Year 9 Biology: Human Digestive System Organisation and Digestive System

Introduction to the Digestive System

The human digestive system is like a long, twisting tube that helps us break down food into smaller pieces so our bodies can use it. This system is made up of several organs that work together to digest the food we eat.

Key Parts of the Digestive System

1. Mouth

• Function: The digestive process begins here. We chew food with our teeth, breaking it into smaller pieces. Saliva mixes with the food to start breaking it down.
• Tip: Remember, chewing is important! It helps our stomach digest food more easily.

2. Oesophagus

• Function: This is a tube that connects the mouth to the stomach. It moves food down through a series of muscle contractions called peristalsis.
• Visual: Think of it like a slide that helps food go down smoothly!

3. Stomach

• Function: The stomach is a muscular bag that mixes food with digestive juices. It helps break down proteins and kills harmful bacteria.
• Key Point: The stomach can hold food for several hours while it digests.

4. Small Intestine

• Function: This is where most digestion occurs. The small intestine absorbs nutrients from the food into the bloodstream.
• Tip: It is very long (about 6-7 metres!) and has tiny villi that help absorb more nutrients.

5. Large Intestine

• Function: This part absorbs water and forms waste (faeces) to be excreted. It is shorter but wider than the small intestine.
• Key Point: Keeping hydrated is important for the large intestine to work properly!

6. Rectum and Anus

• Function: The rectum stores waste until we are ready to go to the toilet. The anus is the opening through which waste leaves the body.
• Tip: Regular bathroom trips help keep our digestive system healthy!

How the Digestive System Works

1. Ingestion: We take in food through our mouth.
2. Digestion: Food gets broken down into smaller parts.
3. Absorption: Nutrients are absorbed into the bloodstream in the small intestine.
4. Excretion: Waste is formed and eventually expelled from the body.

Fun Facts

• Did you know that the total length of the digestive system is about 9 metres?
• Your stomach has a special lining that protects it from its own acids!

Questions for Review

Easy Level Questions

1. What is the first part of the digestive system?
2. What do we use our teeth for in digestion?
3. What does the oesophagus do?
4. What happens in the stomach?
5. Where does most digestion take place?
6. What does the large intestine absorb?
7. What is the purpose of the rectum?
8. What is the final step of the digestive process?
9. How long is the small intestine?
10. What protects the stomach from its own acids?
11. What do we call the waste that leaves our body?
12. Why is chewing important in digestion?
13. Which organ connects the mouth and stomach?
14. What are villi?
15. What do digestive juices do?
16. How does food move through the oesophagus?
17. Why is water important for the digestive system?
18. What happens to food in the small intestine?
19. How does the body get nutrients from food?
20. What is the role of saliva in digestion?

Medium Level Questions

1. Describe the process of peristalsis.
2. How do the organs of the digestive system work together?
3. What is the function of saliva?
4. How does the stomach break down food?
5. Why is the small intestine so long?
6. What happens if the large intestine doesn’t absorb enough water?
7. Explain the journey of food from the mouth to the anus.
8. What role do enzymes play in digestion?
9. How are nutrients absorbed in the small intestine?
10. What happens to undigested food in the large intestine?
11. What are some examples of nutrients we get from food?
12. How does the body use the nutrients it absorbs?
13. Why is the lining of the stomach important?
14. How does a balanced diet affect digestion?
15. What is the importance of dietary fibre for the digestive system?
16. What might happen if we do not chew food properly?
17. How do different foods affect digestion?
18. Why do some people have trouble digesting certain foods?
19. What is the role of the pancreas in digestion?
20. How does the liver assist in the digestive process?

Hard Level Questions

1. Explain how the pH of the stomach aids digestion.
2. Discuss the role of gut bacteria in the digestive system.
3. What are the consequences of a poor diet on the digestive system?
4. How do hormones affect digestion?
5. Describe the impact of stress on the digestive system.
6. What is the role of bile in digestion?
7. Explain the difference between mechanical and chemical digestion.
8. How does the structure of the small intestine facilitate absorption?
9. What are the signs of digestive disorders?
10. How can lifestyle choices affect digestion?
11. What are some common digestive problems?
12. Explain the concept of digestion in relation to energy metabolism.
13. How does aging affect the digestive system?
14. What is the role of the gallbladder in digestion?
15. How does the body regulate the digestive process?
16. Discuss the importance of hydration for digestive health.
17. What happens to food that is not digested?
18. Explain the relationship between the digestive system and the immune system.
19. What methods can improve digestive health?
20. How does the digestive system interact with other systems in the body?

Answers

Easy Level Answers

1. Mouth
2. To chew food.
3. It moves food to the stomach.
4. It mixes food with digestive juices.
5. In the small intestine.
6. Water.
7. It stores waste.
8. Excretion.
9. About 6-7 metres.
10. The stomach lining.
11. Faeces.
12. It helps break down food.
13. Oesophagus.
14. Tiny hair-like structures that absorb nutrients.
15. They help break down food.
16. Through muscle contractions.
17. To help absorb nutrients.
18. Food is broken down into smaller parts.
19. Through the bloodstream.
20. Saliva helps start digestion.

Medium Level Answers

1. It is a series of muscle contractions that move food.
2. They work in a sequence to digest food.
3. It helps break down food and lubricates it.
4. It uses acids and enzymes.
5. To increase the area for absorption.
6. You could become dehydrated.
7. Food goes from the mouth to the oesophagus to the stomach to the small intestine and finally to the anus.
8. They help break down food into smaller molecules.
9. Nutrients are absorbed through the walls of the small intestine.
10. It becomes faeces.
11. Carbohydrates, proteins, fats, vitamins, and minerals.
12. For growth, energy, and repair.
13. It prevents damage from acids.
14. It helps with digestion and nutrient absorption.
15. It helps the large intestine form waste.
16. Food may not digest properly.
17. Different foods require different enzymes.
18. Some foods are harder to digest than others.
19. It produces enzymes that break down food.
20. The liver produces bile that helps digest fats.

Hard Level Answers

1. It helps break down food and kills bacteria.
2. They help digest food and produce vitamins.
3. It can lead to digestive disorders.
4. They help regulate the digestive process.
5. It can cause issues like indigestion.
6. Bile helps emulsify fats for digestion.
7. Mechanical digestion breaks food into smaller pieces; chemical digestion breaks it down chemically.
8. It has a large surface area with villi for absorption.
9. Symptoms include pain, bloating, and irregular bowel movements.
10. Poor diet can lead to constipation and other issues.
11. Common problems include bloating, constipation, and heartburn.
12. Digestion provides energy for the body.
13. It may slow down digestion.
14. It stores bile for fat digestion.
15. The body uses hormones to signal hunger and fullness.
16. Water helps dissolve nutrients and keep things moving.
17. It is removed from the body as waste.
18. A healthy gut supports the immune system.
19. Eating a balanced diet and staying active can help.
20. The digestive system works with the circulatory and nervous systems.