Air is conducted toward or away from lungs by series of cavities, tubes, and openings. As air moves in, it is filtered, warmed, and moistened.
Air is moistened by wet surfaces of air passages.
Two Cavities a. Nose contains two nasal cavities separated by a bone and cartilage wall. Inside nasal cavities are receptors for smell, openings for lacrimal glands and cranial sinuses . Eustachian tubes lead to middle ears from nasopharynx, the upper portion of pharynx. Trachea lies in front of esophagus , normally closed except during swallowing. Glottis is opening covered by epiglottis during swallowing of food.