The Oesophagus & Its Disorders

Question 1

Describe the anatomy of the Oesophagus

Answer 1

• 25cm Fibromuscular tube lined with STRATIFIED SQUAMOUS epithelium
o Skeletal muscles around the upper 1/3 to form the Upper Oesophageal Sphincter (UOS) - constricted to prevent air entering oesophagus
o Smooth muscles around the lower 2/3 to form the Lower Oesophageal Sphincter (LOS) - area of high pressure
• Posterior to Trachea - begins at the Laryngopharynx and ends at diaphragm
• Transports food from mouth to stomach, and secretes mucous

Question 2

Describe the components of the Lower Oesophageal Sphincter

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Answer 2

• Thick smooth muscles - clasp-like, semi-circular muscle fibres
• Oblique, sling-like muscle fibres on the left - helps prevent regurgitation
• Crural diaphragm encircles the LOS - forms oesophageal hiatus

Question 3

Describe the innervation of the oesophageal sphincters

Answer 3

• Cholinergic and NANC innervation controlling the tone of the LOS
• Contraction uses ACh, and Relaxation uses VIP/NO

Question 4

What innervates the upper and lower parts of the oesophagus?

Answer 4

Upper part:
Striated muscle innervated by Somatic Motor neurons from Vagus and Splanchnic nerves - no interruptions

Lower part:
Smooth muscle innervated by Visceral Motor neurons from Vagus nerve - has interruptions
Synapses with postganglionic neurons in oesophageal and splanchnic plexus

Question 5

How is swallowing initiated?

Describe the voluntary and involuntary mechanisms of the oesophagus

Answer 5

• • Triggered by afferent impulses (Trigeminal, Glossopharyngeal, Vagus nerves)
  • Efferent impulses pass to the pharyngeal muscles and tongue (Trigeminal, Facial, Hypoglossal)
  • Integration of impulses from the NTS, NA, Dorsal Vagal Nucleus
• Voluntary - Collect material on tongue and push it backwards into pharynx
  Involuntary - Waves of contractions push material into oesophagus

Question 6

What are the reflex responses that occur during swallowing?

Answer 6

• Inhibition of breathing as nasopharynx is closed off, and the epiglottis closes the glottis (top of trachea)

• Primary Peristalsis - Peristaltic waves behind the bolus (material) to move it towards the stomach
o Food hasn’t entered stomach yet

• Secondary Peristalsis - Second wave of Peristalsis moves any remaining material along
o Distension of lumen stimulates receptors, causing secondary peristalsis

• UOS + LOS opens, and then closes once food passes
o Glottis and nasopharynx reopen, and breathing resumes

Question 7

What happens to prevent the reflux of gastric contents?

Answer 7

1. LOS - closes after material passes
2. “Pinchcock” effect of the diaphragmatic sphincter on the lower oesophagus
3. Plug-like action of the mucosal folds in the cardia - occludes the lumen of the gastro-oesophageal junction
   o Abdominal pressure acts on the intra-abdominal oesophagus
   o Valve-like effect of oblique entry of oesophagus into stomach - in adults

Question 8

What is Achalasia?

What occurs during it?

What are the causes?

How is it diagnosed and treated?

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Answer 8

• Disorder of oesophageal peristalsis
• • Impaired LOS relaxation, with/without impaired peristalsis
  • Material fails to reach stomach, which can result in dilation of the lower oesophagus = Dysphagia and regurgitation/vomiting
  • Weight loss and Heartburn are also common symptoms
• Damage to oesophagus innervation - lesions of vagus nerve or loss of oesophagus ganglionic cells
• • Barium Radiography - distension of oesophagus with “beak” deformity at lower end
  • Oesophageal Manometry - no/weak peristalsis

Question 9

What is GORD?

What does it lead to?

What are the causes?

What are the treatment and managements options for GORD?

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Answer 9

• • Retrograde movement of gastric contents into oesophagus due to relaxation of LOS - Causes heart burn
  • Often briefly occurs after large meals, and it usually stimulates saliva
• GORD causes de-squamation of the oesophageal lining - triggers basal cell hyperplasia:
  • Excessive desquamation leads to Ulcerations, which may perforate, haemorrhage, or heal by fibrosis
  • Barrett’s Oesophagus - change in mucosal lining
  • Squamous cell carcinoma
• • Spontaneous LOS relaxation
  • Resting LOS pressure is too weak to resist the pressure within the stomach
  • Sudden LOS relaxation - not induced by swallowing
  • Poor Oesophageal peristalsis can cause poor clearance of regurgitated acids - oesophageal damage
  • Impaired gastric emptying
  • Hiatus hernia
• • Lifestyle changes
  • Dietary changes
  • Fundoplication to prevent reflux - reduce LOS distensibility
  • Drugs: Antacids, H2 antagonists, PPIs