oesophagus

oesophagus (esophagus), from the Greek for gullet, refers to the muscular tube, with a mucus-secreting lining, that leads from the mouth via the pharynx, down through the neck and the thorax, and through the diaphragm to the stomach. In the neck it lies behind the air passages — the lower end of the larynx and the upper part of the trachea. In the thorax, it continues behind the trachea and the heart, to pass into the abdominal cavity through a gap in the muscle of the diaphragm; less than an inch below this, it opens into the stomach. When swallowing occurs, food is pushed into the top of the oesophagus, and is then propelled onwards by waves of circular muscle relaxation below it and of contraction above it: the peristalsis that occurs throughout the gut. This process can if necessary defeat gravity; food, and even liquids, can be swallowed even standing on one's head, though clearly this is not generally attempted except as a remarkable demonstration. Muscle encircling the oesophagus at the top and bottom provides sphincters that, respectively, prevent air being sucked in during inhalation, and regurgitation of stomach contents.

Stuart Judge

See alimentary system; swallowing.