The oesophagus and its disorders Flashcards
What is the anatomy of the oesophagus
-fubromuscular tube (25cm) of striated squamous epithelium
-lies posterior to the trachea
-begins at the end of laryngopharynx and joins the stomach a few cm from the diaphragm
What is the role of the oesophagus
1) transports food to the stomach
2) secretes mucus to trap pathogens
What promotes the transport of ingested food into the stomach
-this is a highly coordinated muscle process- involves the contraction and relaxation of the oesophagus which transports the food through the length of the GIT
-relaxation of the sphincters
What is the muscle structure of the oesophagus
-skeletal muscles surround the oesophagus below the pharynx.
-smooth muscle surround the lower two thirds
Describe the two oesophagus sphincters?
1) Upper oesophageal sphincter:
-striated muscle
-musculo-cartilaginous structure
-constricted to avoid air from entering the oesophagus
2) Lower oesophageal sphincter:
-smooth muscle; acts as a flop valve
-LOS= area of high pressure zone
-LOS has intrinsic and extrinsic components
Intrinsic= oesophageal muscles under neurohormonal influence
Extrinsic= diaphragm muscle
Explain intrinsic compounds of the LOS
-thick circular smooth muscle layers and longitudinal muscles
-clasp like semi-circular smooth muscle fibres on the right side
-myogenic activity but less Ach respnse
-sling like oblique gastric muscle fibres on the left side which work alongside with clasp like semicircular smooth muscle fibres—-> prevents regurgitation
Why is reflux common in infants
Angle of His is poorly developed for infants which makes a vertical junction with stomach- reflux is more common in infants
What are extrinsic components of LOS
-Crural diaphragm encircles the LOS
-forms channel through which oesophagus enters the abdomen
-fibres of the crural portion of the diaphragm possess a ‘pinchcock-like’ action (myogenic tone)
Explain the innervation of the oesophagus
Upper part:
-striated muscle—> supplied by somatic motor neurones of vagus nerve without interruption
-vagus nerve
-splanchnic nerve
Lower part:
-innervated by visceral motor neurons of vagus nerve with interruptions
-involvement of cholinergic and non cholinergic (NANC innervation) in the control of tone of the lower oesophageal sphincter
explain Neural control of the oesophageal sphincters
-oesophagus is also encircled by nerves of the oesophageal plexus
-acetylcholine: contract the intrinsic sphincters
-gastrin contracts the intrinsic sphincters
-NO and VIP: relax the intrinsic sphincters
List the different functions of the oesophagus
-swallowing
-conveys foods and fluids from the pharynx to the stomach
- afferent impulses in the glossopharyngeal (vagal reflex)
-integration of impules in the nucleus of tractus solitarius (NTS), NA and dorsal vagal nucleus.
-efferent impulses pass to the pharyngeal musculature, tongue, oesophagus and LOS
How is swallowing initiated
voluntarily action- collect material on tongue and push it backwards into pharynx
-waves of involuntary contractions push the material into oesophagus
Food moves from:
-mouth—-> oropharynx—> laryngopharynx—-> oesophagus—-> stomach
what are reflex responses when swallowing
-inhibition of respiration- nasopharynx is closed off
-closure of glottis by epiglottis
-prevents food from entering the trachea
How does food move towards the stomach
-ring of peristaltic waves behind the food mass moves it towards the stomach
Explain what the LOS does during swallowing
LOS opens and stays open throughout swallowing
What happens after the relaxation of the UOS as food passes
-UOS closes as soon as food passes
-glottis opens
-breathing resumes
-LOS closes after the food mass has passed
What does distension of the lumen of the oesophagus stimulate
Distention of the lumen of the oesophagus by food remnants stimulates the receptors—-> repeated waves of peristalsis
-secondary peristalsis ensures that ingested food reaches the stomach
What prevents the reflux of gastric contents
there is an anti-reflux barrier in the region of gastro-oesophageal junction:
1) LOS-closes after the food mass has passed
2) Pinchcock effect of the diaphragmatic sphincter on the lower oesophagus
3) Plug like action of the mucosal folds in the cardiac- occludes the lumen of the gastro-oesophageal junction:
-abdominal pressure acting on the intra abdominal parts of the oesophagus
-valve like effect of oblique entry of oesophagus into stomach
What do the sphincter muscles of UOS and LOS do
-act as valves: promotes and controls the movement of the food mass aborally
What are types of oesophageal disorders?
1) Oropharyngeal dysphasia- swallowing difficulty is caused by the inability of the UOS to open or disco ordination of the timing between opening of UOS and the pharyngeal push behind the ingested mass of food
2) oesophageal spasm- abnormal oesophageal contractions
3) diffuse oesophageal spasm- chest pain coming from oesophagus
4) achalasia- disorders of motility or peristalsis of oesophagus
5) regurgitation- reflux of stomach acids into oesophagus
Explain the pathophysiology of achlasia
-every 1 in 100, 000
Findings may vary:
-LOS spasms
-impaired peristalsis
-food and liquids fail to reach stomach
-results in dilation of oesophageal body with distal narrowing of the barium filled oesophagus on oesophagram.
Discuss the aetiology of achalasia
1) disorders of motility or peristalsis of oesophagus
2) damage to the innervation of oesophagus
3) degenerative lesions to the vagus nerve and loss of myenteric plexus ganglionic cells in the oesophagus
List some symptoms of achalasia
1) Difficulty swallowing (dysphasia)
2) vomiting
3) heartburn
Heartburn can be caused by:
-retention of ingested food
-generation of lactic acid in process of decomposition of retained food
-retrosternal burning sensation to due oesophageal dysmotility
How does someone diagnose something with achalasia
1) examine patient and take patient history (self report)
2) barium radiography- shows dilation of oesophagus with beak deformity at the lower end of
3) oesophageal manometry- absent peristalsis
