What is the passive component of respiration?

What is the passive component of respiration?

• A. Inhalation
• B. Diffusion
• C. Exhalation
• D. Circulation

Answer: (C)

Exhalation is the passive part of respiration. In normal, quiet breathing, air exits the lungs mainly because the lungs and chest wall recoil to their resting shape after inhalation. This recoil is elastic, so no muscles need to contract to push air out; that’s what makes exhalation the passive component. Inhalation, on the other hand, requires active muscle work as the diaphragm and external intercostals contract to expand the chest cavity and bring air in. To place this in broader context: diffusion is the process by which oxygen and carbon dioxide pass between the alveoli and blood, a gas-exchange mechanism, not a movement of air. Circulation refers to the transport of these gases through the bloodstream, also not a part of the mechanical phases of breathing.

Exhalation is the passive part of respiration. In normal, quiet breathing, air exits the lungs mainly because the lungs and chest wall recoil to their resting shape after inhalation. This recoil is elastic, so no muscles need to contract to push air out; that’s what makes exhalation the passive component. Inhalation, on the other hand, requires active muscle work as the diaphragm and external intercostals contract to expand the chest cavity and bring air in.

To place this in broader context: diffusion is the process by which oxygen and carbon dioxide pass between the alveoli and blood, a gas-exchange mechanism, not a movement of air. Circulation refers to the transport of these gases through the bloodstream, also not a part of the mechanical phases of breathing.