The shape of the lesson
By the end of the lesson, learners can
- The organs, in order: Click each organ in the 3D model, or press Follow a mouthful and watch the food travel from mouth to anus.
- Five processes of nutrition: In the sim the PROCESS readout names what each organ does.
- Alimentary canal: mouth, oesophagus, stomach, duodenum, ileum, colon, rectum, anus.
- Associated organs: salivary glands, pancreas, liver, gall bladder; food does not pass through them.
- Absorption is into the blood; assimilation is uptake and use by cells.
- Egestion removes undigested food; it is not excretion.
One picture every idea returns to
Food passes along the alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum then ileum) and large intestine (colon, rectum, anus). The salivary glands, pancreas, liver and gall bladder are associated organs that the food never passes through. Five processes happen on the way: ingestion, digestion, absorption, assimilation and egestion.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, One long tube, from mouth to anus.. The alimentary canal is one long, muscular tube with organs along its length that take food in, break it down, absorb what is useful and get rid of the rest. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: The organs, in order | Click each organ in the 3D model, or press Follow a mouthful and watch the food travel from mouth to anus. Project tab 2 of the lab (The digestive system in 3D) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Five processes of nutrition | In the sim the PROCESS readout names what each organ does. | Frayer Model |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 21 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Five processes of nutrition, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Frayer Model
Pairs fill a four-box grid for the key term: definition, characteristics, examples and non-examples. The non-examples box is where the misconceptions surface, so give it the most time.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| The liver, pancreas, gall bladder and salivary glands are not part of the alimentary canal: food never passes through them. | They secrete juices into it. |
| Egestion is not excretion. | Faeces are mostly undigested food that never entered the body's cells; excretion removes waste products of metabolism, such as urea and carbon dioxide. |
The digestive system: worksheet
6 questions, 21 marks. Written in the style of the papers; no past paper question is reproduced.
List, in order, the parts of the alimentary canal that food passes through from the mouth to the anus.
Define each term: (a) ingestion, (b) digestion, (c) absorption, (d) assimilation, (e) egestion.
Name the organ that makes bile, the organ that stores it, and the part of the alimentary canal that bile enters.
Four organs are labelled P, Q, R and S on a diagram. P secretes amylase, protease and lipase into the duodenum. Q absorbs most of the digested food. R stores faeces. S carries food to the stomach by peristalsis. Name P, Q, R and S.
A student writes: "Faeces are excreted through the anus." Explain why this is incorrect.
A meal took the following times to pass through each region: mouth 1 minute, oesophagus 10 seconds, stomach 3 hours, small intestine 5 hours, large intestine 24 hours. (a) Calculate the total time spent in the stomach and small intestine together, in minutes. (b) Suggest why food stays a long time in the small intestine.
Answer key and marking notes
- Mouth, oesophagus, stomach.
- Duodenum, ileum (small intestine).
- Colon, rectum (large intestine).
- Anus. (Full marks for the complete correct order; lose one mark for each error.)
- (a) Ingestion: the taking of substances, such as food and drink, into the body.
- (b) Digestion: the breakdown of food.
- (c) Absorption: the movement of nutrients from the intestines into the blood.
- (d) Assimilation: the uptake and use of nutrients by cells.
- (e) Egestion: the removal of undigested food from the body as faeces.
- Made by the liver.
- Stored in the gall bladder.
- Enters the duodenum (first part of the small intestine).
- P: pancreas.
- Q: ileum (small intestine).
- R: rectum.
- S: oesophagus.
- Faeces are mostly undigested food that has never been absorbed into body cells, so their removal is egestion.
- Excretion is the removal of waste products of metabolism (such as urea or carbon dioxide) made inside cells.
- (a) 3 h + 5 h = 8 h = 8 × 60 = 480 minutes.
- (b) Chemical digestion is completed there, and there must be enough time for the digested nutrients and most of the water to be absorbed into the blood.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which organ is part of the alimentary canal?
- ADuodenum
- BPancreas
- CLiver
- DGall bladder
What is meant by egestion?
- AThe removal of undigested food from the body as faeces
- BThe removal of waste products of metabolism, such as urea
- CThe taking of food and drink into the body
- DThe uptake and use of nutrients by the body's cells
Which organ releases bile into the duodenum?
- AGall bladder
- BPancreas
- CStomach
- DSalivary glands
The diagram shows part of the digestive system. Which letter labels the organ that secretes amylase, protease and lipase into the duodenum?
- AC
- BA
- CB
- DD
In which order does food pass through these parts of the alimentary canal?
- Aoesophagus, stomach, duodenum, ileum, colon
- Boesophagus, duodenum, stomach, ileum, colon
- Cstomach, oesophagus, ileum, duodenum, colon
- Doesophagus, stomach, ileum, colon, duodenum
Amino acids absorbed from the ileum are used by muscle cells to make new proteins. Which process is this?
- AAssimilation
- BAbsorption
- CDigestion
- DIngestion
A person has a blockage in the tube that carries bile from the gall bladder. Which process in the alimentary canal is most directly affected?
- ADigestion of fats in the small intestine
- BDigestion of starch in the mouth
- CAbsorption of water in the colon
- DChurning of food in the stomach
A doctor removes most of a patient's colon. Which effect is most likely?
- AFaeces are more watery, as less of the remaining water is absorbed
- BProtein is no longer digested, as the colon makes protease
- CGlucose is no longer absorbed, as the colon absorbs most nutrients
- DFood cannot be swallowed, as peristalsis starts in the colon
Quiz key
The duodenum is the first part of the small intestine, so food passes through it. The pancreas, liver and gall bladder are associated organs: they secrete or store juices that flow into the alimentary canal, but food never passes through them.
Egestion is the removal of undigested food from the body as faeces, through the anus. Removing waste products of metabolism such as urea is excretion. Taking in food and drink is ingestion. Uptake and use of nutrients by cells is assimilation.
Bile is made in the liver, stored in the gall bladder and released from the gall bladder into the duodenum. The pancreas releases pancreatic juice containing enzymes. The stomach releases gastric juice. Salivary glands release saliva into the mouth.
C is the pancreas, which secretes pancreatic juice containing amylase, protease and lipase into the duodenum. A is the stomach, which secretes gastric juice with protease and acid but no lipase. B is the liver, which makes bile, not enzymes. D is the colon, which absorbs some remaining water and secretes no digestive enzymes.
Food goes from the oesophagus to the stomach, then into the small intestine (duodenum first, then ileum), and then into the large intestine (colon). Putting the duodenum before the stomach, or the stomach before the oesophagus, reverses real steps. The duodenum cannot come after the colon, because it is the start of the small intestine.
Assimilation is the uptake and use of nutrients by cells, such as building proteins from absorbed amino acids. Absorption is the earlier movement of the amino acids from the intestine into the blood. Digestion is the breakdown of food, which here has already happened. Ingestion is taking food into the mouth.
Bile enters the duodenum and helps the digestion of fats (by emulsifying them and neutralising acid), so fat digestion in the small intestine is affected most. Starch digestion in the mouth uses salivary amylase, which is unaffected. Water absorption in the colon does not depend on bile. Churning in the stomach happens before bile is added.
The colon absorbs some of the water that remains after the small intestine, so without it faeces are more watery. Protein is digested in the stomach and small intestine; the colon makes no protease. Glucose and other nutrients are absorbed in the small intestine. Swallowing and peristalsis in the oesophagus do not depend on the colon.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.