The presentation summarizes the key components and functions of the human respiratory system. It describes the pathway of air from the nose through the nasal cavity, pharynx, trachea, bronchi and bronchioles to the lungs. It explains the mechanical process of breathing including inspiration and expiration powered by the diaphragm and intercostal muscles. Gas exchange occurs in the lungs as oxygen enters the bloodstream and carbon dioxide leaves. Homeostatic control maintains proper blood pH levels. Inspired air contains 21% oxygen while expired air contains less oxygen and more carbon dioxide after gas exchange.

1. Presentation by Ntokozo Zwane
GRADE 11
HUMAN
VENTILATION
SYSTEM

2. The structure,
location, adaptations
and functions of the
human ventilation
system.
Mechanical process
of ventilation
The composition of
inspired air versus
expired air.

3. 


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5. Gas exchange: oxygen enters blood and carbon
dioxide leaves.
Regulation of blood pH: altered by changing blood
carbon dioxide levels.
Voice production: movement of air past vocal folds
makes sound and speech.
Olfaction: smell occurs when airborne molecules drawn
into nasal cavity.
Protection : against microorganisms by preventing
entry and removing them.
(Sunil, 2018).

6. The structure and location
Source by: CBSE. Link: https://www.topperlearning.com/answer/where-does-the-exchange-of-
gases-take-place-in-the-human-respiratory-system-draw-a-neat-and-labelled-diagram-of-the-
human-respirat

8. Nasal passage, pharynx, trachea,
bronchi, bronchiole.
(SEER Training Modules, 2021)
Transports air to and from the lungs.

9. Two external nostrils lead to
two nasal cavities that are
separated by the two septum.
The nasal cavity has small
hairs which filter foreign
particles from inhaled air.
Each nasal cavity divide into 3
passages.

10. Cont.
The nasal cavity has small hairs which filter particles from
inhaled air.
It is also lined with a mucus membrane which consist of
epithelial cells.
Epithelial cells are composed of goblet cells which secret
mucus that traps dust and germs from multiplying.
Cilia: hairs which sweep the movement of dust-carrying
mucus so that it can be expelled outside (Mzoury, 2016).

11. Pharynx (throat)
The nasal cavity will open into the
pharynx. Leading to two openings.
Epiglottis leading to the trachea.
Second opening leading to the
oesophagus (Kaylie, 2019).

12. Trachea(windpipe)
 It is a long tubular structure located
in front of the esophagus.
 Lined by pseudostratified ciliated
columnar epithelium
(Eneutron,2017).
 Larynx (voice box) located at the
top of the trachea.
Source from: Richard.

13. Bronchi and
Bronchiole (GCSE, 2021)
Trachea divides into
2 bronchus leading
to:
Left lung
Right lung
Bronchi is lined with
mucus membrane
and held open by O-
shaped rings.
Inside the lungs,
bronchi divides into
smaller branches
called bronchioles.

14. •
•
•

15. Process of
ventilation/
Mechanism of
Breathing.
 Breathing or ventilation is the movement
of air going in and out of the lungs.
 This movement is brought about by two
muscles:
 Intercoastal muscles
 Muscles in the diaphragm.

16. Cont.
 The process of breathing
consists of 2 phases:
 Inspiration (Inhalation)
 Exhalation (Expiration)
(Rich,
2017).

17. The flow of air into the
lungs.
The diaphragm
contracts and
flattens.
Increasing the volume
of the thorax from top
to bottom.
Intercoastal muscles
contract
Causing the ribs to be
lifted upwards and
outwards.
Interpleural pressure
decreases ( pressure
between pleura)
Due to the decrease
of pressure in lungs.

18. The flow of air out
of the lungs.
Diaphragm
relaxes and
becomes dome-
shaped.
This decreases the
volume of the
thorax from top to
bottom.
External
intercoastal
muscles relax.
The rip cage lowers
and becomes
smaller.
The volume in the
thorax decrease
sideways.
Interpleural
pressure
increases.
Increases pressure
in the lungs.
Forcing the air out
of the lungs.

19. You might want to think twice
about smoking…..
(source from: Richard Hartley-Parkinson)
https://metro.co.uk/2018/05/02/nurse-shares-showing-just-bad-smoking-affects-
lungs-7514050/

20. Homeostatic control of breathing
The rate of breathing is determined by the level of carbon
dioxide on blood and not the level of oxygen.
Carbon dioxide dissolves in the blood to form carbonic acid,
which lowers the blood pH
Any changes in Ph levels are detected, corrected and returned
to normal level through negative feedback.
(Sacklax, 2018).

21. Chemoreceptors in the medulla oblongata (brain) ,
the aorta and the carotid arteries detect increases in
blood pH levels.
Impulses are sent to stimulate medulla oblongata to
the diaphragm and the intercoastal muscles to
stimulate contraction.
This causes the rate of inhalation and exhalation to
increase.
When the blood pH returns to normal, the rate of
breathing also returns to normal.
(Mzoury,2016) .

22. Composition of inspired air
and expired air
Nitrogen is not absorbed into the blood; there the
percentage stays the same.
• ±4% of Oxygen is absorbed in the blood and ±4% of
Carbon dioxide is expelled.
• More Carbon dioxide is exhaled than inhaled.
• (Pfizer, 2013).

23. Summary (Pfizer, 2013).
GAS PERCENTAGE OF
INSPIRED AIR
PERCENTAGE OF
EXPIRED AIR
Oxygen 21% 14,5%
Carbon dioxide 0,04% 4%
Nitrogen 78% 78%
Water vapour 1,6% 6.2%

24. References
(n.d.). Retrieved August 21, 2021, from GCSE Biology.
Chavda, M. (2018). Available from Slideshare at
https://www.slideshare.net/sunilkumar1153/respiratory-system-physiology-of-respiratory-system-
and-neural-control?qid=84c5f94a-c3fa-426b-b3e6-cc08af28896e&v=&b=&from_search=4t
(Accessed 21 August 2021).
Dreamstime.com. (n.d.). The diaphragm. Retrieved August 16, 2021.
Eneutron. (2017). Respiratory System. Available on Slideshare at
https://www.slideshare.net/E_neutron/respiratory-system-77449137?qid=4b969c6b-09b5-4d6c-
905b-22c2d0d5ee10&v=&b=&from_search=2. (Accessed 16 August 2021).
Imondi, K. (2018). Retrieved August 16, 2021, from Pintrest.
Kaylie, D. M. (2019). Nose cavity diagram. Retrieved August 21, 2021.
Kumar, S. (2018). Respiratory system. Available from Slideshare at
https://www.slideshare.net/sunilkumar1153/respiratory-system-physiology-of-respiratory-system-
and-neural-control?qid=84c5f94a-c3fa-426b-b3e6-cc08af28896e&v=&b=&from_search=4 Retrieved
August 16, 2021. (Accessed 16 August 2021).

25. Mzoury, R. (2016). Respiratory system. Available from Slideshare at
https://www.slideshare.net/RayanMzoury/1-respiratory-system-
61035273?qid=6baf2e54-d676-4769-9cfc-fde9bf2c86f2&v=&b=&from_search=150.
(Accessed16 August 2021).
Pfizer. (2013). Respiratory system ppt. Available from Slideshare at
https://www.slideshare.net/Sanzux/final-ppt-of-respiratory. (Accessed 21 August 2021).
Rich, A. (2021, August 16). Knowswhy.com . Retrieved from Difference between inhalation
and exhalation.
Richard, H. (2021, August 5). Retrieved August 16, 2021, from en. wikipedia.org.
Sacklax. (2018). Homeostatic control of breathing. Available from Slideshare at
https://www.slideshare.net/sacklax40/respiratory-system-presentation?qid=8931b4bb-
fd23-4d4c-bb82-7ace595f72dd&v=&b=&from_search=1. (Accessed 21 August 2021).
SEER Training Modules. (2021). Air passages diagram. Retrieved August 16, 2021.
Shutter.com. (n.d.). Retrieved August 16, 2021.

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