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Physiology 1 Semester 2 > The Oesophagus and its Disorders > Flashcards

The Oesophagus and its Disorders Flashcards

1
Q

Describe the anatomy of the oesophagus

A
  • Fibromuscular tube of striated squamous epithelium
  • Lies posterior to the trachea
  • Begins at the end of the laryngopharynx and joins the stomach a few cm from the diaphragm (at the cardiac orifice of the stomach)
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2
Q

Describe the basic functions of the oesophagus

A
  • Transports food to the stomach
  • Secretes mucus - allows transport to occur at a faster rate by lubricating the oesophagus and also prevents damage to the tissue
  • There is a highly coordinated muscular process to transport food down the oesophagus which involves contraction and relaxation of the oesophagus which transports the food through the length to the GI tract
  • Relaxation of the upper and lower esophageal sphincters is needed for food to pass into the stomach
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3
Q

Describe the muscular structure of the oesophagus

A
  • Skeletal muscles surround the oesophagus below the pharynx (the upper third of the oesophagus)
  • There is smooth muscle surrounding the bottom ⅔ rds of the oesophagus
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4
Q

State the name of and describe the structure of the 2 oesophageal sphincters

A
  1. The upper oesophageal sphincter - striated muscle
    - Musculo-cartilaginous structure
    - Constricted to avoid air entering the oesophagus
  2. Lower oesophageal sphincter - smooth muscle
    - Acts as a flap valve
    - It is an area of high pressure
    - Has intrinsic and extrinsic components
    - Intrinsic components- oesophageal muscles, under neurohormonal influence - neuronal = vago vagal reflex, hormonal = gastrin etc
    - Extrinsic components - diaphragm muscle (adjunctive external sphincter)
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5
Q

What does malfunction of the intrinsic/extrinsic components lead to?

A

GORD (gastroesophageal reflux disease)

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6
Q

Describe the 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 (some resting tone is initiated by cells) but less acetylcholine responsive
  3. Sling like oblique gastric (angle of his) muscle fibres on the left side - work in concert with clasp like semi circular smooth muscle fibres to help prevent regurgitation - responsive to cholinergic innervation
    The angle of His is poorly developed in infants as it makes a vertical junction with the stomach hence why reflux is common in infants
  • Contraction is mediated by acetylcholine
  • Relaxation is mediated by VIP and NO
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7
Q

Describe the extrinsic components of the LOS

A
  • Crural diaphragm encircles the lower oesophageal sphincter
  • Forms a channel through which the oesophagus enters the abdomen
  • Fibres of the crural portion of the diaphragm possess a ‘pinchcock like’ action - the extrinsic components have myogenic tone
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8
Q

Describe how the oesophagus is innervated including neural control

A

Innervation of the oesophagus -
- Upper part - striated muscle supplied by somatic motor neurons of the vagus nerve without interruption - vagus nerves and splanchnic nerves
- Lower part - smooth muscles - innervated by visceral motor neurons of vagus nerves with interruptions - these synapse with postganglionic neurons - cell bodies in oesophagus and splanchnic plexus - acetylcholine, VIP and NO have large role in these nerves

Neural control of oesophageal sphincters -
- There is involvement of cholinergic nerves via acetylcholine and non cholinergic nerves - NANC innervation controls tone in the lower oesophageal sphincter
- Oesophagus is also encircled by nerves of the oesophageal plexus
- Acetylcholine contracts the intrinsic sphincters
- NO and VIP relax the intrinsic sphincters

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9
Q

What are the functions of the oesophagus?

A
  • Swallowing
  • Conveys food and fluids from pharynx to stomach
  • Swallowing is triggered by the presence of food in the mouth
  • There are afferent impulses in the glossopharyngeal vagal reflex
  • Integration of impulses in the nucleus tractus solitarius, nucleus ambiguous and dorsal vagal nucleus
  • Efferent impulses/motor pathways pass to the pharyngeal musculature, tongue, oesophagus and lower oesophageal sphincter
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10
Q

Describe how swallowing is initiated and the reflux responses that occur during swallowing

A
  1. Voluntary action - collect material on tongue and push it backwards into the pharynx via skeletal muscles and use mucus membranes to lubricate the food
  2. Waves of involuntary contractions push the material into the oesophagus
    Food moves from mouth -> oropharynx -> laryngopharynx -> oesophagus -> stomach

Reflex responses -
- Inhibition of respiration (breathing) - nasopharynx is closed off
- Closure of the glottis around the vocal cords by epiglottis
- Prevents food from entering the trachea
- Ring of peristaltic waves behind the food mass move it towards the stomach
- A second wave of peristalsis moves any food remnants along the oesophagus

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11
Q

Describe secondary peristalsis

A

Upon relaxation of the upper oesophageal sphincter food passes -
- The upper oesophageal sphincter closes as soon as food has passed
- The glottis opens and breathing resumes
- Large food material does not often reach the stomach after the first peristaltic wave
- Distension 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

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12
Q

Describe what prevents the reflux of gastric contents

A

There is an anti reflux barrier in the region of the gastroesophageal junction

  1. Lower oesophageal sphincter closes after the food has passed
  2. Pinchcock effect of the diaphragmatic sphincter on the lower oesophagus
  3. Plug like action of the mucosal folds in the cardia - occludes the lumen of the gastroesophageal junction -
    - Abdominal pressure acting on the intra abdominal parts of the oesophagus
    - Valve like effect of oblique entry of oesophagus into stomach
  4. Sphincter muscles of UOS and LOS are strong circular muscles
    - Act as valves - promotes and controls movement of food mass aborally (towards the anus)
    - Prevent reflux by closing completely when contracted and only opening when needed
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13
Q

State and describe briefly the types of oesophageal disorders

A

Oropharyngeal dysphagia/aphagia - swallowing difficulty is caused by the inability of the upper oesopharyngeal sphincter to open or discoordination of the timing between the opening of the UOS and the pharyngeal push behind the ingested mass of food

Oesophageal spasm - abnormal oesophageal contractions and food is not reaching the stomach effectively

Diffuse oesophageal spasm - chest pain coming from oesophagus (angina like pain)

Achalasia - disorders of motility of peristalsis of oesophagus (assess the motor function of the UOS, LOS and esophageal body)

Regurgitation - reflux of stomach acids into the oesophagus due to a weak LOS (GORD) - assess cause of regurgitation

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14
Q

Describe the pathophysiology of achalasia

A

1 in 100,000 - presents at any age

Findings may vary -
- Impaired lower oesophageal sphincter e.g. spasms
- Can be accompanied by impaired peristalsis (sphincter spasms)
- Food and liquids may fail to reach the stomach due to delayed opening of the LOS
- Results in dilation of oesophageal body with distal narrowing of the barium - filled oesophagus on oesphagram
- There is a long period of sporadic dysphagia (difficulty swallowing)
- Regurgitation of food

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15
Q

Describe the aetiology of achalasia

A
  1. Disorders of motility or peristalsis of oesophagus
  2. Damage to the innervation of oesophagus
  3. Degenerative lesions on the vagus nerves and loss of myenteric plexus ganglionic cells in oesophagus

The initiating factor is unknown but thought to be autoimmune or triggered by infection

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16
Q

State the symptoms of achalasia and describe H_________ in more detail

A
  1. Dysphagia - difficult/painful swallowing
  2. Vomiting/regurgitation
  3. Heartburn
    - This is a retrosternal burning sensation due to oesophageal dysmotility
    - Retention of ingested acidic foods
    - Generation of lactic acid in the process of decomposition of retained food
    - Can also be caused by a retention of small quantities of gastric acid refluxed in the oesophagus due to poor emptying and incomplete relaxation of LOS
17
Q

Describe how achalasia is diagnosed

A
  • Examine/take patient history and evaluate any swallowing disorders
  • The patients self report may suggest the type of disorder responsible for the complaints which may trigger tests required to determine or verify the specific cause of the complaint
  1. Barium radiography (barium swallow) - dilatation of oesophagus with beak deformity at lower end - evaluates the entire swallowing channel - mouth, pharynx and oesophagus
  2. Oesophageal manometry - absent peristalsis
18
Q

Describe why we would perform a oesophageal manometry and what different results mean

A

Performed for the following reasons -
1. To determine the cause of non cardiac chest pain
2. To evaluate the cause of reflux (regurgitation) of stomach acid and other contents back up into the oesophagus
3. To determine the cause of a difficulty in swallowing food (does the UOS/LOS contract and reflex properly?)

Overall tests if the oesophagus is contracting and relaxing properly
- Pressure of LOS less than 26 mmHG is normal, higher than 100 mmHG is achalasia and more than 200 mmHg is nutcracker achalasia
- Low LOS pressure suggests GORD but it can occur in individuals with normal LOS pressure

19
Q

Describe what normal results of oesophageal manometry

A
  • Normal LOS pressure and normal muscle contractions upon swallowing
  • The muscle contractions follow a normal pattern down the oesophagus
  • Normal pressure of the LOS is about 15 mmHg - When the LOS relaxes to let food pass into the stomach the pressure is less than 10 mmHg
20
Q

Describe what abnormal results of oesophageal manometry

A
  • In the absence of letting food mass pass through the LOS into the stomach and the LOS pressure is less than 10 mmHg then GORD may be suspected
  • Presence of muscle spasms in the oesophageal body
  • Presence of weak contractions along the length of the oesophagus
  • Achalasia is characterised by high LOS pressure - the LOS fails to relax after swallowing
  • Lack of coordinated LOS relaxation in response to swallowing
21
Q

What is reflux like in normal individuals

A
  • Reflux is often brief and relatively infrequent
  • Often occurs after meals in normal individuals
  • Reflux usually stimulates salivation
  • Saliva is an effective natural antacid - dilutes and neutralises refluxed gastric acid
22
Q

What does a low rate of salivation lead to?

A
  • Lack of ability to swallow own saliva
  • Causes a prolongation of contact of refluxed material with oesophagus leading to GORD
23
Q

Describe what GORD is

A
  • GORD is the retrograde movement of gastric content into oesophagus due to prolonged relaxation of the LOS
  • GORD is when reflux is more frequent and troublesome
  • GORD causes a burning sensation in the chest after meals
  • It causes oesophageal irritation and oesophageal damage
24
Q

What are the 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 and sustained relaxation of the LOS that is not induced by swallowing
25
Q

State and describe the factors that contribute to the severity of GORD

A
  1. Weak or uncoordinated oesophageal contractions/poor oesophageal motor activity - prolonged duration of contact of refluxed digestive contents with the oesophagus
  2. Length of time the oesophagus is exposed to gastric acid - increased gastric acid secretion coupled with the presence of bile in gastric contents causes severe oesophageal damage
  3. Amount of pressure placed on the anti reflux barrier
    - Reflux occurred after eating, lying down and when there is delayed gastric emptying
26
Q

What are factors associated with GORD

A
  • Pregnancy or obesity
  • Food - fat, chocolate, coffee, large meals, tomatoes, orange juice, onions
  • Drugs - anticholinergic agents, calcium channel blockers and nitrate drugs, alcohol ingestion and cigarettes
27
Q

Explain the pathophysiology and clinical features of GORD

A
  • Resting LOS tone is low or absent
  • LOS tone fails to increase when lying flat or during pregnancy
  • Poor oesophageal peristalsis causes a decreased clearance of acid
  • A hiatus hernia (impairs the functioning of LOS and diaphragm closing mechanisms)
  • Delayed gastric emptying
28
Q

What are the symptoms of GORD?

A
  • Heartburn and acid regurgitation
  • Wake up at night - reflux irritates the larynx
  • Dysphagia
29
Q

How is GORD investigated?

A
  • Low dose proton pump inhibitor
  • Upper GI endoscopy
  • Manometry
  • 24 hr ambulatory pH monitoring
30
Q

What can be found from 24 hr pH monitoring?

A
  • 24 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
31
Q

Explain how pregnancy effects GORD

A
  • Last trimester of pregnancy is associated with an increases abdominal pressure which forces gastric contents into oesophagus
  • Foetus increases pressure on the abdominal contents - pushes terminal segments of the oesophagus into the thoracic cavity
  • Heartburn subsides in the last months of pregnancy as the uterus descends into the pelvis
32
Q

Why does heartburn happen in those that aren’t pregnant?

A
  • May occur in some individuals upon eating large meals
  • Less functional LOS
  • Gastric contents episodically refluxed into oesophagus
  • Heartburn, Ulcer, scarring, obstruction or perforation of lower oesophagus
33
Q

How is GORD managed?

A
  • Lifestyle changes - raising the head of the bed at night, weight loss, modifying food
  • Decreased intake of foods and drink which causes symptoms
  • Anti reflux surgery - wrapping the stomach fundus around the LOS
  • Antacids
  • H2 receptor antagonists and proton pump inhibitors
  • Metoclopramide/domperidone - may enhance peristalsis and help gastric acid clearance
34
Q

What are some lifestyle changes that can help to alleviate GORD

A
  • Some people need to avoid large meals
  • Lose weight if overweight
  • Avoid foods that increase gastric acidity
  • Avoid foods that slow gastric emptying (decrease fats intake)
  • Avoid lying down after meals - elevate the head of the bed
  • Avoid some drugs and smoking
35
Q

What do antacids go in GORD?

A
  • Neutralises gastric acid, increasing the pH of the gastric lumen
  • Inhibits peptic activity and stops acid secretion
36
Q

What is the problem with different types of antacids?

A
  • Magnesium salts cause diarrhoea
  • Aluminium salts cause constipation
37
Q

How are these problems overcome?

A
  • Use a mixture of 2 to ensure bowel function
  • Combine alginates e.g. gaviscon with antacids for oesophageal reflux
  • Alginic acid and saliva forms a raft which floats on content of gastric lumen and protects the oesophageal mucosa from reflux

All of the above decrease acid secretion and help heal ulcers but removal of H pylori bacterium is essential to stop the ulcer returning

38
Q

What are some potential complications of GORD

A
  • Oesophagus has squamous mucosa
  • Acid reflux - desquamation of esophageal cells - Injury of squamous mucosa
  • Increased cell loss leads to basal cell hyperplasia
  • Excessive desquamation leads to ulceration
  • Ulcers may haemorrhage perforate or heal by fibrosis with strictures
  • Leads to barrett’s oesophagus and oesophageal cancer
39
Q

State some potential long term effects of GORD

A
  • Oesophagitis, oesophageal strictures
  • Squamous cell carcinoma
  • Barrett’s syndrome - may predispose oesophageal adenocarcinoma
  • Oesophageal ulcer

Physiology 1 Semester 2 (50 decks)

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