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Gastro-Oesophageal Junction

This performs the function of a sphincter. Its functions are

A. to cause orderly flow of food from the oesophagus into the stomach

B. to prevent reflux of gastric contents into the oesophagus

A. The gastro-oesophageal junction is made up of 3 components :

1. Intrinsic sphincter or the lower oesophageal sphincter (LES) :

This is formed by the oesophageal smooth muscle at its lower end; the LES (unlike the rest of theoesophagus) is tonically active; however, it relaxes on swallowing. The tonic activity of the LES (in between meals) prevents reflux of gastric contents into the oesophagus.

2. Extrinsic sphincter

This is made up of skeletal muscle fibres of the crural portion of the diaphragm; these fibres surround the oesophagus (at the point where it enters the diaphragm) and exert a pinchcock-like action on the oesophagus.

3. Flap valve :

The oblique (or sling) fibres of the stomach wall create a flap valve at the gastrooesophageal junction; this valve helps to close the junction whenever the intragastric pressure rises (and thus prevents regurgitation)


B. Control of the gastro-oesophageal junction      

This is under neural control.

1. Control of internal sphincter i.e. LES

The tone of LES is under neural control from the vagus.

  1. the vagal endings which release acetylcholine à cause contraction of the internal sphincter
  2. the vagal endings (via interneurons) which release NO and VIP à cause relaxation of the internal sphincter

2. Control of external sphincter i.e. the crural portion of the diaphragm

This is under neural control from the phrenic nerves. The contraction of the crural portion of the diaphragm is coordinated with respiration and contractions of the chest and abdominal muscles.


Note: Esophageal peristalsis can be initiated by deglutition ("primary" peristalsis) or local distention ("secondary" peristalsis).


Clinical correlates


This is the name given to the condition in which food accumulates in the oesophagus; due to this, the oesophagus becomes dilated.

a. Cause :

i. the myenteric plexus of the oesophagus at the LES is deficient

ii. there is defective release of NO and VIP.

b. Because of the above,

i. there is increased resting tone in the LES

ii. the LES does not relax fully on swallowing


i. pneumatic dilation of the LES

ii. myotomy (incision of the oesophageal muscle)

iii. injection of botulinum toxin into the LES (this acts by inhibiting release of acetylcholine)

Gastro-oesophageal reflux disease (GERD)

As the name suggests, in this condition there is reflux of acid gastric contents into the oesophagus. It is due to LES incompetence (thus, it is the opposite condition to achalasia, in which there is increased tone of LES).

a. Symptoms

i. heart burn and oesophagitis

ii. there can be ulceration and stricture formation (due to scarring of the tissue) in the oesophagus

iii. in severe cases, the internal/external sphincter are weak

iv. in less severe cases, there are intermittent periods where there is less neural drive to these sphincters; the cause of this is not known.


i. H2 receptor blockers (omeprazole) : this inhibits acid secretion

ii. Fundoplication :  In this surgical procedure, a portion of the fundus of the stomach is wrapped around the lower oesophagus à thus, the oesophagus is made to lie inside a short tunnel of stomach

Pharyngo-oesophageal sphincter

1. The sphincter at the upper end of the oesophagus is called the pharyngo-oesophageal sphincter. It is formed by the tonic contraction of the crico-pharyngeus muscle. It is normally closed except during swallowing. It prevents the entry of air from the mouth into the oesophagus.  However, during the act of swallowing (e.g. drinking, eating) some air is swallowed; this is called aerophagia (‘air eating’).  Out of the air that is swallowed, some is regurgitated through the mouth during belching, some is absorbed but much of it is passed on to the colon. In the colon, some oxygen from the swallowed air is absorbed; colonic bateria act on carbohydrate and other substances to produce hydrogen, hydrogen sulphide, carbon dioxide, and methane. These latter gases are thus added to the air and passed as flatus. The smell in the flatus is mostly due to the sulphides.  Normally, the GIT has about 200 ml of gas; about 500 to 1500 ml of gas is produced/day. In some individuals, gas in the intestine can cause cramps, rumbling noises (these rumbling noises are called as borborygmi) and abdominal discomfort.        


Regarding swallowing, which is/are true?
A. it is almost impossible to swallow when the mouth is kept open
B. a normal adult swallows about 600 times per day
C. During swallowing, there is cessation of respiration (deglutition apnoea)
D. All


Total number of swallows per day:600Out of this,
along with eating/drinking:200
while awake without food:350
while sleeping:50


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