ‘Digestion continues into the large intestine’ – no digestion occurs in the large intestine, just water absorption.
- ‘The digestive system has two outlets; one for faeces and one for urine’ – there is only one outlet from the digestion system which removes faeces. The kidneys (part of the urinary system) filter water from the blood and produce urine.
- ‘The stomach is located by the navel’ – the stomach is located just below the ribs.
- ‘A food group is the same as a nutrient group’ – a nutrient group refers to the molecules essential for life (carbohydrates, proteins, fats/lipids, vitamins, minerals, fibre and water) rather than foods with similar nutritional values.
- ‘The appendix is part of the digestive system’ – although it is attached to the large intestine, it does not play a role in digestion.
Lesson organisation
Use the Resource Stretch and Challenge: Digestion and food as an extension and revision opportunity. Throughout the unit, the children can select activities and complete them independently in their books.
The information within this section provides basic generic guidance only and is not tailored to the circumstances of your school or class. You must ensure you refer to and follow your own school’s health & safety policy and complete any necessary risk assessments. If you know a child has specific issues, consider discussing the lesson with them in advance and adapting it as needed. They might benefit from adult support. If problems emerge during the lesson, consult your Senior Leadership Team. It is the teacher’s responsibility to check all resources and lesson content to ensure it is suitable for their class setting.
Health and safety
- Do not give bread containing gluten to children with a gluten allergy/intolerance.
- Depending on the bread selection, there is a potential risk for seed/nut allergic reactions.
Sensitivities
Some pupils may ask questions or know about a stoma (an opening that connects part of the intestine to the outside surface of the abdomen).
- In this case, faeces does not leave via the anus but is collected in a bag outside the body.
- A stoma can be a temporary or permanent solution to various digestive complications.
Lesson plan
1: Recap and recall
Before starting this unit, check the children can recall the following key facts from units Science, Year 2, Animals: Life cycles and health and Science, Year 3, Animals: Movement and nutrition:
- Humans need air/oxygen, food/nutrients and water to survive.
- The life processes include movement, reproduction, sensitivity, growth, excretion and nutrition.
- The seven nutrient groups are carbohydrates, protein, fats and oil, fibre, vitamins, minerals and water.
- Muscles cause movement in our bodies.
Use the Activity: Recap and recall digestion mind map (one each) if needed to elicit the children’s prior knowledge.
2: Attention grabber
Give each pupil a small piece of bread and ask them to hold it in their mouth without chewing or swallowing for about 30 seconds.
Ask them:
- What nutrient group does the bread contain the most? (Carbohydrates.)
- How has the bread changed? (Answers may include that it became wet, soft, slippery or sweet.)
- Why has the bread changed? (Saliva in our mouths has started breaking down the bread’s carbohydrates into sugars. This is an example of digestion.)
3: Main event
Use the equipment for modelling the digestive system in the Have ready and follow the Teacher video: Modelling the digestive system to demonstrate it to the children. Alternatively, play the Pupil video: Modelling the digestive system.
Pupil video: Modelling the digestive system
Pause the video or teacher demonstration and ask the children to identify which organ each item represents and how each organ aids the digestive process (see Teacher video: Modelling the digestive system).
Encourage the children to consider why the materials used in the model have been selected and evaluate how effective they are in modelling the process:
- What parts of the model worked well? (Answers may include the teeth chewing or the squeezing of food through the digestive system.)
- What parts of the model do not represent the real body well? (Answers may include the absence of actual chemicals; the model being broken up rather than continuous; liquid coming out of the small intestine when it should not; food not passing through a tube for the large intestine; the time frame not being realistic. Encourage the children to suggest alternative models or equipment.)
Observing the digestive system in the past
Display slides 1 and 2 of the Presentation: Observing the digestive system in the past and read through the story explaining how stomach acid was first observed.
Presentation: Observing the digestive system in the past
Display slide 3 and allow time for paired discussion. Take feedback and discuss as a class:
- Why did doctors in the past usually use dead bodies to learn from? (They did not have the equipment to see inside a living body safely.)
- How do scientists and doctors observe inside the body now? (Probes and swallowable cameras; surgery is still used but with anaesthesia and antibiotics.)
- Do you think the doctor should have tried harder to close the wound, even if it meant he could not observe inside the stomach? (This is an ethical issue with many points of view to consider.)
The human digestive system diagram
As a class, watch the Pupil video: The human digestive system to recap the order of the organs in the digestive system and their functions.
Pupil video: The human digestive system
Hand out the Activity: Digestive system diagram (one each) and ask the children to name, describe the function and identify the equipment used to represent each organ.
4: Wrapping up
Display the Presentation: Labelling and modelling the digestive system and select volunteers to drag the labels into the correct places. Click to reveal the answers.
Presentation: Labelling and modelling the digestive system
Questions
- What are the main organs in the digestive system? (Mouth, teeth, tongue, oesophagus, stomach, small and large intestine.)
- What parts of the digestion model did not work well?
- How could you improve the model?
Extended-mode explainer videos
How to extend your display to view the lesson page and preseantion mode simultaneously. Choose your operating system below to watch the video
If you need further support with extending your display,
please contact [email protected].
Extended-mode explainer video: For Mac
Extended-mode explainer video: For Windows
Adaptive teaching
Pupils needing extra support
Should use the Activity: Digestive system diagram: support version; could have the Pupil video: The human digestive system playing in the background; could use the Knowledge organiser while they work to refer to the parts of the digestive system and their functions.
Pupils working at greater depth
Should add notes surrounding the diagram about the model’s strengths and weaknesses; should suggest improvements to overcome the weaknesses described; could choose an extension activity relating to the digestive system from the Resource: Stretch and challenge: Digestion and food.
Assessing progress and understanding
Pupils with secure understanding indicated by: labelling key organs found in the digestive system and describing each function; explaining how the model represented each key function of the digestive system; identifying a strength or weakness of the model.
Pupils working at greater depth indicated by: evaluating the effectiveness of the model digestive system by considering strengths and weaknesses and suggesting improvements.
Knowledge outcomes
- I can list the main organs of the human digestive system, including the mouth, tongue, oesophagus, stomach, small intestine and large intestine.
- I can describe the function of the oesophagus as carrying food to the stomach.
- I can describe the function of the stomach is to break up food.
- I can describe the functions of the small intestines as breaking up food and absorbing nutrients into the blood.
- I can describe the function of the large intestine as absorbing water from food into the blood.
Vocabulary definitions
-
absorb
To take in or soak up.
-
diagram
A simple 2D drawing with labels.
-
digest
To break up food into smaller pieces.
-
digestive system
The group of organs that break down food and absorb nutrients.
-
ethics
Ideas about what is right or wrong.
-
evaluate
To judge and form an opinion on something using positives and negatives.
-
faeces
Solid waste from the digestive system.
-
large intestine
The organ where water is absorbed into the blood.
-
model
Something that is used to represent something else.
-
nutrient
A substance that is essential for survival or growth.
-
oesophagus
A tube that carries food from the mouth to the stomach.
-
saliva
The liquid produced in the mouth to help chewing, swallowing and digestion.
-
small intestine
An organ where food is broken down and nutrients are absorbed into the blood.
-
stomach
A sac-like structure where food is broken down by acid.
-
tooth
Enamel-covered structure in the jaw for biting and chewing.
-
tongue
The muscle in the mouth used for speaking, tasting and swallowing.