Pulmonary Ventilation

relationship among the pleura and pleural fluid

parietal pleura - lines pleural cavities

visceral pleura - covers the lungs

pleural fluid - secreted by pleura and fills the pleural space

the pleural fluid creates a fluid bond (and an associated negative Intrapleural pressure) that pulls the visceral pleura against the parietal pleura



contraction of the diaphragm

During forced breathing contraction of the external intercostal muscles, the scalenes, the sternocleidomastoid and the seratus anterior expand the thoracic cavity by elevating the ribs.



relaxation of the diaphragm and external intercostal muscles


Gas Exchange

Diffusion between alveoli and pulmonary capillaries


Oxygen Transport

Oxygen combines with hemoglobin in the blood in a reversible reaction

Hb + O2 Hb-O2


Carbon Dioxide Transport

Most carbon dioxide combines with water in the blood in a reversible reaction to form carbonic acid, that in turn dissociates in a reversible reaction to form hydrogen ions and bicarbonate ions

CO2 + H2O H2CO3 H+ + HCO3-


David G. Ward, Ph.D.  Last modified by wardd 23 May, 2006