Rings of cartilage form solid support to keep an open passage in a flexible neck. 

Larynx & Epiglottis to close opening & prevent solid food from entering the trachea. 

Mucous protects epithelial cells. The mucus barrier prevents bacterial access and keeps cell moist. The mucusus is fluid so it can be swept by ciliated cells towards the pharynx for removal. Mucus is sticky so carries with it any particulate matter breathed into the airways. 

Blood supply for gas exchange.