What is the function of a frog's glottis?

The glottis is responsible for the vocalizations a frog makes. It is the combination of vocal folds and the space between each fold.

The glottis is the entrance to the larynx. These organs work together to give the frog its unique vocalizations and sounds. As the folds vibrate, they produce a buzzing sound. Those animals that can produce sounds using only the glottis, and don't have a larynx, are called glottal animals. It produces sound by creating friction.

Amphibians, reptiles and mammals have a glottis, which is also used in breathing and protecting the trachea against food that may get stuck in the throat.