Oesophagus and its Disorders Flashcards
Describe the anatomy of the oesophagus.
- fibromuscular tube of striated squamous epithelium
- posterior to the trachea/beneath cricoid cartilage
- begins at the end of the laryngopharynx and joins the stomach a few centimetres from the diaphragm (at the cardiac orifice)
What promotes the transport of ingested food into the stomach?
- Relaxation of the sphincters (UOS and LOS).
- Contraction and relaxation of the oesophagus
Describe the two sphincters of the oesophagus.
- UOS (upper oesophageal sphincter)
- LOS (lower oesophageal sphincter)
Describe the UOS.
- Striated muscle
- Musculo-cartilaginous structure
- Constricted to avoid air entering the oesophagus.
Describe the LOS.
- Smooth muscle
- High-pressure area.
- Has extrinsic and intrinsic components
What are the intrinsic components of the LOS?
Oesophageal muscles, under neurohormonal influence
What are the extrinsic components of the LOS?
Diaphragm muscle
Describe the intrinsic components of the LOS. PART 1
- Thick, circular smooth muscle layers.
- Clasp-like, semicircular smooth muscle fibres (on the right-hand side) giving myogenic activity but less ACh-responsive
Describe the intrinsic components of the LOS. PART 2
Sling-like, oblique gastric (angle of His) muscle fibres on the left-hand side
- works with clasp-like smooth muscle fibres to help prevent regurgitation - responsive to cholinergic innervation
Why is reflux common in infants?
Poorly developed Angle of His
Describe the extrinsic components of the LOS. PART 1
- Crural diaphragm encircles the LOS
- Diaphragm forms channel through which the oesophagus enters the abdomen.
Describe the extrinsic components of the LOS. PART 2
- Fibres of the crural portion of the diaphragm posses a ‘pinchcock-like’ action
- Stops reflux of acidic chyme into the oesophagus
Describe the neural innervation of the oesophageal sphincters.
- acetylcholine: contraction of intrinsic sphincters
- NO, VIP: relax the intrinsic sphincters
Describe the neural innervation of the upper part of the oesophagus.
- Made up of striated muscle
- Supplied by somatic motor neurons of the vagus nerve without interruptions (i.e vagus and splanchnic nerve)
Describe the neural innervation of the lower part of the oesophagus.
- Made up of smooth muscle
- Innervated by visceral motor neurons of the vagus nerve with interruptions
- Synapse with postganglionic neurons; cell bodies in the oesophagus and splanchnic plexus
Describe upper oesophageal motor innervation.
- Innervated directly by the somatic efferent cholinergic fibres of the vagus nerve
- Originate from the nucleus ambiguus (releasing stimulatory ACh).
Describe distal oesophageal motor innervation.
- Preganglionic vagus nerve fibres from the dorsal motor nucleus.
- ACh affects post-ganglionic neurons in the myenteric plexus
What are the two types of post-ganglionic neurons in the myenteric plexus affected by ACh?
Excitatory cholinergic neurons and inhibitory nitrinergic neurons
List some functions of the oesophagus.
- swallowing (deglutition)
- conveys food and fluids from the pharynx to the stomach
Describe the coordination of swallowing. PART 1
Triggered by afferent impulses in the trigeminal, glossopharyngeal and vagus nerves.
Describe the coordination of swallowing. PART 2
- Efferent impulses pass to the pharyngeal musculature and the tongue
- Trigeminal, facial and vagus nerves supply the tongue muscles
Describe the coordination of swallowing. PART 3
- Integration of these impulses occurs in the NTS, the nucleus ambiguus (NA) and the dorsal vagal nucleus (DVN).
How is swallowing initiated?
- VOLUNTARY actions, where material collected on tongue and push it backwards into the pharynx
- waves of INVOLUNTARY contractions push the material into the oesophagus
What supplementary events occur during swallowing? PART 1
- inhibition of respiration, so the nasopharynx is closed off
- closure of the glottis (around the vocal cords) by the epiglottis
What supplementary events occur during swallowing? PART 2
- ring of peristaltic waves behind the material move it towards the stomach
- second wave of peristalsis
Why is secondary peristalsis necessary?
A lot of food material does not reach the stomach after the first peristaltic wave.
What causes secondary peristalsis?
- Stimulation of receptors upon distention of the lumen of the oesophagus by the food
- Causes repeated waves of peristalsis
What prevents the reflux of gastric contents?
- LOS (closes after material passes)
- ‘pinchcock’ effect of the diaphragmatic sphincter on the lower oesophagus
- plug-like action of the mucosal folds in the cardia
Expand on the pathophysiology of achalasia. PART 1
- impaired LOS relaxation
- can be accompanied by impaired peristalsis (sphincter spasms)
- foods and liquids fail to reach the stomach (delayed emptying of LOS)
Expand on the pathophysiology of achalasia. PART 2
- dilation of the oesophageal body with distal narrowing
- long periods of sporadic dysphagia (difficulty swallowing)
- regurgitation of food
List some causes of achalasia. PART 1
- disorders of peristalsis in oesophagus
- damage to the innervation of the oesophagus
List some causes of achalasia. PART 2
- degenerative lesions of the vagus nerve, and loss of the myenteric plexus ganglionic cells in the oesophagus
List some symptoms of achalasia.
- dysphagia
- vomiting
- heartburn
What are two tests used in the diagnosis of achalasia?
- BARIUM RADIOGRAPHY: allows for the evaluation of the mouth, pharynx and oesophagus
- OESOPHAGEAL MANOMETRY: checks to see if the oesophagus is contracting/relaxing properly
What does low LOS pressure suggest?
GORD
What do high LOS pressures suggest?
<26 mmHg = normal
>100 mmHg = achalasia
What would normal results of oesophageal manometry show?
- pressure of the muscle contractions that move food down the oesophagus is normal
- muscle contractions follow a normal pattern down the oesophagus
What would abnormal results of oesophageal manometry show?
- presence of muscle spasms in the oesophageal body
- presence of weak contractions along the length of the oesophagus
Describe reflux in normal individuals.
- Brief, and relatively infrequent.
- Often occurs after meals in normal individuals (due to transient spontaneous LOS relaxation).
- Usually stimulates salivation.
What is the effect of saliva?
Natural antacid - dilutes and neutralises the refluxed gastric contents.
What is GORD?
Gastro-Oesophageal Reflux Disease.
- Reflux is more frequent and troublesome.
- Low rate of salivation.
What is the effect of a low rate of saliva in GORD?
- Lack of ability to swallow own saliva
- Prolongation of contact of the refluxed material with the oesophagus.
- Results in oesophageal irritation and damage.
List some causes of reflux in those with GORD.
- transient spontaneous LOS relaxation (TSR)
- resting LOS tone is too weak to resist the pressure within the stomach
- sudden relaxation of the LOS that isn’t induced by swallowing
What are some factors that could contribute to the severity of GORD?
- weak or uncoordinated oesophageal contractions
- length of time the oesophagus is exposed to gastric acid
- amount of pressure placed on the anti-reflux barrier
What are some factors associated with GORD?
- pregnancy/obesity
- fat, chocolate, coffee or alcohol ingestion
- cigarettes
- drugs (eg. anticholinergic agents, calcium channel clockers and nitrate drugs)
What are some symptoms of GORD?
- heartburn and acid regurgitation/decreased acid clearance
- waking up at night (due to larynx irritation)
- dysphagia (difficulty swallowing)
How would you investigate GORD?
- low dose proton pump inhibitor (PPI)
- upper GI endoscopy
- manometry
- 24-hour ambulatory pH monitoring
How does pregnancy affect GORD? PART 1
- Foetus increases the pressure on the abdominal contents.
- Pushes the terminal segments of the oesophagus into the thoracic cavity.
How does pregnancy affect GORD? PART 2
- Last trimester of pregnancy is associated with increased abdominal pressure
- Forces gastric contents into the oesophagus.
- Heartburn subsides in the last months as the uterus descends into the pelvis.
What are some potential long-term effects of GORD?
- oesophagitis (inflammation)
- Barrett’s Syndrome - this may predispose someone to oesophageal adenocarcinoma
- oesophageal ulcer
Describe the management and drug treatment of GORD. PART 1
- Lifestyle changes e.g losing weight, avoiding food that increases gastric acidity, that slow gastric emptying, avoiding drugs and smoking, etc.
Describe the management and drug treatment of GORD. PART 2
- Anti-reflux surgery (fundoplication, where you wrap the fundus around the LOS).
- Taking antacids, H2-receptor antagonists and proton pump inhibitors.
Describe a possible problem with the use of antacids in the treatment of GORD.
- Neutralise gastric acid, increasing the pH of the gastric lumen.
- Inhibit peptic activity and stop acid secretion.
- Contain magnesium salts cause diarrhoea while aluminium salts cause constipation.
What happens if GORD becomes more serious? PART 1
- Oesophagus naturally has squamous mucosa
- Acid reflux could lead to the desquamation of oesophageal cells.
- Increased cell loss causes basal cell hyperplasia.
What happens if GORD becomes more serious? PART 2
- Excessive desquamation causes ulceration.
- Ulcers may haemorrhage, perforate or heal by fibrosis with strictures.
- Leads to Barrett’s oesophagus and oesophageal cancer.
What is the angle between the cardiac orifice and the fundus called?
→ Angle of His
What is the LOS for?
→ Remains open as long as swallowing is occurring
→ Close to prevent reflux of the stomach contents into the oesophagus
What is swallowing difficulty caused by?
→ Inability of the UOS to open
→ Discoordination of the timing between opening of UOS and pharyngeal push of the ingested bolus
What do circular muscles act as and why?
→ Act as valves to control the movement of the food mass aborally
→ Prevents reflux by forming an opening when relaxed and closing completely when contracted
What is a diffuse oesophageal spasm?
→ Chest pain coming from the oesophagus
What is oesophageal spasm?
→ Abnormal oesophageal contractions
→ Food is not effectively reaching the stomach
What is reflux?
→ retrograde movement of gastric content into the oesophagus due to the relaxation of the LOS
Why do you get heartburn in the absence of pregnancy?
→May occur in some individuals upon eating large meals
→Less efficient LOS
What happens to gastric contents during heartburn?
→episodically refluxed into the oesophagus
What can happen as a result of heartburn?
→Ulcer
→ scarring
→obstruction or perforation of the lower oesophagus
When is manometry ordered?
→Heartburn or nausea after eating GORD
→Problems swallowing
What do Metoclopramide/domperidone do?
→enhance peristalsis and help gastric clearance
What do you combine with alginates for reflux?
→ Combine alginates (e.g. gaviscon) with antacids for oesophageal reflux
What do alginic acid and saliva form?
→Alginic acid + saliva form a ‘raft’ which floats on content of gastric lumen and protects the oesophageal mucosa from reflux
What is essential to stop the ulcer returning?
Removal of H Pylori
