Makindo Medical Notes

Anatomy of the Oesophagus

The Oesophagus is a muscular tube, approximately 25 cm long, that extends from the pharynx to the stomach. It functions primarily as a conduit for food and liquids.

General Structure

• The Oesophagus is located posterior to the trachea and anterior to the vertebral column.
• It passes through the diaphragm at the Oesophageal hiatus at the level of T10 vertebra.

Anatomical Divisions

• Cervical Oesophagus: Begins at the lower border of the cricoid cartilage (C6 vertebra) and extends to the thoracic inlet.
• Thoracic Oesophagus: Extends from the thoracic inlet to the diaphragm.
• Abdominal Oesophagus: A short segment (1-2 cm) located in the abdominal cavity, terminating at the gastroesophageal junction.

Layers of the Oesophageal Wall

• Mucosa: The innermost layer, lined with stratified squamous epithelium to protect against mechanical damage.
• Submucosa: Contains glands that secrete mucus to aid in the passage of food.
• Muscularis Externa: Composed of two layers:
  • Inner Circular Layer: Helps constrict the lumen to push food downward.
  • Outer Longitudinal Layer: Shortens the oesophagus during peristalsis.
  • Upper one-third is skeletal muscle, middle third is mixed skeletal and smooth muscle, and the lower third is smooth muscle.
• Adventitia: The outermost layer, providing structural support and anchoring the oesophagus to surrounding tissues.

4. Sphincters of the oesophagus

• Upper oesophageal Sphincter (UES): Prevents the entry of air during breathing and closes after food passes into the oesophagus.
• Lower oesophageal Sphincter (LES): Prevents the backflow of stomach contents (acid reflux) into the oesophagus.

Physiology of the Oesophagus

Swallowing (Deglutition)

• Swallowing is a complex process that moves food from the mouth to the stomach, involving both voluntary and involuntary muscle contractions.
• The oesophageal phase of swallowing is involuntary and is controlled by the autonomic nervous system.

Peristalsis

• Peristalsis is the coordinated, wave-like muscle contractions that propel food down the Oesophagus toward the stomach.
• The inner circular muscles contract behind the bolus of food, while the outer longitudinal muscles contract ahead of it, moving food downwards.

Oesophageal Motility

• The upper third of the Oesophagus contracts voluntarily (skeletal muscle), while the lower two-thirds function involuntarily (smooth muscle).
• The lower Oesophageal sphincter relaxes as food approaches, allowing it to pass into the stomach.

Mucosal Protection

• The Oesophageal mucosa secretes mucus to lubricate the passage of food and protect the lining from abrasion.
• The lower Oesophageal sphincter prevents the acidic contents of the stomach from damaging the Oesophageal mucosa (preventing GERD).