1. the introduction of air into the body-cavity-Rouge > anal mucus from nose (nasal cavity) throat (pharynx), the voice box (larynx) neck, windpipe (trachea), lungs, trachea or windpipe pole (bronchus) and FOI (bronchiole)
2. where gas exchange occurs--> windpipe opening gas exchange resembles a small bags (pulmonary-alveoli), which can cause gas exchange