Respiratory System Functions - Ventilation: Mechanical act of breathing - External respiration - Exchange of gases between the atmosphere and the blood - Internal respiration - Exchange of gases between blood and cells of the body Air - 78% Nitrogen - 21% Oxygen - less than 1% Carbon Dioxide Inspiration: Contraction of the diaphragm Expiration: Relaxation of the diaphragm Lung Volumes - Tidal volume: Normal, at-rest breathing - Inspiratory reserve volume – taking a very deep breath - Expiratory reserve volume – exhale forcefully after normal at rest exhalation - Residual volume – air remaining after expiratory reserve volume exhaled - Vital capacity – inspiratory reserve volume and tidal volume and expiratory reserve volume - Total lung capacity – vital capacity and residual volume Compliance and Elastance - Compliance: ability to stretch - High compliance - Stretches easily - Low compliance - Requires more force - Restrictive lung diseases - Fibrosis - Inadequate surfactant production - Elastance: Ability to return to resting volume when stretching force is released Surfactant - Makes lungs more compliant - More concentrated in smaller alveoli - Newborn respiratory distress syndrome - Premature babies - Inadequate surfactant concentrations