AETIOLOGY. The upper end of the oesophagus is guarded by a muscle sphincter
called the cricopharyngeus which is normally closed. The lower part of the
pharynx has a weak area at the lower part of the inferior constrictor muscleŚ
the so-called dehiscence of Killian (Fig. 115). At this point there is only a
mucosal layer, a submucosa and one layer of muscle fibres. If the patient has
the habit of a 'double swallow' and develops an abnormally high intra-
pharyngeal pressure during swallowing then this weak area will be subjected
Fig. 113. Shows spoon-shaped, brittle nails
in the Paterson-Brown Kelly syndrome.
Fig. 114. Radiograph to show the Paterson-
Brown Kelly syndrome with web.
Fig. 115. A ,Site of origin of pouch between oblique and transverse cricopharyngeus; B, Cricopharyngeal