Background to disease of the pharynx
The pharynx develops from the endodermal lining of the foregut. It is a fibromuscular tube that extends from the base of the skull to the lower border of the cricoid cartilage, where it is then continuous with the oesophagus. At this cricopharyngeal sphincter it is 2.5 cm (1 inch) wide — the narrowest and least dilatable part of the alimentary tract. A foreign body that passes through the cricopharyngeal sphincter is not likely to be arrested further on.