Editing Oesophagus (section)

== '''Gross anatomy''' ==

=== '''Relations:''' ===

** '''Pleura'''
*** On the right, full length       of oesophagus is against pleura, except where azygos comes forward to       join SVC
*** On the left, aortic arch       separates oesophagus from pleura superiorly; lower down, oesophagus is       in direct contact with pleura
*** Posterior to lower thoracic       oesophagus, the two pleural cavities almost touch
** '''Vagus      nerves'''
*** Come into contact below       carina
*** Note form plexus around       mid-oesophagus, forming two discrete trunks below that
*** Beware left RLN above       aortic arch
** '''Phreno-oesophageal      ligament'''
*** Attaches the oesophagus       anteriorly to the peritoneum, and endo-abdominal fascia
*** Formed as a condensation of       the '''endo-abdominal fascia''' from the under-surface of the diaphragm. The       endo-abdominal fascia splits into two layers - filmy outer layer,       continuing downwards to GOJ; and a stronger superior layer which passes       upwards through the hiatus to blend with areolar tissue surrounding the       oesophagus.
*** Seen macroscopically as the       layer of tissue which binds the oesophagus to the edges of the       oesophageal hiatus, seen as a white line similar in appearance to the       white line of Toldt elsewhere.

=== '''Path:''' ===

** Begins at the lower border      of the cricoid cartilage (C6), at the base of the pharynx, in the midline
*** Posteriorly related to       pre-vertebral fascia, then vertebral bodies and longus colli muscles
** It curves slightly to the      left as it passes down through the thoracic inlet and through the      superior mediastinum
** Back to midline at T5, then      deviates to right, away from aortic arch
*** Note thoracic duct directly       posterior to oesophagus at this level - high risk for injury
** At T7 passes to left again,      under the left main bronchus, and curves forward to pass in front of the      thoracic aorta
*** Pericardium and left atrium       in front
*** Anterolateral part of       thoracic vertebrae to the right
** Through the diaphragm at the      oesophageal hiatus (T10)
*** Separated from aorta by       left pillar of oesophageal hiatus
** Into the cardia of the      stomach at T11
** 3cm of oesophagus in abdomen      while supine


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=== '''Segments:''' ===

** Pharyngeal
** Cervical - from      cricopharyngeus to the thoracic inlet
** Thoracic - from thoracic      inlet to oesophageal hiatus in the diaphragm
** Abdominal - from diaphragm      to stomach

=== '''Description''' ===

** 25cm long, extending C6 to      T11
** Normally 2.5cm in diameter
** Anchored superiorly to      cricoid cartilage
** Tethered along length e.g.      to left and right pleura
** '''Upper      oesophageal sphincter''' - 15-17cm from teeth
*** Formed from the inferior       pharyngeal constrictor muscle, which acts as the bridge between the       pharyngeal and oesophageal musculature
*** Inferior pharyngeal       constrictor is formed by thyropharyngeus and cricopharyngeus muscles,       which both insert into the median pharyngeal raphe
**** Thyropharyngeus (oblique        fibres) originates from the thyroid cartilage, just adjacent to        cricothyroid
**** Cricopharyngeus        (transverse fibres) originates from the cricoid cartilage
*** Nerve supply from       pharyngeal plexus
*** The high-pressure zone of       cricopharyngeus forms a true anatomic sphincter (mean pressure 60mmHg) -       thus the lower part of inferior pharyngeal constrictor forms the upper       oesophageal sphincter
*** Killian triangle is a site       of potential weakness, between the fibres of the two pharyngeal       constrictor muscles. This is the site of Zenker diverticulae.
*** V-shaped area of Laimer       forms at the apex of the longitudinal oesophageal muscles extending up       towards the posterior surface of the thyroid cartilage
*** If incising the inferior       pharyngeal constrictor, make the incision as posterior as possible to       avoid damaging or constricting the arytenoids and other muscles of the       laryngeal inlet
***

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=== '''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)
***

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=== '''Anatomical     areas of narrowing:''' ===

** UOS - 14mm diameter - 15cm      from incisors
** Bronchoaortic constriction      (T4) - 15-17mm diameter - 25cm from incisors
** Diaphragmatic constriction      (T10) - 16-19mm diameter - 40cm from incisors
**