The nasal chambers open into a wide cavity called the pharynx.
It is a common path for food and air.
Prevents entry of food from into the wind pipe.
The epiglottis is a covering over the wind pipe.
If one talks during swallowing, the epiglottis is forced to open (to allow air to go outwards), and food enters the wind pipe, causing cough.

Structures involved

The pharynx-