Immunological defenses of the suckling infant - milk
When an infant suckles at the breast, milk may very well trickle into the trachea and coat the lining with a layer of powerful antibacterial medicines : antibodies. When we think it is quite fascinating how design of the epiglottis permits simultaneous opening of adjacent passageways which are one-or-the-other in the adult human, it seems patently wonderful to think of this added benefit!
Especially more helpful given the immunological naivete of the infant's native defenses. Marvelously made!