Which structure allows air to flow safely into the lungs after leaving the nasal cavity?

After the nasal cavity, the air passes through the pharynx or throat and the larynx, also known as voice box as it makes its way to the trachea, which serves as a funnel for the inhaled and the exhaled air of the body. Then, air continue to flow at the end of the trachea where it is divided into two bronchi that enter the right and left lung. This primary bronchus splits, creating smaller and smaller diameter until they are called bronchioles as they fragmented and spread through the lung. 

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