Understanding the Respiratory System: Functions and Mechanisms

1. KS4 Physical Education The Respiratory System These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates that the slide contains activities created in Flash. These activities are not editable. For more detailed instructions, see the Getting Started presentation.

2. Learning objectives What we will learn in this presentation: • The structures of the respiratory system and their functions • The mechanisms of breathing • How gases are exchanged during breathing • The composition of inhaled and exhaled air.

3. The role of the respiratory system The respiratory system helps the body obtain oxygen for respirationand remove the waste product carbon dioxide. As we breathe, oxygen moves through the surface of the lungs into the body. It is then absorbed by the blood cells and transported around the body via the blood vessels. The respiratory system is adapted for efficient exchange of gases between the lungs and the blood.

4. The respiratory system

5. Mechanisms of breathing – inspiration When you breathe in: Intercostal muscles pull ribs up and out • theintercostal muscles between the ribs contract, pulling the chest walls up and out. • the diaphragm muscle below the lungs contracts and flattens, increasing the size of the chest. • the lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth. Diaphragm contracts and moves down

6. Mechanisms of breathing – inspiration

7. Mechanisms of breathing – expiration When you breathe out: • theintercostal muscles between the ribs relax so that the chest walls move in and down. • the diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest. • the lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth. Ribs move in and down Diaphragm relaxes and bulges up

8. Mechanisms of breathing – expiration

9. Gas exchange at the alveoli The alveoli are bunches of tiny air sacks inside the lungs. Each individual sack is called an alveolus. When you breathe in, they fill with air. The alveoli are covered in tiny capillaries (blood vessels). Gases can pass through the thin walls of each alveolus and capillary, and into the bloodstream. Gases can also pass from the bloodstreaminto the alveolus.

10. Gas exchange at the alveoli

11. Composition of inhaled and exhaled air 17% 3% 79% Large amount 21% Very small amount 79% Small amount What are the main differences between inhaled and exhaled air? Why does mouth-to-mouth resuscitation work?

12. The nasal passages and lungs Air is drawn into the body via the nose or mouth. There are advantages to breathing through your nose: • the air is warmed so that it is closer to body temperature • tiny hairs and mucus in the nose filter the air, preventing larger dust and pollen particles reaching the alveoli • mucus moistens the air, making it easier for the alveoli to absorb. What are the advantages of being able to breathe through your mouth as well?

13. The respiratory system

14. Summary

15. Exam-style questions • Describe the passage of oxygen from the nasal passages to the bloodstream. • This diagram shows a cross section of the respiratory system. a a) Which structures aid movement during breathing? b) Name the structures labelled a, b, c and d. b d C

16. Can you remember all these keywords? • Larynx • Trachea • Bronchus / Bronchi • Bronchioles • Alveoli • Diaphragm • Intercostal muscles