Anatomy of the Oesophagus
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🦴 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.
