The Oesophagus and Its Disorders Flashcards
The oesophagus has 2 sphincters. Describe these.
Oesophagus has an upper and lower oesophageal sphincter
(UOS): striated, musculo-cartilaginous structure. Constricted to stop air entering the oesophagus
(LOS): smooth muscle; acts as a flap valve. An area of high pressure, and has intrinsic and extrinsic components
Describe and explain the intrinsic components of the LOS
Intrinsic components of LOS:
Thick circular smooth muscle layers and longitudinal muscles
Clasp-like semi-circular smooth muscle fibres on the right side. These are myogenic but less ACh-responsive
Sling-like oblique gastric (angle of His) muscle fibres on the left side. These work w the clasp semicircular smooth muscle to prevent regurgitation. ACh responsive
Describe and explain the extrinsic components of the LOS
Extrinsic components of LOS:
The crural diaphragm functions as an adjunctive external sphincter which encircles the oesophagus. It raises the pa in the LOS related to the movements of respiration.
Fibres of the crural diaphragm have myogenic “pinchcock-like” action, pressing against the sides of the oesophagus
Summarise oesophageal motor innervation
The striated upper oesophagus is innervated by somatic efferent cholinergic fibres of the vagus nerve. This vagus nerve originates from the nucleus ambiguus.
Distal, smooth muscle oesophagus is innervated by preganglionic vagus nerve fibres from the dorsal motor nucleus.
Describe the involvment of neurotransmitter in oesophageal innervation
ACh affects 2 post-ganglionic neurons in the myenteric plexus: excitatory cholinergic neurons and inhibitory nitrinergic neurons via NO, VIP.
Ach, SP and Gastrin is involved in contraction, NO/VIP is involved in relaxation of the intrinsic sphincters. Coordinated contraction and relaxation using these= peristalsis
Describe swallowing of food and subsequent peristalsis
Skeletal muscle pushes bolus into pharynx. Food moves to oropharynx → laryngopharynx→oesophagus and stomach
Closure of glottis by epiglottis prevents food entering the trachea
The dorsal vagal nucleus and the nucleus ambiguus mediates peristalsis and sphincter relaxation.
Vagal efferent fibres communicate w myenteric neurons that relax the LOS. LOS closes after the food mass has passed
Why is secondary peristalsis important?
Large food material doesn’t reach the stomach after the 1st peristaltic wave
Distension of the lumen of the oesophagus by food stimulates receptors to repeat waves of secondary peristalsis
How does the LOS and the diaphragmatic sphincter prevent reflux?
LOS – closes after the food mass has passed
“Pinchcock” effect of the diaphragmatic sphincter on the lower oesophagus
How do mucosal folds in the cardia, and sphincter muscles of the UOS and LOS prevent reflux?
Mucosal folds in the cardia closes the lumen of the gastro-oesophageal junction:
Intrabdominal pa compresses intra-abdominal parts of the oesophagus. This creates a valve-like, oblique entry of oesophagus into stomach (adults only)
UOS and LOS = strong circular muscles which act as valves
Prevent reflux by forming an opening when relaxed and closing completely when contracted
Determine the main causes of swallowing difficulties
Oropharyngeal dysphagia- inability of the UOS to open or discoordination between the opening of UOS and the pharyngeal push behind ingested food
Oesophageal spasm- abnormal oesophageal contractions. Food isn’t reaching the stomach effectively
Diffuse oesophageal spasm- chest pain coming from oesophagus (angina-like)
What is the pathophysiology of achalasia?
Findings may vary:
Impaired LOS relaxation (spasms)
Impaired peristalsis (sphincter spasms)
Food and liquids fail to reach the stomach due to delayed opening of LOS
This causes bird’s beak appearance on an oesophagram
Initiating factor for this is thought to be autoimmune or infection
What are the symptoms of achalasia?
Dysphagia: difficult/painful swallowing
Vomiting/regurgitation
Heartburn due to:
oesophageal dysmotility
Retention of ingested (acidic) food
Lactic acid generation during decomposition of retained food;
Retention of gastric acid refluxed in the oesophagus due to poor emptying and incomplete LOS relaxation
What steps would you take to diagnose achalasia?
Take: patient history and evaluate any swallowing disorders
Some swallowing abnormalities may be frequent in elderly- eg swallowing slowly/coughing
Barium swallow shows oesophageal dilation w lower end beak deformity
Evaluate the entire swallowing channel (mouth, pharynx, and oesophagus)
Carry out oesophageal manometry: absent peristalsis in the body of the oesophagus.
Why should oesophageal manometry be carried out?
To determine the cause of non-cardiac chest pain
To evaluate the cause of reflux (GORD? Or achalasia?)
To determine the cause of swallowing difficulty (does UOS/LOS contract and relax in a coordinated fashion?)
How would you interpret the results of oesophageal manometry?
Normal LOS pa=15 mmHg, but when the LOS relaxes to let food into the stomach, pa is <10 mmHg
If LOS pa is < 10mmHg in the absence of food into the stomach, GORD can be suspected. Other manometric findings:
LOS fails to relax upon wet swallow (<75% relaxation)
LOS pa>100 is achalasia because the LOS fails to relax after swallowing. > 200 is nut cracker achalasia
Aperistalsis in oesophageal body
Relative increase in intra-oesophageal pa compared w intra-gastric pa
