1. Mechanisms of breathing

2. What you will learn about
Mechanisms of breathing 2
What you will learn about
in this topic:
The function of the respiratory system
The mechanisms of breathing
The role of the lungs
Alveoli
Composition of air inhaled and exhaled

3. Mechanisms of breathing 3
Learning objectives
By the end of this presentation you should be able to:
Understand the function of the respiratory system
Describe the effects of exercise on breathing
Explain what happens when you breathe

4. The function of the respiratory system
Mechanisms of breathing 4
The function of the
respiratory system
The function of the respiratory system is to get oxygen into the body and carbon dioxide and waste products from metabolism out of the body.

5. Mechanisms of breathing 5
This happens through the act of breathing. Breathing in (inhalation) gets the oxygen in, so it can be used by the body to release energy.
Breathing out (exhalation) removes the carbon dioxide so it does not build up and poison the body.

6. The following are all parts of the respiratory system: Air passages
Mechanisms of breathing 6
The following are all parts of the respiratory system:
Air passages
Lungs
Diaphragm

7. Composition of inspired
Mechanisms of breathing 10
Composition of inspired
and expired air
The air we breathe in is very different from the air we breathe out.
The parts that make up inhaled and exhaled air are called its composition.

8. Percentage of air inhaled:
Mechanisms of breathing 11
Percentage of air inhaled:
Key
Nitrogen
Oxygen
Carbon dioxide
Other

9. Percentage of air exhaled:
Mechanisms of breathing 12
Percentage of air exhaled:
Key
Nitrogen
Oxygen
Carbon dioxide
Other

10. The link between respiration
Mechanisms of breathing 13
The link between respiration
and circulation
Oxygen goes from the respiratory system to the circulatory system and then back to the respiratory system.

11. Mechanisms of breathing 14
Oxygen breathed in goes through the mouth or nose, down the trachea, into the lungs and into the alveoli.

12. Oxygen joins with haemoglobin to make oxyhaemoglobin.
Mechanisms of breathing 15
Oxygen then passes through the alveoli walls into the red blood cells, via the capillaries.
Oxygen joins with haemoglobin to make oxyhaemoglobin.
The oxyhaemoglobin is used by the working body and is transported by the circulatory system to cells needing to release energy.

13. Mechanisms of breathing 16
Carbon dioxide is produced as a waste product. This is converted into a gas and passes back through the alveoli walls, via the capillaries into the blood plasma.
The carbon dioxide passes through the capillary and alveoli walls into the alveoli. It is then exhaled from the body.

14. Parts of the respiratory system
Mechanisms of breathing 17
Parts of the respiratory system

15. The mechanism of breathing
Mechanisms of breathing 18
The mechanism of breathing
Lungs are not muscle, cannot move of their own accord and are not controlled by the central nervous system.
The key to breathing is the diaphragm and the intercostal muscles between the ribs.
Expiration

16. When we breathe in (inspiration) the following happens:
Mechanisms of breathing 19
When we breathe in (inspiration) the following happens:
The diaphragm pulls down
The intercostal muscles contract
Air pressure is reduced
Air is sucked through the tubes into the lungs
The chest expands.

17. Mechanisms of breathing 20

18. When we breathe out (expiration) the opposite happens:
Mechanisms of breathing 21
When we breathe out (expiration) the opposite happens:
The diaphragm relaxes into its dome position
The intercostal muscles relax
The chest becomes smaller
Pressure increases in the lungs
Air is forced out

19. Mechanisms of breathing 22

20. Mechanisms of breathing 23
Task 1
In groups of four, write 13 statements on 13 pieces of card (one on each card) about the route of oxygen and carbon dioxide around the body.
Put your cards in order, starting and ending with a card marked ‘Oxygen is inhaled’.
Teacher’s notes
Possible answers are given on slides 24 to 27.

21. Possible answers to Task 1
Mechanisms of breathing 24
Possible answers to Task 1
Oxygen passes through the larynx and trachea.
Oxygen arrives in the lungs via the bronchi and bronchioles.
Oxygen passes to the alveoli and transfers to the haemoglobin through the plural membrane

22. The heart pumps the blood through the aorta to the arteries.
Mechanisms of breathing 25
The haemoglobin in the red blood cells binds with the oxygen to become oxyhaemoglobin.
The blood travels through the pulmonary vein to the left side of the heart.
The heart pumps the blood through the aorta to the arteries.
The arteries carry the oxygenated blood around the body.

23. The veins carry the deoxygenated blood.
Mechanisms of breathing 26
The haemoglobin releases the oxygen at the muscles and collects the carbon dioxide; the blood is now considered deoxygenated.
The veins carry the deoxygenated blood.
The deoxygenated blood arrives at the heart.

24. The carbon dioxide passes through the trachea and is exhaled.
Mechanisms of breathing 27
The heart pumps the deoxygenated blood back to the lungs via the pulmonary artery.
The carbon dioxide passes across the pleural membrane and into the alveoli.
The carbon dioxide passes through the trachea and is exhaled.

25. Mechanisms of breathing 28
The role of the lungs
The lungs are positioned inside the chest cavity and are protected by the ribcage.

26. The pleural membrane is smooth and has a moist, slimy mucus.
Mechanisms of breathing 29
The action of breathing means that the lungs are constantly moving in and out. To protect them from any friction due to the movement, the pleural membrane forms a complete lining around them.
The pleural membrane is smooth and has a moist, slimy mucus.

27. Alveoli Alveoli are tiny air sacs at the end of the bronchioles.
Mechanisms of breathing 30
Alveoli
Alveoli are tiny air sacs at the end of the bronchioles.

28. There are millions of them that allow gases to exchange inside them.
Mechanisms of breathing 31
There are millions of them that allow gases to exchange inside them.
Oxygen passes across the pleural membrane and into the blood. Carbon dioxide passes from blood to the alveoli.

29. Here is a simplified version of what happens:
Mechanisms of breathing 32
Here is a simplified version of what happens:
Oxygen from the air breathed in enters the circulatory system to be used by the working muscles.

30. Mechanisms of breathing 33
Carbon dioxide, which is toxic to the system, transfers from the used blood, out of the circulatory system, back into the alveoli, to be breathed out along with oxygen, water and nitrogen.

31. Mechanisms of breathing 34
The capillaries, covering the surface of the alveoli, link the respiratory system with the circulatory system.
Regular exercise conditions the lungs to excrete more of the carbon dioxide from the body.

32. Mechanisms of breathing 35
Tidal volume is the amount of air breathed in and out of the body during normal breathing.
During exercise, the volume is forced to change. It is then called forced breathing.

33. Mechanisms of breathing 36
Vital capacity is the largest amount or volume of air that can be exhaled after the largest possible inhalation.
Residual volume is the amount of air that, even after as much air as possible has been exhaled, is left in the lungs.

34. Mechanisms of breathing 37
Task 2
In groups of four, describe the action of breathing using the following words to help you:
Nose
Mouth
Trachea
Lungs
Ribs
Intercostal muscles
Diaphragm
Teacher’s notes
Possible answers are given on slide 38.

35. Possible answers to Task 2
Mechanisms of breathing 38
Possible answers to Task 2
From the nose or mouth, air enters the trachea and moves towards the lungs.
The trachea divides into two branches called the bronchi. These sub-divide into smaller tubes called bronchioles.
During heavy exercise the body uses the intercostal muscles between the ribs to aid the diaphragm in the exhalation of air from the lungs.
At the end of the bronchioles are alveoli.
Alveoli are air sacs with many tiny blood vessels called capillaries running from them.

36. Explain the process of inspiration.
Mechanisms of breathing 39
Exam questions
Explain the process of inspiration.
Explain the process of expiration.

37. What you have learnt about
Mechanisms of breathing 40
What you have learnt about
in this topic:
The function of the respiratory system
The mechanisms of breathing
The role of the lungs
Alveoli
Composition of air inhaled and exhaled

38. Learning objectives You should now be able to:
Mechanisms of breathing 41
Learning objectives
You should now be able to:
Understand the function of the respiratory system
Describe the effects of exercise on breathing
Explain what happens when you breathe