Esophagus Anatomy and Embryology

• The esophagus is covered in this presentation.

Embryology

• Esophagus development starts during week 3 of gestation.
• It is derived from the endoderm lined yolk sac cavity in the primitive gut.
• A ventral diverticulum, which develops during week 3, forms the tracheobronchial tree.
• By week 12, the mucosa is completely differentiated.
• The muscular layer begins developing from the mesoderm in week 6 and is fully formed by week 12.
• A functional swallow is first observed around week 14 and becomes well established by 4 months of gestation.

Gross Anatomy

• The esophagus is a muscular tube that is about 25 cm long.
• It extends from the lower border of the cricoid to the stomach, spanning from C6 to T11.
• There are two curves in the coronal plane and three constrictions present.

Esophagus Parts

• The esophagus is studied in three main parts: cervical, thoracic, and abdominal.
• Anatomical features, pathologies, surgical approaches, and management options are specific to each of these parts.

Cervical Part Relations

• Anteriorly, the cervical esophagus relates to the trachea.
• Posteriorly, it relates to the prevertebral muscles and fascia covering the 6th to 8th cervical vertebrae.
• Laterally, it relates to the carotid sheath and the lower poles of the thyroid gland.
• The thoracic duct is located on the left side at the C6 level.

Thoracic Part Relations

• The presentation contains a diagram indicating the relations of the thoracic part of the esophagus.

Abdominal Part Relations

• This esophageal segment is of variable length.
• Anteriorly lies the esophageal groove on the posterior surface of the liver.
• It is related to the greater sac anteriorly and on the left.
• The lesser sac peritoneum is found on the right side.
• It is closely related to the vagus nerves.

Gastro Esophageal Junction

• Externally, the gastroesophageal junction is marked by the Collar of Helvetius and the gastroesophageal fat pad.
• Endoscopically, it is identified by the Z line, a transition from the smooth lining of the esophagus to the rugal folds in the stomach.

Blood Supply

• The cervical part receives its blood supply from the inferior thyroid artery.
• The thoracic part is supplied by bronchial and esophageal branches of the descending aorta.
• The abdominal part receives blood from ascending branches of the left phrenic and left gastric arteries.

Venous Drainage

• Venous drainage begins with the submucosal plexus, leading to the periesophageal venous plexus, and then to esophageal veins.
• Cervical portion drains via the inferior thyroid vein.
• The thoracic part drains via the Azygos vein, Hemiazygos veins, Intercostal veins, and Bronchial veins.
• The abdominal part drains via the left gastric vein.
• There is a Porto systemic anastomosis involved.

Nerve Supply

• The enteric nervous system includes Auerbach's plexus in the intermuscular plane and Meissner's plexus in the submucosal plane.
• Extrinsic nervous system includes:
  • Parasympathetic supply from the vagus nerve via recurrent laryngeal nerves.
  • Sympathetic supply from thoracic spinal cord segments.

Lymphatic Drainage

• Lymphatic plexuses in the submucosa and muscularis drain into regional lymph nodes.
• Lymph from the cervical esophagus drains into the paratracheal, deep cervical, and internal jugular nodes.
• Lymph from the thoracic part drains into the mediastinal nodes, paratracheal, subcarinal, retro cardiac, infracardiac lymph nodes, and the thoracic duct.

Histology

• There are four layers of the esophagus:
  • Mucosa: stratified squamous epithelium
  • Submucosa: containing brenners glands
  • Muscularis propria: inner circular and outer longitudinal muscle fibers
  • Adventitial layer
• There is no serosal layer on the esophagus.