Oesophageal anatomy

Oesophageal embryology

Overview

• Starting point: Lower border of cricoid cartilage (level of C6)
• Passes through diaphragm at level of T10
• Ends in abdomen at the cardiac orifice of stomach at level of T11
• Length: 25cm
• Terminates at about 40cm from the incisors in the average adult
• NB: Air does not enter the oesophagus on inspiration because tonic contraction of the Cricopharyngeus muscle is maintained through its innervation by the Vagus nerve

Oesophageal Wall

• Upper part
  • Striated muscle
  • Striated muscle and upper oesophageal sphincter derived from mesenchyme of branchial arches 4,5,6
    • Explains upper oesophageal sphincter innervation
      • Vagus – nerve of branchial arch 5
      • Recurrent Laryngeal – nerve of branchial arch 6
• Middle part
  • Mixed
• Lower part
  • Smooth muscle
  • From splanchnic mesoderm
  • Lower oesophageal sphincter innervated both by
    • Parasympathetic – Vagus N
    • Sympathetic – Mostly splanchnic N

Congenital Anomalies

• Rare – 1/3000-5000
• Oesophageal atresia
  • Failure of recannalisation
• Tracheo-oesophageal fistulae
  • Failure of lateral invaginations
• Stenosis, Web, Muscular Hypertrophy
  • Abnormal recannalisation
• Duplication Cyst

Layers of the Oesophagus

• Mucosa
  • Epithelium
  • Lamina propria
  • Muscularis mucosa
• Submucosa
  • Contains lymphatics
• Muscularis externa / propria
  • (Does not have Inner oblique like the stomach), inner circular and outer longitudinal
  • Myenteric (Auerbach’s) plexus
• Serosa

Notes

• Thicker longitudinal layer forms continuous outer coat EXCEPT at the top, where 2 tendinous bands ascend within the lower border of the Inferior Pharyngeal Constrictor and get attached to the midline ridge on the back of the lamina of the Cricoid Cartilage
• Circular muscle reaches higher than longitudinal to become continuous with Cricopharyngeus muscle
• No serous covering (except for the short intra-abdominal segment)
• Thick muscularis mucosae
• Surface epithelium: Non-keratinised stratified squamous
  • Replaced by simple columnar epithelium at GOJ
  • Abnormal to have squamocolumnar junction ≥ 3cm above GOJ
• Submucosa has mucous glands – sparse – found mostly in upper and lower ends of oesophagus

Gross Anatomy

• Traverses – neck, thorax, abdomen
• 25cm long, 38-40cm from incisors
  • Cervical 5cm
  • Thoracic 20cm
  • Abdominal 2cm
• Muscular tube, no serosa except abdominal portion
• Narrowest tube in alimentary tract except appendix
• Commences in midline
  • Below cricophyaryngeus (level of C6)
• Ends at cardia of stomach (level of T11)

Sphincters

• Upper oesophageal sphincter
  • Cricopharyngeus, 4-5cm long
  • Resting pressure 60-100mmHg
• Lower oesophageal sphincter
  • Lower 4cm of inner circular muscle
  • Not actually any thicker here (physiologic sphincter)
  • Resting pressure 10-20mmHg
  • Works by
    1. Oesophagus entering stomach at acute angle
    2. Positive intra-abdominal pressure compresses the walls
    3. Mucosal folds occlude lumen
    4. Right crus has “pinch-cock” effect

Gastro-oesophageal Junction

• 4 anatomic points that can identify this
• On gastroscopy
  • The squamo-columnar junction if no Barrett’s
  • The transition form smooth oesophagus to the rugal folds of stomach
  • End of the palisading vessels
• On external view
  • Collar of Helvetius
    • Where circular fibres of oesophagus join oblique fibres of stomach
  • Gastro-oesophageal fat pad

Surface markings

• Begins midline
• Inclines left at root of the neck
• At level of T5, returns to midline
• At T7, deviates left again, curves forward over aorta
• Pieces diaphragm at T10
  • 2.5cm to left of midline
  • Level of 7th costal cartilage
• Constrictions (measured from incisors)

1. Cricopharyngeal sphincter – 15cm from incisor teeth (narrowest part of oesophagus)
2. Aortic arch – 22cm from incisors
3. Left main bronchus – 27cm from incisors
4. Oesophageal hiatus in diaphragm – 38cm from incisors NB: Left atrium is anterior to oesophagus below the Left main bronchus – it is only indents the oesophagus when enlarged

Relationships

Cervical Oesophagus

Course

• Commences in continuity with the pharynx at level of lower border of Cricoid Cartilage (C6)
• Anterior to pre-vertebral fascia
• Posterior to trachea
• Enters thoracic cavity via thoracic inlet Relations
• Overlapped on either side by lower poles of thyroid gland
• Thoracic duct runs upwards behind the lower part of its left border
• Recurrent laryngeal nerve are on each side in the groove between trachea and oesophagus

Thoracic Oesophagus

Course

• Commences in midline in front of Pre-Vertebral Fascia
• Enters the Thoracic Inlet in the midline
• Passes downwards through Superior Mediastinum inclining to the left
• Returns to midline at level of T5
• Deviates to the left at T7
• Curves forwards to pass anterior to the Descending Thoracic Aorta
• Pierces diaphragm 2.5cm to the left of midline at level of 7th Costal Cartilage
  • Fibres from right crus of diaphragm sweep around oesophageal opening in a sling-like loop
• NB: Oesophagus is directly in front of the vertebral bodies at its origin at C6
  • Stays in contact with the vertebral bodies throughout the superior mediastinum (which extends to the lower border of T4 (level of manubriosternal joint and tracheal bifurcation) Relations
• Superior Mediastinum
  • Crossed by the Aortic Arch on its left side and Azygous Vein on its right side
  • Directly posterior to trachea throughout its length
• Posterior Mediastinum
  • Just below the bifurcation of trachea, it is crossed anteriorly by the Left Main Bronchus and Right Pulmonary Artery
  • Below that, the pericardium (separating it from the Left Atrium) and the posterior sloping fibres of the diaphragm are anterior to the oesophagus
  • Thoracic duct - Posterior to the oesophagus - At first, on its right and then ascends directly behind it and lying to its left in the superior mediastinum
• More Posterior Plane
  • Hemiazygos, Accessory Hemiazygos and Right Posterior (Aortic) Intercostal Arteries cross midline
  • Mediastinal pleura touches oesophagus on both sides
  • Pocket of right pleura behind oesophagus and in front of the Azygos Vein and vertebral column
  • NB: The oesophagus is NOT closely related to the Left Phrenic Nerve or the Right Sympathetic Trunk

Abdominal Oesophagus

• 1-2cm in length Course
• Turns forwards and to the left immediately below the diaphragmatic opening
• Grooves the posterior surface of the left lobe of the liver
• Enters stomach at cardiac orifice
  • Right margin continuous with lesser curvature
  • Left margin makes an acute angle with the gastric fundus – a.k.a. the Cardiac Notch Relations
• Anterior and posterior vagal trunks related to their respective oesophageal surfaces
• Peritoneum on front and left side
• Peritoneum passes from the oesophagus on the right to the diaphragm as the uppermost part of the Lesser Omentum and on the left forms the uppermost part of the Greater Omentum
• Inferior Phrenic Artery – posterior to Oesophagus

Abdominal Relationships

• 1-4cm in length
• Right and anterior is right crus and liver
• Left and anterior is left crus and peritoneum
• Right edge contiguous with lesser curve
• Left terminates at Angle of His at cardiac notch
• Vagii anterior (from left) and posterior (from right)
• Descending aorta posteriorly

Blood supply

Arterial Supply

• Upper Oesophagus:
  • Supplied by Inferior Thyroid Arteries
• Middle Oesophagus:
  • Oesophageal branches from Aorta
  • Bronchial arteries
• Lower Oesophagus:
  • Oesophageal branches of Left Gastric Artery

Venous Drainage

• Upper oesophagus:
  • Brachiocephalic veins
• Middle oesophagus:
  • Azygos system of veins
• Lower oesophagus:
  • Oesophageal tributaries of Left Gastric Vein which empties into Portal Vein
    • Thus, in lower oesophagus exist an anastomosis between portal and systemic venous systems
    • Anastomosis lies at the level of Central Tendon (T8) well above the oesophageal hiatus
    • In portal obstruction, these become oesophageal varices

Lymphatic Drainage

• From cervical oesophagus: Drain to Deep Cervical Nodes
• From thoracic oesophagus: Drain to Tracheobronchial and Posterior Mediastinal Nodes
• From abdominal oesophagus: Drain to Left Gastric and Coeliac Nodes
• Within oesophageal walls – lymphatic channels enable lymph to pass for long distances – thus, drainage from any given area does not strictly follow the above pattern

Nerve Supply

• Upper Oesophagus:
  • Recurrent Laryngeal Nerves
  • Sympathetic fibres from cell bodies in the Middle Cervical Ganglia running in on the Inferior Thyroid Arteries
• Middle and Lower Oesophagus:
  • Supplied by Thoracic Sympathetic Trunks and Greater Splanchnic Nerves, and Parasympathetic fibres from Vagus nerves – forms plexus on surface of oesophagus
  • Over last few centimetres of Thoracic Oesophagus – Anterior and Posterior Vagal Trunks form from this plexus
    • Anterior Vagal Trunk – predominantly Left Vagal fibres
    • Posterior Vagal Trunk – predominantly Right Vagal fibres BUT, both trunks have fibres from both Vagi
  • Motor supply: Vagus nerves, from cell bodies in the…
    • Nucleus Ambiguous for the upper striated muscle
    • Dorsal Motor Nucleus with relay in the plexuses in the wall for the lower visceral muscle part
      • Left Vagus – supplies anterior surface
      • Right Vagus – supplies posterior surface
• Glands: secretomotor fibres from Vagus and the Vasomotor sympathetic supply

Surgical Approach

• Cervical oesophagus: Left side of neck by opening up interval between Trachea and Carotid Sheath
• Thoracic oesophagus: Right side in front of the vertebral column after transecting Azygos arch
  • Posterior intercostal vessels and Thoracic Duct at risk when mobilizing oesophagus posteriorly
• Lower oesophagus: More easily approached from left side above the diaphragm in the interval between the pericardium in front and the Aorta behind
• GOJ: Approached through abdomen
• Maximum access to lower oesophagus and stomach is obtained via a thoracoabdominal incision with division of the diaphragm