Read the section headed 'In the esophagus' in this Wikipedia article about peristalsis:
http://en.wikipedia.org/wiki/Peristalsis
That shows what's meant to happen when you swallow something. However this 1981 study (by Meyer & Castell) found that the muscular 'waves' in your oesophagus, which should push food and liquids along it, can be...
20:14 Fri 21st May 2010