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What route does air follow from the nostrils to the alveoli?

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Illustration showing different animals and their respiratory organs: a spider with book lungs, a chicken with lungs, a sponge with labeled inflow and outflow pores, a fish with gills, and a caterpillar with spiracles. — Respiratory system Different methods of respiration in animals.

Air travels from the nostrils into the lungs through a branching system of conducting airways before reaching the gas-exchange zone. The general route is as follows:

Upper Airways: Air enters through the nose and passes through the pharynx, which includes the nasopharynx, oropharynx, and hypopharynx.12
Lower Airways: Air then flows into the larynx and down the trachea.32
Bronchial Tree: The trachea divides into the two stem bronchi, which branch into smaller bronchi and then into bronchioles.45
Gas-Exchange Zone: The air passes through the terminal bronchioles into the respiratory bronchioles, alveolar ducts, and finally into the alveolar sacs, where it reaches the alveoli for gas exchange.4

Throughout this journey, the conducting airways serve to warm, moisten, and clean the inspired air before it reaches the delicate tissues of the lungs.435