Dead Space Volume of inhaled air which does not take part in gas exchange • Anatomical dead space : Volume of conducting respiratory passageways (150 mL) • Alveolar dead space : Volume occupied by alveoli that cease to act in gas exchange (due to collapse, obstruction or lack of adjacent pulmonary capillaries) • Total dead space = Anatomical + Alveolar dead spaces
Dead Space • Healthy lungs: small alveolar dead space • Certain lung diseases : increase in alveolar dead space Emphysema Chronic obstructive pulmonary disease (COPD) Pneumonia Bronchitis
Non-respiratory Air Movements Most result from reflex actions Coughing Sneezing Crying Laughing Yawning
Composition of Alveolar Gas • Atmosphere contains mostly oxygen & nitrogen • Alveoli contain more carbon dioxide & water vapor • Gas exchanges in lungs • O 2 diffuses away from alveoli & CO 2 diffuses into alveoli • Air is humidified by conducting pathways
Key Points Inspiration Diaphragm & external intercostal muscles contract Intrapulmonary volume increases Intrapulmonary pressure drops Air flows into lungs Expiration Inspiratory muscles relax Intrapulmonary volumes decreases Intrapulmonary pressure rises Gases flow out of lungs Forced Inhalation & Expiration Lung Volumes & Capacities Dead Space • Anatomical dead space • Alveolar dead space Non-respiratory Air Movements
You've reached the end of your free preview.
Want to read all 46 pages?
- Fall '19