Parts and functions of the digestive system
This Topic is About...
- I will learn about the parts of the human digestive system and their functions.
- I will make a model digestive system.
- I will investigate digestion in the mouth.
- I will identify dangers in an investigation and know how to work safely.
- I will make a conclusion from results.
- I will learn that the digestive systems of other animals are similar to ours.
You’re going to be a science explorer!
Key Words
- anus
- digestion
- digestive system
- large intestine
- oesophagus
- saliva
- small intestine
- stomach
Tap to Learn the Meanings!
- anus: The opening at the end of the digestive system through which waste leaves the body.
- digestion: The process of breaking down food into nutrients the body can use.
- digestive system: The organs that help break down food and absorb nutrients.
- large intestine: The part of the digestive system where water is absorbed and waste is formed.
- oesophagus: The tube that carries food from the mouth to the stomach.
- saliva: A watery liquid in the mouth that helps break down food and aids in swallowing.
- small intestine: The part of the digestive system where most digestion and nutrient absorption happens.
- stomach: The organ that breaks down food using stomach acids and enzymes.
Great job learning new science words!
The Human Digestive System
FYour body needs food to help it grow. Food also gives you energy. But your body cannot use the food you eat just as it is. Food has to be changed so that it can be used by the body. The digestive system changes food by breaking it down into tiny particles. This process is called digestion. The stomach and small intestine digest the food. They are the main organs of the digestive system. The mouth also digests some foods. Digested food particles pass from the small intestine into the blood and are carried to all parts of the body.
Digestion starts in the mouth. Your teeth chew and chop up the food into smaller pieces that we can swallow. Saliva makes the food moist which also makes swallowing easy. Digestive juices in saliva start to digest the food.
The small intestine breaks down the food even more until the food particles are small enough to move into the blood.
The solid undigested food bits are pushed out of the body as waste through the open end of the large intestine, called the anus.
How Food is Digested
TThe food moves down a tube called the oesophagus and into the stomach. The food is mixed with digestive juices and churned into a liquid. Inside the stomach, food mixes with digestive juices to form a paste called chyme.
Any undigested food moves into the small intestine where it is absorbed into the blood.
Now we are ready for the next stage of digestion where any undigested food that has passed into the large intestine is pushed out of the body.
🔍 Think like a Scientist 1 — Make a Model Digestive System
🧰 You will need: materials such as plastic bottles, plastic tubing, plastic bags, balloons, string, paper cups, cardboard tubes, bicycle inner tube, old pantyhose (tights), scissors, elastic bands, electrical tape
🧪 Task: Design and make a model of the digestive system.
- Your model should be made of everyday or waste materials.
- Show the parts of the digestive system in the correct order.
💭 Think about:
- The structure and function of each part of the digestive system — for example, the oesophagus is a long, narrow tube.
- This will help you choose the best materials for the different parts.
🪄 Instructions:
- Place your completed model on a piece of cardboard or hardboard.
- Use glue or sticky putty to hold it in place.
- Use your model to explain to a partner how the digestive system works.
💡 Reflection Time — Tap to Think!
- What materials worked best for each organ? 🧩
- How did you show the movement of food through your model? 🍞➡️
- Can you explain what happens in each part of your model? 🧠
Amazing work! You’ve just modelled how your body digests food. 🌟👏
FUN QUESTIONS
1. Why do we need food?
Show me!
2. Why must food be digested?
Show me!
3. How does the mouth help digestion?
Show me!
4. What is the name of the tube that joins the mouth to the stomach?
Show me!
5. What is the stomach's function in digestion?
Show me!
6. Which part of the digestive system removes undigested wastes?
Show me!
7. How does the digested food reach all parts of the body?
Show me!
🔍 Think like a Scientist 2 — Investigate Digestion in the Mouth
🧰 You will need: bread, iodine solution, two saucers, a dropper, and a spoon
⚠️ Safety First:
- Do not drop iodine on your clothes — it stains! 🧼
- Do not taste or swallow any iodine — it is harmful. 🚫
🧪 Method:
- Put a small piece of bread on a saucer. Add a drop of iodine solution.
- a) What do you observe?
- b) What does this show about the bread?
- Place a small piece of bread in your mouth and chew it. Keep it in your mouth without swallowing for about three minutes.
- Does the taste of the bread change? How does it change?
- Take the chewed bread out with a spoon and place it on another clean saucer. Add a drop of iodine solution.
- a) What do you observe?
- b) What does your observation tell you about the bread?
- c) How do you think the bread has changed while in your mouth?
- Check the investigation for any possible risks:
- a) Is anything in this activity dangerous?
- b) Suggest a way you can work safely. 🧤
- Make a conclusion for your investigation.
- a) What is your conclusion?
- b) Why did you make that conclusion?
🌟 Tap to Reveal Observations and Conclusions
- Observation: The bread turned blue-black with iodine, showing that it contained starch. 🍞🧪
- After Chewing: The chewed bread showed a lighter or no colour change because some starch changed into sugar. 😋
- Conclusion: Saliva breaks down starch into sugar in the mouth. This shows digestion starts in the mouth! 🦷💧
- Safety Reminder: Never taste or touch iodine. Use clean tools and wash your hands after. 🧤
Fantastic work, young scientist! You’ve discovered the start of digestion! 🌟👏
🐾 Digestive Systems of Other Animals
Many vertebrates have digestive systems that are quite similar to ours. Just like humans, they have organs such as the mouth, oesophagus, stomach, intestines, and anus that work together to break down food and absorb nutrients.
Although the general layout is similar, the length and shape of the digestive systems vary depending on the animal’s diet. For example, herbivores like rabbits have longer intestines to digest plant material, while carnivores like cats have shorter systems designed for digesting meat.
🤔 FUN QUESTIONS — Animal Digestion
1. Which parts of the animal digestive systems in the pictures are the same as the human digestive system? 🧍♂️🐇🐈
🌟 Show me!
2. Compare the following parts of the cat and rabbit digestive systems:
- a) Oesophagus
- b) Stomach
- c) Small intestine
- d) Large intestine
🧠 Tap to see!
3. In which animal do you think digestion takes longer? Say why. ⏳
💡 Reveal answer!
4. Why do you think the digestive systems of the cat and rabbit are different in some ways? 🤓