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sem 2 Liver and GI > Oesophagus and its disorders > Flashcards

Oesophagus and its disorders Flashcards

1
Q

Anatomy of the oesophagus

A

Fibromuscular tube (25cm) of striated squamous epithelium

Lies posterior to the trachea

Begins at end of laryngopharynx and joins stomach a few cm from diaphragm

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2
Q

roles of the oesophagus

A

transports food to the stomach and secretes mucus

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3
Q

where does food go after entering the mouth?

A
  1. throat (pharynx)
  2. upper oesophageal sphincter
  3. oesophagus
  4. lower oesophageal sphincter
  5. diaphragm
  6. stomach
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4
Q

as food approaches the upper oesophageal sphincter what happens?

A

the sphincter opens (relaxes) so food/bolus can enter the oesophagus

peristalsis (rhythmic waves) propel the food downwards, and the food passes through the lower oesophageal sphincter into the stomach

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5
Q

muscle structure of the oesophagus

A
  1. Skeletal muscles surround the oesophagus below the pharynx (the upper third)
  2. Smooth muscles surround the lower two thirds
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6
Q

2 oesophageal sphincters

A

Upper oesophageal sphincter

  • striated muscle, musculo-cartilaginous structure
  • constricted to avoid air entering the oesophagus

Lower oesophageal sphincter

  • smooth muscle; acts as a flap valve
  • area of high pressure zone, located where the oesophagus merges with the stomach
  • has intrinsic and extrinsic components
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7
Q

intrinsic components of the LOS

A
  1. Thick circular smooth muscle layers and longitudinal muscles
  2. Clasp-like semi-circular smooth muscle fibres on the right side
    - Myogenic activity, but less ACh-responsive
  3. Sling-like oblique gastric (angle of His) muscle fibres on the left side. Working with clasp like-semi-circular smooth muscle fibres to help prevent regurgitation- responsive to cholinergic innervation
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8
Q

extrinsic components of the LOS

A
  • crural part of the diaphragm encircles the LOS
  • forms a channel through which oesophagus enters the abdomen
  • fibres of the crural portion of the diaphragm possess a sphincter action (diaphragmatic sphincter, myogenic tone)
  • the diaphragm muscle functions as an adjunctive external sphincter which raises the pressure in the terminal oesophagus related to the movements of respiration
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9
Q

malfunction of intrinsic and extrinsic components causes what?

A

GORD

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10
Q

why is reflux common in infants?

A

because the angle of His is poorly developed in infants, as it makes a vertical junction with stomach

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11
Q

Neural control of the oesophageal sphincters

A

Acetylcholine, SP: contract the intrinsic sphincters

NO and VIP: relax the intrinsic sphincters

Extrinsic and intrinsic sphincters work in concert to push the food into the stomach

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12
Q

how does NO cause relaxation of smooth muscle cells?

A
  • NO interacts with AC
  • AC converts GTP to cGMP
  • cGMP activates PKG
  • PKG acts on myosin phosphatase on SM cells smooth muscle cells, causing SM relaxation

Myosin phosphatase = enzyme which dephosphorylates the regulatory chain of myosin II, undoing the muscle contraction process initiated by initiated by myosin light-chain kinase

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13
Q

Innervation of the oesophagus

A

Upper part: striated muscle; supplied by somatic motor neurons of vagus nerve without interruption
-vagus and splanchnic nerves

Lower part: smooth muscles;
innervated by visceral motor neurons of vagus nerve with interruptions

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14
Q

oesophagus is encircled by what?

A

nerves of

the oesophageal plexus

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15
Q

Dorsal vagal nucleus

A
  • a cranial nerve nucleus for the vagus nerve in the medulla
  • lies under the floor of the 4th ventricle
  • serves parasympathetic vagal functions in the GIT, lungs (and other thoracic and abdominal vagal innervations)
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16
Q

The phrenic nerve

A
  • nerve that originates in the neck
  • important for breathing – innervates the external and internal intercostal muscles and the diaphragm
  • passes motor information to the diaphragm and receives sensory information from it
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17
Q

Oesophageal motor innervation (slide 10 diagram)

A

Striated muscle of the upper oesophagus is innervated directly by the somatic efferent cholinergic fibres of the vagus nerve originating from the nucleus ambiguous

Smooth muscle of the distal oesophagus is innervated by the preganglionic vagus nerve fibres from the dorsal motor nucleus. ACh affects two types of post-ganglionic neurons in the myenteric plexus: excitatory cholinergic neurons via Ach and inhibitory nitrinergic neurons via NO, VIP

18
Q

Functions of the oesophagus - swallowing

A

Voluntary action – collect material on tongue and push it backwards into pharynx
Waves of involuntary contractions push the material into oesophagus

  1. excitation of receptors in the pharynx
  2. afferent impulses in the trigeminal, glossopharyngeal and vagus nerves travel to NTS, NA, DVN, impulses are integrated
  3. a programmed set of events from the dorsal vagal nucleus and the nucleus ambiguous mediates oesophageal peristalsis and sphincter relaxation
  4. efferent impulses pass to the pharyngeal musculature and the tongue (trigeminal, facial and hypoglossal nerves (tongue muscles)
  5. the vagal efferent fibres communicate with myenteric neurons that mediate relaxation of LOS (larger lower inset)
19
Q

Reflex responses to swallowing

A
  1. Inhibition of respiration (breathing)- nasopharynx is closed off
    - closure of glottis (around the vocal cords) by epiglottis, prevents food from entering the trachea
    - after swallowing, the epiglottis goes back to its original position and breathing resumes
  2. Ring of peristaltic waves (4cm/sec) behind the material moves it towards the stomach
    - a second wave of peristalsis moves any food remnants along
    - longitudinal muscles on the outside and circular muscles on the inside
20
Q

what moves food towards the stomach and along the GIT?

A

progressive muscular contractions and relaxations

21
Q

what stays open throughout swallowing?

A

LOS - closes after the material has passed

22
Q

has the majority of the food reached the stomach after the first peristaltic wave?

A

no, a large amount of food material does not reach the stomach after the first peristaltic wave

Stimulation of receptors upon distension of the lumen of the oesophagus by the food → repeated waves of peristalsis (secondary peristalsis)

23
Q

What prevents the reflux of gastric contents?

A
  1. LOS – closes after material has passed
  2. “Pinchcock” effect of the diaphragmatic sphincter on the lower oesophagus
  3. Abdominal pressure acting on the intra-abdominal parts of the oesophagus, Valve-like effect of oblique entry of oesophagus into stomach – in adults only
24
Q

What prevents the reflux of gastric contents?

A
  1. LOS – closes after material has passed
  2. “Pinchcock” effect of the diaphragmatic sphincter on the lower oesophagus
  3. -Abdominal pressure acting on the intra-abdominal parts of the oesophagus
    - Valve-like effect of oblique entry (angle of HIS) of oesophagus into stomach (in adults only)
25
Q

Types of oesophageal disorders

A
  1. Achalasia
  2. GORD, regurgitation
  3. Aphagia
  4. Oesophageal spasm
  5. Diffuse oesophageal spasm
26
Q

Achalasia

summary

A

Disorders of motility or peristalsis of oesophagus

-sphincter spasm, delayed emptying (relaxation) through the LOS, dilation of the oesophageal body with distal narrowing. long periods of sporadic dysphagia with regurgitation of food

could be due to:

  • degenerative lesions to the vagus nerve and loss of myenteric plexus ganglionic cells in the oesophagus
  • damage to the innervation of oesophagus

symptoms are dysphagia, vomiting and heartburn

diagnosis is through barium radiography, look at patients history, swallowing disorders, oesophageal manometry

27
Q

why might an oesophageal manometry be performed?

A

test evaluates if the oesophagus is contracting and relaxing properly

  • non cardiac chest pain
  • evaluate the cause of acid reflux
  • determine the cause of difficulty with swallowing food

a manometry will be ordered if you have symptoms of:

  • Heartburn or nausea after eating
  • Problems swallowing (Achalasia)
28
Q

results of an oesophageal manometry

A

high LOS pressure which fails to relax after swallowing
-Lack of a coordinated LOS relaxation in response to swallowing

abnormal results show

  • presence of muscle spasms in the oesophageal body
  • presence of weak contractions along the length of the oesophagus
29
Q

Reflux in normal individuals

A
  • brief, infrequent
  • often occurs after meals in normal individuals, spontaneous LOS relaxation
  • usually stimulates salivation, saliva is a natural antacid - dilutes and neutralises refluxed gastric contents
30
Q

what will a low rate rate of saliva/lack of ability to swallow own saliva mean?

A

prolongation of contact of refluxed material with oesophagus

31
Q

Gastro-oesophageal reflux disease (GORD)

A

when reflex is more frequent and troublesome
-causes a burning sensation in chest after meals

maybe due to low rate of salivation/lack of ability to swallow own saliva →prolongation of contact of refluxed material with oesophagus
→ oesophageal irritation and oesophageal damage

32
Q

Causes of reflux in those with GORD

A
  1. Transient spontaneous LOS relaxation
  2. Resting LOS pressure is too weak to resist the pressure within the stomach
  3. Sudden relaxation of the LOS that is not induced by swallowing
33
Q

Factors that contribute to the severity of GORD

A
  • weak/uncoordinated oesophageal contractions
  • length of time the oesophagus is exposed to gastric acid
  • amount of pressure placed on the anti-reflux barrier
34
Q

Factors associated with GORD:

A

Pregnancy or obesity
Fat, chocolate, coffee or alcohol ingestion
Large meals, tomatoes, orange juice, onions, etc.
Cigarette
Drugs (e.g. Anticholinergic agents, calcium channel blockers and nitrate drugs)

35
Q

symptoms of GORD

A

Resting LOS tone is low or absent, and this tone fails to increase when lying flat or during pregnancy

Poor oesophageal peristalsis leads to a decrease in the clearance of acid

Hiatus hernia

Delayed gastric emptying

cause the following:

  1. Heartburn and acid regurgitation
  2. Wake up at night – reflux irritates the larynx
  3. Dysphagia
36
Q

Investigating GORD

A
  • Upper GI endoscopy
  • Manometry

-24-hr ambulatory pH monitoring
24 hr hour pH monitoring shows that most normal individuals (non-refluxers) reflux on a daily basis -therefore, GORD implies not just the presence of reflux, but reflux in excess of that experienced by non-refluxers

37
Q

Pregnancy and GORD

A
  • Foetus increases pressure on abdominal contents
  • Pushes terminal segments of oesophagus into thoracic cavity
  • Last trimester of pregnancy is associated with increased abdominal pressure and this forces gastric contents into oesophagus
  • Heartburn subsides in the last months of pregnancy as uterus descends into pelvis
38
Q

Heartburn in the absence of pregnancy

A
  • May occur in some individuals upon eating large meals
  • Less efficient LOS
  • Gastric contents episodically refluxed into oesophagus, causing heartburn
  • Ulcer, scarring, obstruction or perforation of lower oesophagus
39
Q

Potential long term effects of GORD

A

Oesophagitis, oesophageal strictures
Squamous cell carcinoma
Barrett’s syndrome - this may predispose someone to oesophageal adenocarcinoma
Oesophageal ulcer

40
Q

Management and drug treatment of GORD

for full list of lifestyle changes look at slide 38

A

Life-style changes - raise head of bed at night, weight loss, stop smoking

↓ Intake of foods and drink which cause symptoms (avoid foods that increase gastric acidity/slow gastric emptying/fatty foods)

Anti-reflux surgery (fundoplication – wrap fundus around LOS). Fundoplication can cause dysphagia as it reduces the distensibility of LOS

Take antacids
H2 receptor antagonists and proton pump inhibitors

Metoclopramide/domperidone – may enhance peristalsis and help gastric acid clearance

41
Q

Use of antacids in the treatment of GORD

A

Neutralise gastric acid; ↑ pH of gastric lumen
Inhibit peptic activity and stop acid secretion

But
Magnesium salts→ diarrhoea
Aluminium salts→ constipation
Use a mixture of 2 to ensure bowel function
Combine alginates (e.g. gaviscon) with antacids for oesophageal reflux
Alginic acid + saliva form a raft which floats on content of gastric lumen and protects the oesophageal mucosa from reflux

All of the above agents ↓ acid secretion and help heal the ulcer, but removal of H. pylori is essential to stop ulcer returning.

sem 2 Liver and GI (11 decks)

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