Mechanism of breathing, respiratory organs in humans, gas exchange

1. Introduction to the Respiratory System

1. The respiratory system is responsible for the exchange of oxygen (O₂) and carbon dioxide (CO₂) in the body.
2. It ensures oxygen supply to the cells for energy production and removes carbon dioxide as a waste product.
3. The primary processes involved are breathing, gas exchange, and cellular respiration.

2. Respiratory Organs in Humans

1. Nasal Cavity: Filters, moistens, and warms incoming air.
2. Pharynx: A common passage for both air and food.
3. Larynx: Known as the voice box, contains vocal cords.
4. Trachea: A windpipe lined with mucus and cilia to trap dust and microbes.
5. Bronchi: Two tubes that branch from the trachea into each lung.
6. Bronchioles: Smaller airways that distribute air within the lungs.
7. Alveoli: Tiny air sacs where gas exchange occurs.
8. Diaphragm: A muscular structure that aids in breathing.

3. Mechanism of Breathing

(a) Inhalation (Inspiration)

1. The diaphragm contracts and moves downward.
2. Intercostal muscles contract, expanding the ribcage.
3. Volume of the chest cavity increases, reducing pressure inside the lungs.
4. Air rushes into the lungs due to the pressure difference.

(b) Exhalation (Expiration)

1. The diaphragm relaxes and moves upward.
2. Intercostal muscles relax, causing the ribcage to move downward.
3. Volume of the chest cavity decreases, increasing pressure inside the lungs.
4. Air is pushed out of the lungs.

4. Gas Exchange in the Lungs

1. Occurs in the alveoli, where oxygen and carbon dioxide are exchanged between the lungs and blood.
2. Oxygen diffuses from alveolar air into the blood.
3. Carbon dioxide diffuses from blood into the alveoli to be expelled.
4. The exchange process follows the principle of diffusion (movement from high to low concentration).
5. Hemoglobin in red blood cells binds with oxygen to form oxyhemoglobin.
6. Carbon dioxide is transported in three forms: dissolved in plasma, bound to hemoglobin, or as bicarbonate ions.

5. Transport of Gases

1. Oxygen Transport: Carried by hemoglobin in red blood cells.
2. Carbon Dioxide Transport: 70% as bicarbonate ions (HCO₃⁻), 20% bound to hemoglobin, and 10% dissolved in plasma.

6. Regulation of Breathing

1. Controlled by the medulla oblongata in the brain.
2. Chemoreceptors detect carbon dioxide levels and adjust breathing rate.
3. High CO₂ levels lead to increased breathing rate to remove excess CO₂.

7. Common Respiratory Disorders

1. Asthma: Inflammation of airways leading to breathing difficulty.
2. Bronchitis: Infection or irritation causing inflammation of the bronchi.
3. Pneumonia: Infection leading to fluid accumulation in alveoli.
4. Emphysema: Damage to alveoli causing reduced oxygen intake.
5. Tuberculosis (TB): A bacterial infection affecting the lungs.

8. Summary of Breathing and Gas Exchange

9. Conclusion

1. The respiratory system plays a vital role in oxygen intake and carbon dioxide removal.
2. Gas exchange at the alveoli is essential for cellular respiration.
3. Proper lung function ensures efficient energy production and metabolism.
4. Maintaining lung health through exercise and avoiding pollutants is crucial.