4. If one of organ in respiration
system is unfunction, what will
happen? Explain why. ( KBAT
quest)
5. Human Breathing Mechanism
Topic 1 Respiration
THE HUMAN BREATHING MECHANISM
• Gas exchange in lungs is called breathing. This
exchange involves the taking in and letting out
of air.
6. ITeach – Science Form 3
Human Breathing Mechanism
Topic 1 Respiration
The Structure of Human Respiratory System
Trachea
Tube for air to enter into the lungs
Bronchus
Branches of trachea
Bronchioles
Branches of bronchus
Alveoli
Site of gas exchange
Diaphragm
Controls the volume in the thoracic
cavity
Intercostal muscle / rib muscle
Muscle that expands or contracts
thoracic cavity
Rib
Bones that protects the lungs
Trachea
Intercostal
Muscle
Rib
Lungs
Bronchus
Bronchiole
Alveolus
Heart
Diaphragm
7. Trachea
Rib
Intercostal
muscle
Diaphragm
Diaphragm
– Contracts
and pulls
downward
Trachea –
Carries air into
the lungs
Muscles -
Contract to
raise the
rib cage up
and
outward
Lungs –
expand
Exhaled air is
pushed out to
the trachea
Muscles –
relax and
rib cage
moves
downward
and inward
Lungs-
Shrink
Diaphragm –
relaxes and
moves up
Exhaled
air is
pushed out
through
the nostrils
ITeach – Science Form 3
Human Breathing Mechanism
Topic 1 Respiration
Breathing Mechanism
Inhalation
Inhalation
Air is taken into the lungs
Exhalation
Exhalation
Air is pushed out of the lungs.
8. ITeach – Science Form 3
Human Breathing Mechanism
Topic 1 Respiration
Comparison Between Inhalation and Exhalation
Inhalation
(Breathing in)
Exhalation
(Breathing out)
Relax ContractInternal intercostal muscles
External intercostal muscles RelaxContract
Movement of rib cage
Action of diaphragm
Volume in thoracic cavity
Air pressure in thoracic
cavity
Down and inwards
Relax
Decreases
Increases
Up and outwards
Contract
Increases
Decreases
9. ITeach – Science Form 3
Human Breathing Mechanism
Topic 1 Respiration
The Structure Of Alveolus Inside
lung
Bronchus
Bronchioles
Alveoli
10. Human Breathing Mechanism
Topic 1 Respiration
Adaptation of alveoli for efficient gas exchange
• Large surface area
– The lungs have millions of alveoli to provide a large
surface area for gas exchange
• Very thin walls
– The wall of each alveolus is one cell thick to provide a
very short distance for the diffusion of gases
• Moist inner surface
– To let oxygen dissolve in the moisture before diffusing
across the alveolar wall
• Surrounded by numerous blood capillaries
– Help to transport gases to and from alveoli quickly
11. ITeach – Science Form 3
Human Breathing Mechanism
Topic 1 Respiration
The Structure Of Alveolus
Bronchiole
Blood capillary
Alveolus
12. 1.2 Transport Of Oxygen In The Human Body
Topic 1 Respiration
ITeach – Science Form 3
13. ITeach – Science Form 3
Transport Of Oxygen In The Human Body
Topic 1 Respiration
Transportation Of Oxygen And Carbon Dioxide
Oxygen from inhaled air is
diffused into blood capillaries
through alveolus
Oxygen + haemoglobin
Oxyhaemoglobin
Oxyhaemoglobin is then
pumped to all body parts by the
heart
Meanwhile, carbon dioxide
diffuses from cells into the
capillaries.
14. ITeach – Science Form 3
Topic 1 Respiration
The Diffusion of Gases
Oxygen Exchanges
Carbon Dioxide
Exchanges
Oxygen diffuses
from alveolus to
blood capillaries
due to higher
concentration of
oxygen
Oxygen diffuses
from blood cells
into body cells due
to higher
concentration of
oxygen
Carbon dioxide diffuses
from capillary into
alveoli due to higher
concentration of carbon
dioxide in deoxygenated
blood compared to
alveoli.
Carbon dioxide diffuses
from body cells to blood
cells due to higher
concentration of carbon
dioxide in body cells
compared to blood cells.
Transport Of Oxygen In The Human Body
Red
blood
cell
Alveolus
Capillary
Oxygenated
blood
Deoxygenated
blood
Body cells
15. 1.3 The Importance Of A Healthy Respiratory
System
Topic 1 Respiration
ITeach – Science Form 3
16. ITeach – Science Form 3
The Importance Of A Healthy Respiratory System
Topic 1 Respiration
Effects Of Harmful Substances
Tar
Sulphur dioxide
Carbon monoxide
Haze
Nicotine
Cigarette smoke
Blackens and damage the internal
wall and causes cancer
Combustion of fossil
fuel
Damage lung tissues
Cigarette smoke, car
exhaust
Reduces oxygen in the blood
Excessive combustion,
open burning
Cigarette smoke
Causes irritation to respiratory tract
and breathing difficulties
Causes hardening of blood vessels
and abnormal cells growth
Harmful
Substances
Sources Effects
17. ITeach – Science Form 3
The Importance Of A Healthy Respiratory System
Topic 1 Respiration
Diseases That Affect The Respiratory System
Pnemonia
Emphyseme
Bronchitis
Tuberculosis
Asthma
Bacteria, viruses and
chemical substances
Bacteria and viruses attack the
trachea and alveolus
Alveoli expand and
burst
Destruction of alveoli
Viral infection
Cause difficulty in gaseous exchange
and respiration process
Bacterial infection
Cigarette smoke
Bacteria attacks the lungs
Tubes of the lungs become inflamed
Diseases Sources Effects
18. ITeach – Science Form 3
The Importance Of A Healthy Respiratory System
Topic 1 Respiration
Experiment To Determine The Effect Of
Cigarette Smoke On The Lungs
Green to yellow/
purple to black
Universal indicator
Temperature
Conclusion
Procedure
Observation
29°C to 33°C
Acidic substance is produced .
Heat from the smoke warms up the U-tube.
Effects Changes Discussion
Thermometer
To filter
pump
Conical
flask
Cigarette
U-tube
Cotton
Universal
indicator
Colour of cotton wool White to brownish Tar is present.
The smoke’s harmful tar and acidic substances heats and
damages our lungs.
1. Set up the apparatus as shown.
2. Switch on the filter pump to draw air
and observe the changes in
universal indicator.
19. ITeach – Science Form 3
The Importance Of A Healthy Respiratory System
Topic 1 Respiration
Ways To Improve Air Quality
Plant more trees and flowers
Walk, cycle or use public transport
Reduce the use of air conditioner
Stop open burning
Stop smoking
Car pool
