The document summarizes respiration and the process of gas exchange that occurs in the lungs. It describes how oxygen diffuses from alveoli into the bloodstream and is transported throughout the body, while carbon dioxide diffuses in the opposite direction. It also discusses the harmful effects of air pollutants like cigarette smoke, explaining how substances like tar and nicotine can damage the lungs and lead to diseases such as emphysema, lung cancer, and heart disease.

1. RESPIRATI
ON

2. • Gas exchange in lungs is called breathing. This
exchange involves the taking in and letting out of air.

3. • 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

4. • The breathing mechanism consists of 2 phases:
• Taking in of air ------ Inhalation
• Letting out of air ---- Exhalation

5. Inhalation Exhalation
Diaphragm flattens Diaphragm arches upwards
Intercostal muscles contract Intercostal muscles relax
Ribcage moves upwards Ribcage moves downwards
and outwards and inwards
Volume of thoracic cavity Volume of thoracic cavity
increases decreases
Air pressure decreases Air pressure increases
Air flows into lungs Air is forced out of the lungs

6. Content Inhaled air Exhaled air
Oxygen 21 % 16 %
Carbon dioxide 0.04 % 6%
Nitrogen 78 % 78 %
Water vapour Variable Saturated
Temperature Variable 37º C

7. The diffusion of oxygen from the alveoli into the blood
capillaries
• Air that reaches alveoli is called alveolar air. It is rich in
oxygen and poor in carbon dioxide
• The blood that reaches the capillaries surrounding the
alveoli is poor in oxygen and rich in carbon dioxide
• Gas exchange takes place in the lungs by diffusion
• Oxygen diffuses from alveoli into red blood cells in the
capillaries
• At the same time, the red blood cells in the capillaries
release carbon dioxide which diffuses into alveoli
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8. The transport of oxygen by blood
• Red blood cells contain oxygen carrying pigment called
haemoglobin
• Oxygen combines with haemoglobin to form
oxyhaemoglobin
Oxygen + haemoglobin  oxyhaemoglobin

9. The diffusion of oxygen from the blood capillaries into the
body cells
• Oxygen has a higher concentration in the capillaries than
in body cells
• Carbon dioxide has a higher concentration in the body
cells than in capillaries
• Oxyhaemoglobin releases oxygen which diffuses into the
body cells
• Carbon dioxide diffuses into the blood at the same time

10. Substances harmful to the respiratory system
Air pollutant Harmful substances
Cigarette smoke Nicotine, tar
Gases from factories Sulphur dioxide, nitrogen
dioxide
Exhaust fumes Carbon monoxide
Haze Smoke, dust

11. Effects of harmful substances on the respiratory system
• Nicotine
• Causes addiction to cigarette smoking
• Causes rapid heartbeat, increases blood pressure and rapid
breathing
• Diseases: emphysema, heart disease and stroke
• Tar
• Contains carcinogens (substances that cause cancer)
• Irritates respiratory tract, causing ‘smoker’s cough’
• Sulphur dioxide
• Cause irritation of respiratory system
• Cause both temporary and permanent damage to lungs

12. • Carbon monoxide
• Combines haemoglobin in the blood faster than oxygen
• Poisonous gas
• Causes suffocation
• Low concentration of carbon monoxide can cause
dizziness, headaches and fatigue
• High concentration of carbon monoxide is fatal
• Particulate matter (fine particles in the air)
• Causes coughing, nasal congestion, watery nose,
constant sneezing

13. • Asthma
• Narrowing of bronchi and bronchioles due to
contraction of muscles
• Difficult to breathe, wheezing and feeling tightness in
chest
• Bronchitis
• Inflammation of lining of bronchioles due to infection by
bacteria or viruses, or chemicals found in tobacco
smoke
• Patients may turn blue especially at the lips and fingers
due to poor oxygenation of blood

14. • Lung cancer
• Emphysema
• Structure of alveoli is broken down by coughing
• Cannot take in enough oxygen and becomes very
shortness of breath.
• Heart disease
• Nicotine raises the blood pressure and increases the
level of ‘bad’ cholesterol in blood
• Suffer from stroke or heart attack