Oesophagus and its Disorders Pt. 1

• What is the oesophagus?

  A muscular tube that connects the pharynx to the stomach, allowing the passage of food and liquids.
• What is the approximate length of the oesophagus?

  25cm long in adults
• Where does the oesophagus start and end

  • Begins at the C6 vertebra (continuous with the pharynx)
  • Passes through the diaphragm at T10
  • Ends at the T11 vertebra (joins the stomach at the gastro-oesophageal junction)
• What are the three anatomical constrictions of the oesophagus?

  1. Cervical constriction – at the cricopharyngeal sphincter (~C6).
  2. Thoracic constriction – at the crossing of the aortic arch and left main bronchus (~T4/T5).
  3. Diaphragmatic constriction – at the oesophageal hiatus (~T10).
• What are the four layers of the oesophageal wall?

  1. Mucosa – Non-keratinised stratified squamous epithelium.
  2. Submucosa – Contains mucous glands for lubrication.
  3. Muscularis externa – Divided into upper (skeletal), middle (mixed), and lower (smooth) muscle layers.
  4. Adventitia – Connective tissue anchoring the oesophagus to surrounding structures.
• What type of muscle is found in the oesophagus?

  • Upper third → Striated (skeletal) muscle (voluntary).
  • Middle third → Mixed striated and smooth muscle.
  • Lower third → Smooth muscle (involuntary).
• Is the lower oesophageal sphincter anatomical or physiological?

  It is a physiological sphincter (not a distinct muscle but a high-pressure zone).
•  How is the lower oesophageal sphincter regulated?

  It is controlled by autonomic innervation, hormones (gastrin, motilin), and intra-abdominal pressure.
• What are the main sources of autonomic innervation to the oesophagus?

  The oesophagus receives autonomic innervation from the vagus nerve (parasympathetic) and the sympathetic trunk.
•  What is the role of parasympathetic innervation in the oesophagus?

  • Stimulates peristalsis and relaxes the lower oesophageal sphincter.
  • Mediated by the vagus nerve (CN X) via the oesophageal plexus.
• What is the role of sympathetic innervation in the oesophagus?

  • Inhibits peristalsis and constricts blood vessels.
  • Arises from the sympathetic trunk (T1-T5) via the greater splanchnic nerves.
• What is the upper oesophageal sphincter (UOS)?

  A high-pressure zone at the junction of the pharynx and oesophagus, composed mainly of the cricopharyngeal muscle, which prevents air entry into the oesophagus and reflux of gastric contents.
• What type of muscle makes up the upper oesophageal sphincter?

  Composed of striated skeletal muscle, primarily the cricopharyngeal, thyropharyngeal, and upper oesophageal muscles, allowing voluntary and reflexive control.
• What neural mechanisms control the opening of the UOS?

  Controlled by the swallowing reflex, regulated by the brainstem swallowing centre (nucleus ambiguus and dorsal motor nucleus of the vagus) via the vagus nerve (cranial nerve X) and glossopharyngeal nerve (cranial nerve IX).
• What triggers the UOS to open during swallowing?

  • Initiation of swallowing by the oral and pharyngeal phases.
  • Relaxation of the UOS muscles due to inhibition from the swallowing centre in the medulla.
  • Upward and forward movement of the larynx pulls the UOS open mechanically.
  • Propulsion of the food bolus by tongue and pharyngeal constrictors.
• What is the sequence of events leading to UOS opening?

  • Voluntary initiation – Tongue pushes bolus to the pharynx.
  • Pharyngeal phase (involuntary)
  • Soft palate elevates to prevent nasal regurgitation.
  • Vocal cords adduct and larynx elevates and moves forward.
  • UOS relaxes due to inhibition from the swallowing center.
  • Pharyngeal constrictors contract to push the bolus through the sphincter.
  • Bolus enters the oesophageal body – UOS contracts again to prevent backflow.
• What role does laryngeal elevation play in UOS opening?

  Laryngeal elevation and forward movement reduce UOS pressure and facilitate its opening, preventing aspiration and allowing smooth bolus passage.
• How does the UOS return to a closed state after swallowing?

  After the bolus passes, the UOS regains tonic contraction due to:

  • Rebound contraction of cricopharyngeus muscle.
  • Restored excitatory input from the swallowing center.
  • Elastic recoil of the larynx to its resting position.
• What happens if the UOS fails to open properly?

  Dysfunction of the UOS leads to oropharyngeal dysphagia, characterised by difficulty swallowing, choking, and regurgitation.
• What is cricopharyngeal achalasia?

  A disorder where the UOS fails to relax properly, causing food to accumulate in the pharynx, leading to dysphagia, coughing, and aspiration.
• How does Zenker’s diverticulum relate to UOS dysfunction?

  Zenker’s diverticulum is a posterior outpouching of the pharyngeal wall due to excessive pressure from UOS dysfunction, leading to dysphagia, regurgitation, and halitosis.
• What neurological disorders affect UOS opening?

  • Stroke – Can impair swallowing reflex and UOS relaxation.
  • Parkinson’s disease – Causes delayed relaxation and poor coordination.
  • Amyotrophic lateral sclerosis (ALS) – Affects motor neurons controlling UOS function.
• What is the impact of aging on UOS function?

  Aging leads to reduced laryngeal elevation and delayed UOS relaxation, increasing the risk of aspiration and dysphagia.
• How can UOS dysfunction be diagnosed?

  • Video fluoroscopic swallow study (VFSS) – Visualises bolus movement and sphincter function.
  • Manometry – Measures UOS pressure and coordination.
• How is UOS dysfunction treated?

  • Speech and swallowing therapy – Exercises to improve laryngeal elevation.
  • Botulinum toxin injections – Reduce UOS hypertonicity.
  • Cricopharyngeal myotomy – Surgical cutting of the cricopharyngeus to aid relaxation.
• What is primary peristalsis in the oesophagus?

  A wave of muscular contraction that propels a swallowed bolus down the oesophagus.
• What triggers the primary peristalsis in the oesophagus?

  Initiated by swallowing (voluntary phase) and controlled by the swallowing centre in the brainstem (medulla)
• What is secondary peristalsis in the oesophagus?

  A reflexive peristaltic wave that clears residual food or refluxed gastric contents.
• What triggers the secondary peristalsis in the oesophagus?

  Stimulated by oesophageal distension (e.g., if food remains stuck or acid reflux occurs).
• What is the mechanism of secondary oesophagus peristalsis?

  • Does not require input from the swallowing centre in the brain.
  • Mediated by local reflexes in the enteric nervous system.
• How do primary and secondary peristalsis differ in terms of control?

  • Primary Peristalsis:
  • Initiated voluntarily via swallowing.
  • Controlled by the brainstem (central mechanism).
  • Vagus nerve plays a crucial role.
  • Secondary Peristalsis:
  • Triggered by local oesophageal distension.
  • Mediated by the enteric nervous system.
  • Can occur independently of the vagus nerve.
• What is the function of the lower oesophageal sphincter (LES)?

  • Prevents gastric reflux by maintaining tonic contraction.
  • Relaxes during swallowing to allow food to pass into the stomach.
• What neurotransmitters regulate the tone of the lower oesophageal sphincter (LES)?

  • Cholinergic control (via acetylcholine, Ach):
  • Enhances LES contraction and tone.
  • Mediated by vagus nerve stimulation of excitatory motor neurons.
  • Non-adrenergic, non-cholinergic (NANC) control:
  • Inhibits LES contraction, allowing relaxation.
  • Key neurotransmitters: Nitric oxide (NO) and vasoactive intestinal peptide (VIP).
  • Crucial for proper swallowing and bolus passage.
• How does the vagus nerve influence LES tone?

  • Excitatory pathway (cholinergic):
  • Uses Ach to stimulate contraction of LES, preventing reflux.
  • Inhibitory pathway (NANC):
  • Uses NO and VIP to relax the LES during swallowing.
• What happens if LES control is impaired?

  • Achalasia:
  • Failure of LES to relax due to defective NANC innervation.
  • Leads to difficulty swallowing and food stasis in the oesophagus.
  • Gastro-oesophageal reflux disease (GORD):
  • Weak LES tone leads to acid reflux.
  • Can cause heartburn and oesophagitis.
• What is the function of the lower oesophageal sphincter (LES)?

  Prevents reflux of gastric contents into the oesophagus by maintaining a resting tone, relaxing during swallowing to allow food passage, and contracting to prevent backflow.
• What type of muscle makes up the lower oesophageal sphincter (LES)?

  The LES is composed of smooth muscle, which is under involuntary control regulated by the autonomic nervous system and enteric nervous system.
• What controls the contraction and relaxation of the LES?

  The LES is controlled by a balance of excitatory and inhibitory neurotransmitters, mainly acetylcholine (ACh), vasoactive intestinal polypeptide (VIP), and nitric oxide (NO).
•  What is the role of acetylcholine (ACh) in LES function?

   ACh, released from excitatory vagal cholinergic neurons, increases LES tone by stimulating muscarinic receptors (M3), leading to smooth muscle contraction.
• What is the effect of vasoactive intestinal polypeptide (VIP) on the LES?

   VIP, released from inhibitory enteric neurons, causes LES relaxation by increasing intracellular cyclic adenosine monophosphate (cAMP), which leads to smooth muscle relaxation.