Breathing and Exchange of Gases - Class 11 (Short
Notes)
Breathing and exchange of gases is the biological process where oxygen is taken in and carbon
dioxide is released. It involves the respiratory organs, breathing movements, transport of gases,
and regulation of respiration.
1. Human Respiratory System
• Major parts: Nostrils, Pharynx, Larynx, Trachea, Bronchi, Lungs. • Lungs are the primary organs of
respiration with alveoli for gaseous exchange.
2. Breathing (Ventilation)
• Inspiration: Inflow of air due to diaphragm contraction and rib cage expansion. • Expiration:
Outflow of air due to relaxation of diaphragm and ribs moving down.
3. Exchange of Gases
• Occurs at two levels: - External respiration: Between alveoli and blood. - Internal respiration:
Between blood and tissues. • O■ diffuses into blood, CO■ diffuses out due to pressure gradients.
4. Transport of Gases
• Oxygen transport: 97% carried by hemoglobin as oxyhemoglobin; 3% dissolved in plasma. •
Carbon dioxide transport: 70% as bicarbonate ions, 23% as carbamino-hemoglobin, 7% dissolved
in plasma.
5. Regulation of Respiration
• Controlled by respiratory centers in medulla oblongata and pons. • Chemoreceptors detect CO■
and H■ concentration, influencing breathing rate.
6. Disorders of Respiratory System
• Asthma: Difficulty in breathing due to inflammation of bronchi. • Emphysema: Damage to alveolar
walls. • Occupational lung diseases: Due to inhalation of harmful dusts (silicosis, asbestosis).
Notes)
Breathing and exchange of gases is the biological process where oxygen is taken in and carbon
dioxide is released. It involves the respiratory organs, breathing movements, transport of gases,
and regulation of respiration.
1. Human Respiratory System
• Major parts: Nostrils, Pharynx, Larynx, Trachea, Bronchi, Lungs. • Lungs are the primary organs of
respiration with alveoli for gaseous exchange.
2. Breathing (Ventilation)
• Inspiration: Inflow of air due to diaphragm contraction and rib cage expansion. • Expiration:
Outflow of air due to relaxation of diaphragm and ribs moving down.
3. Exchange of Gases
• Occurs at two levels: - External respiration: Between alveoli and blood. - Internal respiration:
Between blood and tissues. • O■ diffuses into blood, CO■ diffuses out due to pressure gradients.
4. Transport of Gases
• Oxygen transport: 97% carried by hemoglobin as oxyhemoglobin; 3% dissolved in plasma. •
Carbon dioxide transport: 70% as bicarbonate ions, 23% as carbamino-hemoglobin, 7% dissolved
in plasma.
5. Regulation of Respiration
• Controlled by respiratory centers in medulla oblongata and pons. • Chemoreceptors detect CO■
and H■ concentration, influencing breathing rate.
6. Disorders of Respiratory System
• Asthma: Difficulty in breathing due to inflammation of bronchi. • Emphysema: Damage to alveolar
walls. • Occupational lung diseases: Due to inhalation of harmful dusts (silicosis, asbestosis).
