Final answer:
The structure that directs food to the oesophagus and air to the trachea is the larynx. Air travels from the pharynx to the bronchioles in the sequence: pharynx → larynx → trachea → bronchi → bronchioles. The alveoli are the structures found in the lungs where gas exchange occurs.
Step-by-step explanation:
The structure that channels food to the oesophagus and air to the trachea is the larynx. When we swallow, a small flap called the epiglottis covers the trachea to ensure that food enters the oesophagus and not the airway. During breathing, the epiglottis stays open, allowing air to pass from the pharynx to the larynx and then into the trachea, which leads to the lungs.
Regarding the order in which inhaled air travels from the pharynx to the bronchioles, the correct sequence is: pharynx → larynx → trachea → bronchi → bronchioles. Therefore, the bronchioles branch into bronchi and not the other way around, and gas exchange takes place in the tiny air sacs called alveoli.