Exam5 Ch 21 Respiratory Fxn

• active phase • drawing in of air into lungs • diaphragm contracts and drops • size of chest cavity increases/pressure in chest cavity decreases • external intercostals contract and elevate the rib cage

principal muscle of inspiration

• passive phase: elastic recoil of muscles that were stretched during inspiration • expelling of air from lungs • diaphragm relaxes and elevates • size of chest cavity decreases/pressure in chest cavity increases • external intercostals relax and lower the rib cage

pressure inside the airways and alveoli of the lungs

pressure in the pleural cavity

pressure in the thoracic cavity

• ability to stretch • ease that lungs and thorax is expanded during inspiration • depends on elasticity of lung tissue and surface tension in the alveoli