Oesophagus And Its Disorders

Question 1

Describe Oesophagus

Answer 1

The oesophagus is a fibromuscular tube of around 18 to 25 cm that is composed of striated
squamous epithelium.

The upper third is in fact composed of striated muscle and the lower two-
thirds are composed of smooth muscle with these two muscle types merging in between.

Question 2

Where does the Oesophagus lye

Answer 2

The
oesophagus lies posterior to the trachea and begins at the laryngopharynx specifically at the lower
border of the cricoid cartilage before extending into cervical, thoracic and abdominal parts. It also
ends at the stomach, a few centimetres from the diaphragm.

Question 3

What are the functions of the Oesophagus

Answer 3

The oesophagus transports food into
the stomach and secretes mucus whilst doing so. This protects the oesophageal tissue however,
mucus here does not provide as much protection as mucus in the stomach.

Question 4

What is the angle of the his - what is its function

Answer 4

The angle the fundus makes upwards at the stomach that starts at where the oesophagus
joins the stomach is known as the angle of His and is involved in preventing reflux into the
oesophagus.

Question 5

How is ingested food moved from mouth to stomach

Answer 5

The movement of ingested food from the mouth to the stomach through the stomach is a highly
coordinated muscular process involving the contraction and relaxation of the oesophagus.

Question 6

Food in steps from mouth ———> stomach

Answer 6

Food from
the mouth first moves into the pharynx where it encounters the upper oesophageal sphincter. This
opens and peristalsis, mediated by the vagus and splenic nerves that innervate the oesophagus, then
propels food down into the oesophagus before it reaches the lower oesophageal sphincter. This also
opens to allow the food to finally move into the stomach.

Question 7

Why does the sphincters close immediately

Answer 7

The sphincters close immediately after
food passes to prevent air from accessing the oesophagus in the case of the upper sphincter, and the
reflux of food in the case of the lower sphincter. Acid reflux can be damaging to the cells lining the
oesophagus.

Question 8

What is the upper Oesophagus sphincter composed of

Answer 8

The upper oesophageal sphincter (UOS) is composed of
striated muscle and has a musculi-cartilaginous structure. It is
usually constricted to avoid air entering the oesophagus.

Question 9

What is the lower Oesophagus sphincter composed of - key feature

Answer 9

The
lower oesophageal sphincter (LOS) is composed of smooth
muscle and acts as a flap valve. The LOS is an extremely high
pressure zone (as this is where the oesophagus merges with
the stomach) that has intrinsic and extrinsic components.

Question 10

What are the intrinsic components of the lower Oesophagul muscle - features

Answer 10

The
intrinsic component involves oesophageal muscles that are
circular and longitudinal and are under neurohormonal
influence (e.g. gastrin, Ach, VIP, NO). The intrinsic component
is also composed of clasp-like semi-circular muscle fibres on
the right hand side. These have some myogenic activity and
therefore some resting tone however, they are less responsive to acetylcholine.

Question 11

How does the clasp like semi circular muscle fibre work with the angle of his

Answer 11

The sling-like oblique
gastric (angle of His) muscle fibres on the left side work together with the clasp-like semi-circular
smooth muscle fibres to prevent regurgitation of duodenal bile, enzymes and gastric acid that can
cause irritation of the oesophageal lining, inflammation and Barrett’s oesophagus (a condition where
cells of the oesophagus grow abnormally) in extreme cases.

Question 12

What is the angle of the his also responsive to

Answer 12

These angle of His muscle fibres are also

responsive to cholinergic innervation (see the different muscle fibres on the right).

Question 13

Why is reflux most common in infants

Answer 13

The angle of His is
poorly developed in infants and the junction between the oesophagus and the stomach is in fact
vertical. This is why reflux is common in infants.

Question 14

What are the extrinsic components of the LOS

Answer 14

The extrinsic component of the LOS is the diaphragm muscle acting as the adjunctive external
sphincter (provides a pinch for the oesophagus) that also has neurohormonal influence. The crural
diaphragm encircles the LOS forming part of its external component. It forms the channel through
which the oesophagus enters the abdomen and it determines the inspiratory-spike increase in LOS
pressure.
The crural diaphragm has phrenic nerves (originate at the neck) running either side of it
that are very important for tone. Fibres of the crural diaphragm possess a pinch-like action (extrinsic
sphincter). Malfunction of the intrinsic and extrinsic components leads to GORD (gastroesophageal
reflux disease).

Question 15

DESCRIBE THE INNERVATION of the Oesophagus

Answer 15

Innervation of the oesophagus includes cholinergic and non-cholinergic innervation that especially
affect its sphincters. Acetylcholine and substance P cause contraction of the intrinsic sphincters
whilst VIP and NO initiate relaxation of intrinsic sphincters.

Question 16

How does NO work in the oesophagus

Answer 16

NO works by initiating the conversion of
GTP to cGMP that then goes on to activate PKG and allow it to activate myosin phosphatase to
dephosphorylate myosin light chain in smooth muscle undoing the work of MLCK. Both the intrinsic
and extrinsic sphincters work in conjunction to allow food to move into the stomach.

Question 17

Describe the specific innervation of the oesophagus - nerves

Answer 17

In terms of
specific innervation, the upper striated muscle of the oesophagus is supplied by somatic motor
neurons (efferent neurons initiating skeletal muscle contraction) of the vagus nerve (without
interruption) as well as splanchnic nerves. These are paired visceral nerves that carry afferent fibres
and efferent fibres of the ANS that are nearly always sympathetic fibres except in the case of the
pelvic splanchnic nerves that carry parasympathetic fibres.

Question 18

How is the lower smooth muscle of the oesophagus innervated

Answer 18

The lower smooth muscles of the
oesophagus are innervated by visceral motor neurons of the vagus nerve that have interruptions
(synapse to form pre-ganglionic and post-ganglionic nerves) and cell bodies in the oesophagus and
splanchnic plexus.

Question 19

What does the oesophagul plexus consist of

Answer 19

Other innervations of the oesophagus include the nerves encircling the
oesophagus known as the oesophageal plexus (see right some of this innervation). The DVN is the
dorsal vagal nucleus, the NA is the nucleus ambiguus and the NTS is the nucleus tractus solitarius.

The nerves involved in oesophageal innervation each work during different points of swallowing. The
information they gather from the oesophagus is integrated in the brain at the different nuclei
mentioned above. A response is then sent down these nerves to contract and relax different muscles
to allow food to move down.

Question 20

What are the successive reactions and contractions mediated by

Answer 20

These successive contractions and relaxations initiated by these nuclei
are mediated by VIP and NO in the case of relaxation, and ACh and substance P in the case of
contraction.

Question 21

What happens when food is in the mounth ( nerves )

Answer 21

When food is first in the mouth, the swallow reflex occurs. The food causes excitation of
receptors in the pharynx. An afferent stimulus then travels to the NTS that then coordinates the DVN
and NA to mediate oesophageal peristalsis and sphincter relaxation (a vagal pathway initiated by
signals not only from the pharynx, but the larynx and the stomach). Efferent impulses are also sent
back to the pharyngeal musculature and tongue. The vagal efferent fibres communicate with
myenteric neurons that mediate relaxation of the LOS. The crural diaphragm is innervated by right
and left phrenic nerves with its contraction controlled with the inspiratory centre in the brainstem
and the nucleus of the phrenic nerve.

Question 22

What triggers swallowing

Answer 22

swallowing is triggered by afferent impulses
beginning from the pharynx, specifically trigeminal, glossopharyngeal (important for taste and
sensation) and vagus nerves.

Question 23

What must occur for food to reach the pharynx

Answer 23

For food to reach the pharynx, a voluntary action must first occur that
collects material on the tongue and pushes it backwards into the pharynx.

Question 24

How is material pushed into the oesophagus

Answer 24

Efferent impulses return to pharyngeal
musculature and the tongue via trigeminal, facial and hypoglossal nerves (innervate tongue muscles).
The efferent impulses initiate waves of involuntary contractions pushing material into the
oesophagus.

Question 25

What is the order of the pharynxes that food moves into

Answer 25

Food moves from the mouth through the oropharynx and then laryngopharynx into the
oesophagus.

Question 26

What is swallowing breif

Answer 26

Swallowing is a coordinated opening and closing of the UOS and LOS in a coordinated
fashion.

Question 27

What are the 4 reflexes swallowing causes

Answer 27

Swallowing causes a number of reflex responses including the inhibition of breathing
through closure of the nasopharynx, closure of the glottis (around the vocal cords) by the epiglottis
to prevent food entering the trachea, a ring of peristaltic waves (4cm/s) behind material moving it
towards the stomach and a second wave of peristalsis moving any food remnants along.

Question 28

What happens when food passes the relaxed uos

Answer 28

When food
passes through the relaxed UOS, the UOS closes, the glottis opens and breathing resumes. The LOS
closes after material has passed through.

Question 29

What happens to food that does not reach the stomach after the first peristaltic wave

Answer 29

Some food material may not reach the stomach after the
first peristaltic waves and this material causes distension of the oesophageal lumen that stimulates
receptors in the oesophagus. This causes repeated waves of peristalsis known as secondary
peristalsis.

Question 30

Why is the secondary peristalsis also important

Answer 30

This is important because food remaining in the oesophagus can ferment and degenerate
generating lactic acid that is irritating to the lining of the oesophagus and can potentially cause
oesophageal ulcers.

Question 31

What is swallowing difficulty caused by

Answer 31

Swallowing difficulty (oropharyngeal dysphasia) is caused by the inability of the
UOS to open or discoordination of the timing between the opening of the UOS and the pharyngeal
push of the bolus of food.

Question 32

What is the pharyngeal musculature - functions

Answer 32

The pharyngeal muscles are a group of muscles that form the pharynx, which is posterior to the oral cavity, determining the shape of its lumen, and affecting its sound properties as the primary resonating cavity.

Question 33

What are the mechanisms that the oesophageal uses to prevent reflux of gastric contents

Answer 33

Reflux of gastric contents back up into the oesophagus is prevented by a number of mechanisms. The
first mechanism is the LOS closes immediately after food material has passed. The pinchcock effect of
the diaphragmatic sphincter on the LOS mediated by compression from two pillars of crus also
tightens the seal. The plug like action of the mucosal folds of the stomach (rugae) also prevents reflux
as does the abdominal pressure acting on the intra-abdominal parts of the oesophagus. The angle of
His has a valve-like effect of entry into the stomach. Distension of the stomach closes the
gastroesophageal junction in a valve-like fashion due to pressure on the intraluminal projection,
created by the angle, moving it closer to the opposite oesophageal wall (adults only). The sphincter
muscles of the UOS and LOS in general include string circular muscles that act as valves to control the
aboral movement of food.

Question 34

What is a achalasia

Answer 34

Achalasia is disorders of motility and peristalsis of

the oesophagus that includes motor function of the UOS, LOS and the body of the oesophagus.

Question 35

What is regurgitation- and causes

Answer 35

Regurgitation is a second type of disorder associated with reflux of stomach acids. This can be caused
by a weak LOS in the case of GORD. Aphagia is associated with swallowing difficulty.

Question 36

What are oesophageal spasms

Answer 36

Oesophageal
spasms are abnormal oesophageal contractions that causes food to not effectively reach the
stomach.

Question 37

What is diffuse oesophageal spasms

Answer 37

Diffuse oesophageal spasm is chest pain coming from the oesophagus that can be likened
to angina.

Question 38

What are the findings linked to achalasia

Answer 38

Achalasia is associated with different findings. These include impaired LOS relaxation (spasms),
impaired peristalsis (sphincter spasms) and delayed opening of the LOS (food fails to reach stomach
effectively) that can cause dilation of the oesophageal body with a narrow distal end (bird’s beak)
that can be viewed on an oesophagram (barium filled oesophagus).

Question 39

What does achalasia cause and its causes

Answer 39

Achalasia can cause long periods
of sporadic dysphagia as well as food regurgitation. Achalasia is caused by disorders of motility or
peristalsis of the oesophagus. This can be damage to the innervation of the oesophagus or
degenerative lesions of the vagus nerve and loss of the myenteric plexus ganglionic cells.

Question 40

What induces LOS relaxation

Answer 40

The
myenteric plexus ganglionic cells are part of important inhibitory neurons that induce LOS relaxation
and coordination of proximal to distal peristaltic contraction.

Question 41

What is throught to be the initiating factor if the disease achalasia - symptoms

Answer 41

The initiating factor of this disease is
unknown however, it is thought to be autoimmune or triggered by infection. The symptoms of
achalasia include dysphagia, vomiting and heartburn. This is a retrosternal burning sensation due to
oesophageal dysmotility, retention of acidic food as well as the generation of lactic acid from the
decomposition of this retained food.

Question 42

What can cause heartburn

Answer 42

Heartburn can also be caused by the retention of small
quantities of acid refluxed due to poor emptying of the oesophagus as well as incomplete relaxation
of the LOS.

Question 43

How can achalasia be diagnosed

Answer 43

Achalasia can be diagnosed through investigation of swallowing disorders through patient
history analysis. Swallowing difficulties generally occur as a consequence of ageing. Other ways of
diagnosis include barium radiography where the patient swallows barium. The result should be a
dilated oesophagus with beak deformity at the distal end (see right above). Oesophageal manometry
would reveal peristalsis absence.

Question 44

Why is oesophageal mankmetry perfomed on patients

Answer 44

Oesophageal manometry is performed due to a number of reasons. These include determining the
cause of cardia chest pain, evaluation of the cause of reflux of stomach acid and other contents back
up into the oesophagus (e.g. GORD) and determination of the cause of swallowing difficulty (e.g.
problems with LOS/UOS contraction and relaxation). Manometry allows for evaluation of the
strength of coordination muscle contractions as well as the relaxing function of the LOS.