Epiglottis

Cartilaginous, flap-like structure that prevents the entry of food into the larynx (see figure below).  In the human newborn, the entrance to the larynx is above the level of the tongue, which means it is possible to drink and breath at the same time.  Within the next six months, the epiglottis descends in the pharynx in order to close off the trachea, and with this it is no longer possible to breath while drinking. 

See Larynx, Newborn, Pharynx