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Mechanism of Respiration

  • Respiration is the process by which the respiratory system facilitates the exchange of gases, primarily oxygen and carbon dioxide, between the body and the environment.

  • The mechanism of respiration can be divided into four main processes: ventilation, external respiration, internal respiration, and cellular respiration.

Mechanism of Respiration
Mechanism of Respiration

1.  Ventilation:

a.  Inhalation:

  • Mechanism: The diaphragm contracts and moves downward, while the external intercostal muscles lift the ribcage, expanding the thoracic cavity.

  • Effect: This increases thoracic volume, creating negative pressure that pulls air into the lungs via the respiratory tract, reaching the alveoli.

b.  Exhalation:

  • Mechanism: The diaphragm and external intercostal muscles relax, decreasing the thoracic cavity's volume.

  • Effect: This creates positive pressure, pushing air out of the lungs.

2.  External respiration:

  • Location: Alveoli and pulmonary capillaries.

  • Mechanism: Oxygen diffuses from the air in the alveoli into the blood, binding to hemoglobin in red blood cells.

  • Simultaneously: Carbon dioxide diffuses from the blood into the alveoli to be exhaled.

3.  Internal respiration:

  • Location: Systemic capillaries and body tissues.

  • Mechanism: Oxygen-rich blood from the lungs is pumped through systemic circulation.

  • Oxygen diffuses from the blood into tissues, while carbon dioxide produced by cells diffuses into the blood.

  • The carbon dioxide-rich blood returns to the lungs via the right side of the heart.

4.  Cellular respiration:

  • Location: Mitochondria in cells.

  • Mechanism: Cells use oxygen to produce ATP (energy) through glycolysis, the citric acid cycle, and the electron transport chain.

  • By-product: Carbon dioxide is produced and transported back to the lungs for elimination..


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