The normal structures and movements involved

The purpose of swallowing is to move food from the mouth to the stomach. The process is complicated by the fact that there are two channels leading downwards in the neck, one for air and the other for food and drink.   The channel for air (trachea) can be felt as a rigid structure in the front of the neck while the tube for food and fluid is behind the trachea, between it and the bones of the vertebral column. During swallowing, food and fluid have to cross the opening of the trachea without entering it. If food or fluid enter the air channel it causes coughing and is felt as “something having gone down the wrong way”, or if the quantity is large it causes choking.

During chewing the muscles of the cheeks and tongue keep the food between the teeth so that it can be crushed.  When swallowing occurs, the tongue moves the mouthful of fluid or food backwards to a funnel-shaped structure (the pharynx) which leads downwards to the upper end of the gullet (the oesophagus). At the same time the entrance to the back of the nose is closed by the soft palate and the entrance to the windpipe is closed partly by a flap and partly by muscular action.

The gullet is a flexible tube that extends approximately from the level of the “Adam’s Apple” to the right-hand side of the stomach in the upper abdomen.  It serves two functions, to transfer fluid and food downwards, and to prevent the contents of the stomach flowing upwards.  To achieve this its smooth moist inner surface is surrounded by muscle.  During swallowing waves of muscular contraction (peristalsis) pass down the gullet to push the contents along, so that it is possible to swallow successfully when the head is at a lower level than the feet.  The action of the muscle is like fingers squeezing toothpaste out of a tube.  In the upright position, food and fluid tend to pass downwards under the influence of gravity so the muscular contractions are less important.  When the gullet is empty, the lower and upper ends are kept closed by rings of muscle (sphincters).  These relax and open on swallowing to let food and fluid through into the stomach. If the lower sphincter does not close properly, stomach contents can well up into the gullet.This condition is known as reflux.