Makindo Medical Notes

Related Subjects: |Anatomy of the Ear |Anatomy of the Oesophagus |Anatomy of the Diaphragm |Anatomy of Large Bowel |Anatomy of Small Bowel |Anatomy of the Biliary system |Anatomy of the Eye |Anatomy of the Larynx |Anatomy of the Ear

🦴 Anatomy of the Oesophagus

The Oesophagus is a muscular tube, ~25 cm long, extending from the pharynx (C6) to the stomach. Its primary role is as a conduit for food and liquids, but it also plays an active role in swallowing and preventing reflux. 🌊

📍 General Structure

• Located posterior to the trachea and anterior to the vertebral column.
• Passes through the diaphragm at the oesophageal hiatus (T10) 🫀. (Mnemonic: “I 8 10 Eggs At 12” → IVC T8, Oesophagus T10, Aorta T12)

🏷️ Anatomical Divisions

• Cervical Oesophagus: Begins at C6 (lower border of cricoid cartilage) → thoracic inlet.
• Thoracic Oesophagus: From thoracic inlet → diaphragm, passing behind the left atrium 💓 (important for transoesophageal echo).
• Abdominal Oesophagus: Short (1–2 cm) segment, ending at gastro-oesophageal junction (Z-line).

🧩 Layers of the Oesophageal Wall

• Mucosa: Stratified squamous epithelium → protection against abrasion.
• Submucosa: Contains mucus-secreting glands for lubrication 💧.
• Muscularis Externa:
  • Inner circular → squeezes food.
  • Outer longitudinal → shortens oesophagus.
  • Upper 1/3 skeletal muscle, middle 1/3 mixed, lower 1/3 smooth muscle → key for transition from voluntary to involuntary swallowing.
• Adventitia: Outermost layer, anchors oesophagus to nearby structures.

🚪 Sphincters of the Oesophagus

• Upper Oesophageal Sphincter (UES): Prevents air entry during breathing 🌬️, opens during swallowing.
• Lower Oesophageal Sphincter (LES): Prevents reflux of gastric acid (failure → GORD/GERD 🤢).

⚙️ Physiology of the Oesophagus

🍽️ Swallowing (Deglutition)

• Complex process involving voluntary (oral) and involuntary (pharyngeal + oesophageal) phases.
• Oesophageal phase is autonomic (vagus nerve & enteric nervous system control).

🌊 Peristalsis

• Wave-like contractions push bolus toward stomach.
• Inner circular muscles contract behind bolus; outer longitudinal muscles contract ahead of it.

⚡ Oesophageal Motility

• Upper 1/3 voluntary (skeletal muscle), lower 2/3 involuntary (smooth muscle).
• LES relaxes as bolus arrives → allows passage into stomach.

🛡️ Mucosal Protection

• Mucus secretion lubricates bolus passage and protects from mechanical injury.
• LES and diaphragmatic crura prevent gastric acid reflux (failure → heartburn, Barrett’s oesophagus, strictures).

📊 Clinical Pearls

• 📌 Constriction sites (important for foreign body impaction and endoscopy):
  • Pharyngoesophageal junction (C6, cricoid cartilage)
  • Aortic arch (T4)
  • Left main bronchus (T5/6)
  • Diaphragmatic hiatus (T10)
• 📌 Clinical relevance:
  • Dysphagia can occur at physiological narrowings.
  • Transoesophageal echocardiography (TOE/TEE) uses its posterior relation to the left atrium.
  • Oesophageal cancer commonly occurs at sites of constriction.