What is pulmonary ventilation (inspiration)?

Pulmonary ventilation is the process of moving air into and out of the lungs; inspiration is the phase when air enters the lungs due to diaphragm contraction.

Breathing has two phases: inspiration (inhalation) and expiration (exhalation).

Steps in inspiration

• Diaphragm contracts and moves downward.
• Intercostal muscles lift ribs upward and outward.
• Thoracic cavity volume increases, air pressure inside lungs decreases.
• Air rushes into lungs from higher to lower pressure.

Expiration

• Diaphragm relaxes; ribs move down and in.
• Lung volume decreases; air pressure increases.
• Air moves out.

Equation (simplified)

External air ⇄ alveoli ⇄ blood (gas exchange follows ventilation).