Question

What part of the Gl tract prevents a person from choking while swallowing?

Answer 1

Epiglottis.

Explanation:

Larynx also known a voice box has a flap over it which is made of cartilage and covered with a mucous membrane. This flap is called epiglottis . Epiglottis acts like a lid. It is muscularly controlled structure. It shows hinge like action.
In a nutshell, epiglottis is a structure in respiratory tract which automatically closes the opening of larynx during the act of swallowing. Thus it prevents the food from entering the wind pipe or trachea. Consequently, it prevents choking.

Hope it helps...