Key Terms
Primary function
Deliver O2 to body cells; remove CO2 waste. Gas exchange is driven entirely by diffusion — molecules moving from high co
Everything in this chapter builds on two rules
1. Gases move down their concentration/pressure gradient.
Result
Persistent cough and increased infection risk. The system designed to protect the lung gets turned against it.
KEY DISTINCTION
Volume = one function (one inhale or exhale). Capacity = two or more volumes added together.
WHY THIS MATTERS - RV and stability
The residual volume also prevents large swings in O2 and CO2 levels between breaths. It's a buffer, not dead weight.
Partial pressure
Pressure of one gas in a mixture; drives direction of gas diffusion.
INHALATION (active process)
1. Diaphragm contracts → moves downward 2.
EXHALATION (passive process)
1. Diaphragm relaxes → moves upward 2.
Visceral pleura
Covers the lung surface. Parietal pleura: lines the interior thoracic wall.
Pleurisy
Inflammation of pleural layers → increased pressure in thoracic cavity → reduced lung volume → painful breathing.
Surfactant
Phospholipid/lipoprotein mixture; reduces alveolar surface tension; prevents collapse.
Respiratory distress syndrome
Premature infants don't produce enough surfactant → lungs require enormous effort to inflate → breathing failure.
Compliance
Lung elasticity; decreased in restrictive disease; increased in emphysema.
Ideal
V and Q match. Gas exchange is maximal.
Anatomical dead space (anatomical shunt)
Structural failure. Example: standing upright; gravity pulls more air to the bottom of the lungs, but perfusion is also