Editing Oesophagus (section)

=== '''Lower     oesophageal sphincter''' - 38-40cm from teeth ===

** More of a physiological      sphincter/zone of high pressure (mean pressure 24mm Hg)
** See below under physiology      of swallowing
** Made up of four anatomic      structures:
*** Intrinsic musculature of       the distal oesophagus - muscle fibres relax as part of swallowing, then       return to a state of tonic contraction
*** Sling fibres of the gastric       cardia - oriented diagonally from the cardia-fundus junction to the       lesser curve of the stomach, located at the same anatomic depth as the       circular muscle fibres of the oesophagus
*** The crura of the diaphragm       - contracts during inspiration to counter the intra-thoracic pressure       differentiation
*** Increased intra-abdominal       pressure, which is transmitted to the GOJ, increasing the pressure on       the distal oesophagus and preventing spontaneous reflux of gastric       contents
** Can be identified by two      endoscopic and two external features:
*** Z-line (squamocolumnar       junction)
*** GOJ: transition from smooth       oesophageal lining to rugal folds of stomach
*** Collar of Helvetius/loop of       Willis - where circular muscular fibres of the oesophagus join the       oblique fibres of the stomach (externally)
*** Gastro-oesophageal fat pad       (externally)
***

*

*