Human Anatomy and Physiology Physiology of air breathing The lungs

Respiration Oxygen utilization varies with activity Rest: 200 ml/min. Exercise: 6,000 ml/min. Importance Breathing increases due to metabolic demands Regulated by pH of ECF

Organization Conducting zone Trachea, 1° - 3° bronchi Respiratory zone Bronchioles, alveolar ducts alveoli Trachea 1° 2° 3° brochioles Alveolor ducts alveoli

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

Functions of pathway Respiratory zone Gas exchange

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

Gas Exchange Gases must penetrate 3 membranes

Diffusion distances Shorter is better

Lung ventilation Closed compartment 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 O 2 and CO 2 between alveoli and lung capillaries Diffusion Transport of gases by blood Bulk flow Exchange of gases between blood and tissues Diffusion

Ventilation

What pressure changes? Ans: alveolar pressure Bulk flow: F = K (∆P) How does pressure change?

Ventilation Cavities Pleural, pulmonary Intrapleural pressure. Why have it? Tendency of lung recoil Surface tension of alveolar fluid Opposed by chest wall elasticity Intrapulmonary pressure Balloon within a balloon

Ventilation Expiration Inspiration

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

Air flow Lung compliance V = change in volume P = change in pressure V P Athletes have a high lung compliance

Lung volumes Respirometer

Lung volumes

Dead space Anatomical dead space Alveolar dead space (inspired dead space) Total dead space