Comparative Vertebrate Physiology Physiology of air breathing The lungs

Respiration Oxygen utilization varies with activity Rest: 200 ml/min. Exercise: 6,000 ml/min. O2 utilization depends on metabolic demands pH regulation of ECF

Organization Conducting zone Respiratory zone

Functions of pathway Conducting zone Warm, cleanse and humidify air Phonation (vocal cords) Regulation of air flow

Functions of pathway Respiratory zone Gas exchange

Functions of pathway Cell type I (gas exchange) Cell type II (surfactant)

Gas Exchange Gases must penetrate 3 areas 1 2 3

Diffusion distances Shorter is better (µm) Animal Diffusion distance (ｵm) Toad Birds pigeon swallow shrike Mammals rat human shrew 1.3 - 3.0 0.1 - 1.4 0.09 0.17 0.13 - 0.26 0.36 - 2.5 0.27 (µm)

Lung ventilation Closed compartment Pleura Head, diaphragm, sternum, ribs and intercostal muscles Pleura Parietal (chest) Visceral (lungs) Pleural fluid

Ventilation steps Exchange of air between atm. and alveoli Ventilation, bulk flow Exchange of O2 and CO2 between alveoli and lung capillaries Diffusion Transport of gases by blood Bulk flow Exchange of gases between blood and tissues

Ventilation

Ventilation What pressure changes? Ans: alveolar Bulk flow: F = K (∆P) How does pressure change? Intrapleural vs. intrapulmonary pressure

Ventilation Intrapleural pressure Tendency of lung recoil Surface tension of alveolar fluid Opposed by chest wall elasticity Intrapleural pressure Intrapulmonary pressure

Ventilation Balloon within a balloon

Ventilation

Air flow Flow (F) = ∆P/R ∆P: change in pressure between atmosphere and alveoli R: resistance of airways

Air flow ∆P: altered by contraction of inspiratory and expiratory muscles Resistance Inversely proportional to 4th power of radius A B

Measuring lung volumes Respirometer

Respirometry data

Dead space