The Journey of Your Breath: Understanding Inhalation and Exhalation

Breathing is gas exchange, not air "going" somewhere.

Inhalation

• Diaphragm contracts, chest expands → negative pressure → air enters.
• Air travels: Nose/mouth → trachea → bronchi → bronchioles → alveoli (tiny sacs, ~300M, surface area ~70 m²).
• O₂ diffuses across alveolar-capillary membrane → binds hemoglobin in RBCs.

Exhalation

• Diaphragm relaxes, chest recoils → positive pressure → air exits.
• CO₂ diffuses from blood → alveoli → exhaled.
• CO₂ is metabolic waste from cellular respiration (ATP production).

Continuous Cycle

O₂ → mitochondria → ATP + CO₂ + H₂O. CO₂ → blood → lungs → out. O₂ in → blood → cells. Continuous flow, not storage.