Oesophagus - Anatomy & Physiology

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Introduction

The oesophagus (or gullet) is a muscular tube which transports food from the pharynx to the stomach. A bolus of food is passed down the oesophagus by peristalsis.

The oesophagus is divided into cevical, thoracic and abdominal sections.

Structure and Function

Oesophagus Anatomy - Copyright RVC 2008
  • Begins dorsal to cricoid cartilage of larynx
  • Follows trachea down neck, first on the left and then medially once in thorax in the mediastinum
  • Passes over heart then through the oesophageal hiatus of the diaphragm
  • Passes over the dorsal border of the liver then joins the stomach at the cardia
  • The cervical section is accompanied by the common carotid artery, the vagosympathetic trunk and the recurrent laryngeal nerves
  • The thoracic section is accompanied by the right and left vagus nerves (CN X)
  • Different proportions of striated muscle across the species
  -Dog and ruminant = 100%
  -Cat              = 80% (rostral)
  -Horse            = 65% (rostral)
  -Pig              = 33% (rostral)


Histology

Oesophagus Histology (Rat) - Copyright RVC 2008
  • Stratified squamous epithelium
  • Mucosal folds for distension
  • Degree of keratinisation depend on diet
  • Lamina propria contains collagen and elastic fibres sparsely distributed
  • Lamina muscularis is smooth muscle
  • No glands in mucosa
  • Mucous glands (tubulo-acinar) present in submucosa
  • Inner circular layer of tunica muscularis thickens near gastric junction forming a sphincter
Oesophagus Structure Diagram - Copyright NOTTINGHAM 2008

Innervation

  • Sympathetic nerves
  • Parasympathetic from the vagus nerve (CN X) and recurrent laryngeal nerves
  • Myenteric plexus extends the length of the oesophagus


Species Differences

  • Mucous glands present in horse, cats and ruminants only at pharyngeal-oesophageal junction
  • Thick and strong sphincter of tunica muscularis in dogs and pigs
  • Ruminants, horse and pig have stratified squamous epithelium continuing from oesophagus into stomach. carnivores have an abrupt transition to columnar epithelium.

Canine

  • Canid has no keratinisation
  • Lamina muscularis present caudally in dogs (spirally aranged)
  • Lamina muscularis absent cranially in dogs
  • Mucous glands throughout in dog but more abundant caudally

Equine

  • Horse has some keratinisation

Ruminant

  • Ruminant has a lot of keratinisation

Porcine

  • Lamina muscularis present caudally in pigs (very thick)
  • Lamina muscularis absent cranially in pigs
  • Pig has some keratinisation
  • Mucous glands abundant cranially but absent caudally in pig

Avian

  • Ducks have an oesophangeal tonsil present in the caudal segment of oesophagus

Links

Oesophagus Pathology

Megoesophagus