Oesophagus and its disorders

Question 1

Anatomy of the oesophagus

Answer 1

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

Question 2

roles of the oesophagus

Answer 2

transports food to the stomach and secretes mucus

Question 3

where does food go after entering the mouth?

Answer 3

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

Question 4

as food approaches the upper oesophageal sphincter what happens?

Answer 4

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

Question 5

muscle structure of the oesophagus

Answer 5

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

Question 6

2 oesophageal sphincters

Answer 6

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

Question 7

intrinsic components of the LOS

Answer 7

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

Question 8

extrinsic components of the LOS

Answer 8

• 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

Question 9

malfunction of intrinsic and extrinsic components causes what?

Answer 9

GORD

Question 10

why is reflux common in infants?

Answer 10

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

Question 11

Neural control of the oesophageal sphincters

Answer 11

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

Question 12

how does NO cause relaxation of smooth muscle cells?

Answer 12

• 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

Question 13

Innervation of the oesophagus

Answer 13

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

Question 14

oesophagus is encircled by what?

Answer 14

nerves of

the oesophageal plexus

Question 15

Dorsal vagal nucleus

Answer 15

• 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)

Question 16

The phrenic nerve

Answer 16

• 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

Question 17

Oesophageal motor innervation (slide 10 diagram)

Answer 17

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

Question 18

Functions of the oesophagus - swallowing

Answer 18

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)

Question 19

Reflex responses to swallowing

Answer 19

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

Question 20

what moves food towards the stomach and along the GIT?

Answer 20

progressive muscular contractions and relaxations

Question 21

what stays open throughout swallowing?

Answer 21

LOS - closes after the material has passed

Question 22

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

Answer 22

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)

Question 23

What prevents the reflux of gastric contents?

Answer 23

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

Question 24

What prevents the reflux of gastric contents?

Answer 24

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)

Question 25

Types of oesophageal disorders

Answer 25

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

Question 26

Achalasia | summary

Answer 26

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

Question 27

why might an oesophageal manometry be performed?

Answer 27

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)

Question 28

results of an oesophageal manometry

Answer 28

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

Question 29

Reflux in normal individuals

Answer 29

- 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

Question 30

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

Answer 30

prolongation of contact of refluxed material with oesophagus

Question 31

Gastro-oesophageal reflux disease (GORD)

Answer 31

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

Question 32

Causes of reflux in those with GORD

Answer 32

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

Question 33

Factors that contribute to the severity of GORD

Answer 33

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

Question 34

Factors associated with GORD:

Answer 34

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)

Question 35

symptoms of GORD

Answer 35

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

Question 36

Investigating GORD

Answer 36

- 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

Question 37

Pregnancy and GORD

Answer 37

- 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

Question 38

Heartburn in the absence of pregnancy

Answer 38

- 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

Question 39

Potential long term effects of GORD

Answer 39

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

Question 40

Management and drug treatment of GORD | for full list of lifestyle changes look at slide 38

Answer 40

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

Question 41

Use of antacids in the treatment of GORD

Answer 41

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.