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Flashcards in The Oesophagus and its Disorders Deck (34)
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1

Describe the anatomy of the oesophagus.

  • It is a fibromuscular tube (25 cm) of striated squamous epithelium.
  • It lies posterior (behind) to the trachea.
  • It begins at the end of the laryngopharynx and joins the stomach a few centimetres from the diaphragm (at the cardiac orifice of the stomach).
  • It is found just beneath a structure called the cricoid cartilage (it is the soft tissue which usually anastesiats press down when they are carrying out sellick maneuver).

Sellick maneuver meaning - It is a technique used in endotracheal intubation to try to reduce the risk of regurgitation.

2

What promotes the transport of ingested food into the stomach?

  • The oesophagus transports food to the stomach (so its called the eating gullet).
  • It secretes mucus that helps to lubricate the inside of the oesophagus to prevent abrasion or damage (However the lining of the oesophagus is not as well protected as the stomach itself).
  • This is a highly coordinated muscular process and it involves contraction and relaxation of the oesophagus (initated by the presence of food in the pharynx) and transports the food through the GIT.
  • The upper part of the oesophagus has a sphincter (called the UOS) which will relax to allow the food to go through and then will close immediately to prevent the air from entering the oesophagus.
  • Simiilarly the there is a LOS that allows the passage of a swallowed bolus to the stomach and prevents the reflux of gastric contents into the oesophagus.

3

Describe the muscular structure of the oesophagus. What are the two sphincters of the oesophagus?

  • Skeletal muscles surround the oesophagus below the pharynx (in the upper third part).
  • Smooth muscles surround the lower two thirds of the oesophagus.

The oesophagus has two sphincters: -

  1. UOS (upper oesophageal sphincter) - 
    • It is a striated muscle and has a musculo-cartilaginous structure.
    • It is constricted to avoid air entering the oesophagus.
  2. LOS (lower oesophageal sphincter) -
    • It is a smooth muscle and acts like a flap valve.
    • It is a high-pressure zone (as it is closely located near the stomach that is filled with food).
    • The LOS has extrinsic and intrinsic components to it. The intrinsic component is the oesophageal muscles, under neurohormonal influence [eg. NO (for relaxation), Ach controls the level of constriction, VIP]. The extrinsic component is the diaphragm muscle (that act as adjunctive external sphincters).

4

Describe the components of the LOS.

The LOS has intrinsic and extrinsic components:-

  • INTRINSIC COMPONENTS: -
    1. Thick, circular smooth muscle layers and longitudinal muscle layers.
    2. Clasp-like, semicircular smooth muscle fibres (on the right-hand side). They have myogenic activity (so some resting tone) but is less ACh-responsive.
    3. Sling-like, oblique gastric muscle fibres on the left-hand side (they form the angle of His). They work in concert with the clasp-like smooth muscle fibres to help prevent regurgitation. They are 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.
  • EXTRINSIC COMPONENTS: -
    1. The crural diaphragm encircles the LOS, and forms a channel through which the oesophagus enters the abdomen.
    2. The fibres of the crural portion of the diaphragm posses a 'pinchcock-like' action (they are external sphincter) to stop any reflux of acidic chyme into the oesophagus. They have a myogenic tone.

5

Describe the innervation of the oesophagus (with regard to its sphincters).

  • Involvement of cholinergic (i.e. via ACh) and non-cholinergic innervation (NANC) [i.e. VIP and NO] which are very important in the relaxant properties associated with the oesophagus.
  • Neural control of the oesophageal sphincters consists of :-
    • Acetylcholine, SP: contraction of intrinsic sphincters.
    • NO, VIP: relax the intrinsic sphincters.

6

Describe the neural innervation of the oesophagus.

  • UPPER PART made up of STRIATED MUSCLE which supplied by somatic motor neurons of the vagus nerve without interruptions (so the information passes through the vagus and splanchnic nerve).
  • LOWER PART made up of SMOOTH MUSCLE which are innervated by visceral motor neurons of the vagus nerve with interruptions. These synapse with postganglionic neurons, cell bodies in the oesophagus and splanchnic plexus.
  • Oesophagus is also encircled by nerves of the oesophageal plexus.

Plexus meaning - It is a network of nerves or vessels in the body.

7

Describe oesophageal motor innervation.

  • The striated muscle of the upper oesophagus is innervated directly by the somatic efferent cholinergic fibres of the vagus nerve, originating from the nucleus ambiguus (releasing stimulatory ACh).
  • The smooth muscle of the 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 and inhibitory nitrinergic neurons via NO and VIP.

8

List some functions of the oesophagus.

  • Swallowing (deglutition).
  • Conveys food and fluids from the pharynx to the stomach.

9

Describe the coordination of swallowing.

  • Swallowing is triggered by afferent impulses in the trigeminal, glossopharyngeal (it is important for taste) and vagus nerves.
  • The efferent impulses pass to the pharyngeal musculature and the tongue (the trigeminal, facial and hypoglossal nerves supply the tongue muscles).
  • The integration of these impulses occurs in the nucleus tractus solitarius (NTS), the nucleus ambiguus (NA) and the dorsal vagal nucleus (DVN).

Trigeminal nerves meaning - It is a nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the largest of the cranial nerves.

10

How is swallowing initiated?

  1. The first process is VOLUNTARY actions, where we collect material on the tongue and push it backwards into the pharynx.
  2. Waves of INVOLUNTARY contractions then push the material into the oesophagus.

Food moves from Mouth → oropharynx → laryngopharynx → oesophagus and stomach.

11

What events occur during swallowing?

  • Inhibition of respiration (breathing), so the nasopharynx is closed off.
  • The epiglottis will fold over and close the glottis (around the vocal cords), which prevents the food from travelling into the trachea.
  • A ring of peristaltic waves (4cm/sec) behind the material move it towards the stomach.
  • A second wave of peristalsis moves any food remnants along.

12

Give information on secondary peristalsis.

  • Relaxation of upper oesophageal sphincter (UOS) allows the food to pass through.
  • UOS closes as soon as food passes and the glottis will open and breathing resumes.
  • Lower oesophageal sphincter opens and stays open throughout swallowing.
  • LOS closes after material has passed.

13

Why is secondary peristalsis necessary?

  • A large amount of food material does not reach the stomach after the first peristaltic wave.
  • Hence, there is stimulation of receptors upon distention of the lumen of the oesophagus by the food, which causes repeated waves of peristalsis, aka. secondary peristalsis.

14

What prevents the reflux of gastric contents?

  1. LOS closes after material passes.
  2. The 'pinchcock' effect of the diaphragmatic sphincter on the lower oesophagus (side-to-side compression between “2 pillars” of the crus).
  3. The plug-like action of the mucosal folds (called rugae) in the cardia.
  • Sphincter muscles of EOS and LOS = strong circular muscles; act as valves to control the movement of the food mass aborally (forward direction); prevent reflux by forming an opening when relaxed and closing completely when contracted.

15

What are the types of oesphageal disorders?

  1. Achalasia - It is a condition that affects the nerves and muscles of the oesophagus (food pipe), mainly at the lower end where it meets the stomach. This can lead to difficulty in swallowing (assess the motor function of the UOS, LOS and oesophageal body).
  2. Gastro-oesophageal reflux disease (GORD) - It is a condition where acid from the stomach leaks up into the oesophagus. Regurgiation occurs (can be due to weak LOS).
  3. Aphasia - It is the inability or refusal to swallow.
  4. Oesophageal spasm - It is a condition where there are irregular, uncoordinated, and sometimes powerful oesophageal contractions and food does not effectively reach the stomach.
  5. Diffuse oesophageal spasm - It is a condition where there is uncoordinated contractions of the esophagus, which may cause difficulty swallowing. It may cause chest pain coming from the oesophagus (it may be likened to angina).

16

Expand on the pathophysiology of achalasia.

  • Impaired LOS relaxation (so spasms occur).
  • Can be accompanied by impaired peristalsis (sphincter spasms).
  • Foods and liquids fail to reach the stomach (delayed opening of LOS).
  • This results in dilatation of the oesophageal body with distal narrowing (called bird’s beak appearance) of the barium-filled oesophagus (on oesophagram).
  • Long periods of sporadic dysphagia (difficulty swallowing).
  • Regurgitation of food.

17

List some causes of achalasia.

  • Disorders of motility or peristalsis of the oesophagus (assess the motor function of the UOS, LOS and oesophageal body).
  • Damage to the innervation of the oesophagus.
  • Degenerative lesions of the vagus nerve, and loss of the myenteric plexus (as it is quite important for contractions and relaxations) ganglionic cells in the oesophagus.
  • Initiating factor unknown, but thought to be autoimmune or triggered by infection.

18

List some symptoms of achalasia.

  • Dysphagia - Difficult or painful swallowing.
  • Vomiting.
  • Heartburn - It could be caused by the retention of small quantities of acid refluxed in the oesophagus due to poor emptying and incomplete relaxation of LOS.

19

What are two tests used in the diagnosis of achalasia?

  1. BARIUM RADIOGRAPHY: (barium swallow)
    • It allows for the evaluation of the entire swallowing channel (mouth, pharynx and oesophagus).
    • If there is a dilatation of oesophagus with beak deformity at lower end it indicatesthat the person has achalasia.
  2. OESOPHAGEAL MANOMETRY:
    • Checks to see if the oesophagus is contracting relaxing properly (checks for absent peristalsis).

20

Why is oesphageal manometry performed?

Oesophageal manometry is 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 (to check for the possibility of GORD).
  3. To determine the cause of difficulty with swallowing food (you can investigate if the UOS/LOS contract and relax properly).
    • Allows evaluation of strength of coordination of muscle contractions.
    • Relaxation function of LOS.

Overall, test evaluates if the oesophagus is contracting and relaxing properly (To do the test you just swallow water).

21

What different diseases do different LOS pressures indicate?

  • Low LOS pressure suggests GORD (because if the pressure is low it means that material within the gut can pass through)[although GORD can occur in individuals with normal LOS pressure].
  • High LOS pressure suggests achalasia.
  • <26 mmHg = normal.
  • >100 mmHg = achalasia.
  • >200 mmHg = nut-cracker achalasia.

22

What do the results of oesophageal manometry suggest in each case?

  • Normal results of an oesophageal manometry would show: -
    • The pressure of the muscle contractions that move food down the oesophagus is normal.
    • The muscle contractions follow a normal pattern down the oesophagus.
    • Normal pressure of the LOS is about 15 mmHg, but when the LOS relaxes to let food pass into the stomach, the pressure is less than 10 mmHg.
  • Abnormal results show/are characterised by: -
    • The presence of muscle spasms in the oesophageal body.
    • The presence of weak contractions along the length of the oesophagus.
    • The LOS pressure is less than 10 mmHg (GORD?) – do not confuse these 2.
    • Characterised by high LOS pressure which fails to relax after swallowing.

23

Describe reflux in normal individuals.

  • It is the retro-grade movement of gastric content into oesophagus, due to relaxation of the LOS.
  • The reflux is often brief, and relatively infrequent.
  • It often occurs after meals in normal individuals (due to transient spontaneous LOS relaxation, aka TSR).
  • The reflux usually stimulates salivation.
  • Saliva is an effective natural antacid. It dilutes and neutralises the refluxed gastric contents.
  • Low rate of salivation is quite problematic and if you cant swallow your own saliva it could lead to prolonged contact of refluxed material with oesophagus.

24

What is GORD?

  • GORD stands for Gastro-Oesophageal Reflux Disease.
  • It is when reflux is more frequent and troublesome.
  • Causes a burning sensation in chest after meals (angina-like pain?).
  • Also, there is sometimes a low rate of salivation.
  • This leads to a lack of ability to swallow own saliva, which leads to the prolongation of contact of the refluxed material with the oesophagus.
  • This results in oesophageal irritation and oesophageal damage.

25

List some causes of reflux in those with GORD.

  1. Transient spontaneous LOS relaxation (TSR)
    • 98% of reflux events in normal individuals is associated with   transient spontaneous relaxation (tsr) of LOS.
  2. Resting LOS pressure is too weak to resist the pressure within the stomach (so material can enter the oesophagus).
  3. Sudden relaxation of the LOS that isn't induced by swallowing.

But tsr accounts for only about 60% of reflux events in patients with reflux, the remaining times it occurs due to a malfunction of the anti-reflux barriers.

26

What are some factors that could contribute to the severity of GORD?

  1. Weak or uncoordinated oesophageal contractions.
  2. Length of time the oesophagus is exposed to gastric acid (greater gastric acid secretion coupled with presence of bile in gastric contents can lead to severe oesophageal damage).
  3. Amount of pressure placed on the anti-reflux barrier (especially in pregnant women).

Reflux occurs after eating, lying down (supine), and when there is delayed gastric emptying.

27

What are some factors associated with the cause of GORD?

GORD is caused by following:

  • Reflux of gastric contents through the LOS (acid or bile).
  • Chronic oesophagitis (erosive or non-erosive)
  • Overall the GORD prevalence is 30%.

Factors associated with GORD:-

  • Pregnancy/obesity.
  • Fat, chocolate, coffee or alcohol ingestion.
  • Large meals, tomatoes, orange juice, onions, etc.
  • Cigarettes.
  • Drugs (eg. anticholinergic agents, calcium channel clockers and nitrate drugs).

28

Describe the pathophysiology of gourd. What are some symptoms of GORD?

  • Resting LOS tone is low or absent (a low or absent tone means that gut contents can be pushed into the oesophagus).
  • LOS tone fails to increase when lying flat or during pregnancy.
  • Poor oesophageal peristalsis can decrease the clearance of acid (this can lead to increased contact of the acid with the oesophagus).
  • A hiatus hernia (impairs the functioning of LOS and diaphragm closing mechanisms).
  • Delayed gastric emptying.

Symptoms:-

  • Heartburn and acid regurgitation.
  • Waking up at night (the reflux irritates the larynx).
  • Dysphagia (difficulty swallowing).

29

How would you investigate GORD?

  • Low dose proton pump inhibitor (PPI) challenge is 1st line.
  • Upper GI endoscopy.
  • Manometry.
  • 24-hour ambulatory pH monitoring.

30

How does pregnancy affect GORD?

  • The foetus increases the pressure on the abdominal contents.
  • It pushes the terminal segments of the oesophagus into the thoracic cavity.
  • The last trimester of pregnancy is associated with increased abdominal pressure, and this forces gastric contents into the oesophagus.
  • The heartburn subsides in the last months of pregnancy as the uterus descends into the pelvis.

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