[@The Grey Dust] Um, doesn't matter. It's the same tube at the top anatomically...[url=http://m.newhealthadvisor.com/images/1HT02960/what%20keeps%20food%20down%20the%20stomach.jpg]Image Diagram[/url] 

There is a flap of muscle that closes over one side when you swallow to protect the bronchial tubes and keep things going into the lungs. O.o Tilting the head back doesn't close that off, if anything it stretches it open more, why it is part of the instructions before delivering CPR or to insert a breathing tube. Swallowing is a conscious decision that closes the epiglottis, other wise it stays open so breathing can remain.