Oesophageal Physiology and Function

Question 1

what is distension? (in particular abdominal distension)

Answer 1

Distension refers to stretch and abdominal distension occurs when air/gas or fluids build up/accumulate in the gut causing an outward expansion beyond the normal girth of the stomach/waist.

Question 2

What is the difference between serosa and adventitia and where are they found?

Answer 2

Serosa is a smooth membrane that secretes serous fluid for lubrication and therefore it joins organs to the body wall. eg the peritoneum is the serosa that surrounds the abdo organs.

Adventia is a layer of connective tissue that binds two structures/organs to one another. eg the oesophagus is mostly covered by adventia and various other retroperitoneal organs.

Question 3

What are the three phases of swallowing?

Answer 3

Oral phase, pharyngeal phase, oesophageal phase.

Question 4

Describe the types of muscle used in each phase of swallowing?

Answer 4

Oral phase - striated muscle, voluntary
Pharygeal phase - striated muscle, involuntary (part of swallowing reflex)
Oesophageal phase - striated and smooth, involuntrary (part of swallowing reflex)

Question 5

Describe the oral phase of swallowing.

Answer 5

Oral phase - broken up into 2 phases

preparatory phase (food is chewed up and saliva works to break down solids and lubricate them)

oral transfer phase (food is pushed back to the back of the mouth into the pharynx. The tip of the tongue then pushes up onto the hard palate to close of the anterior oral cavity).

Question 6

Describe the pharyngeal phase of swallowing and what airways must be closed off in order for this to occur.

Answer 6

This is a very fast phase (

Question 7

What are the three parts of the pharynx in order from top to bottom ?

Answer 7

Nasopharynx
Oropharynx
Hypopharynx

Question 8

Describe the oesphageal phase of swallowing.

Answer 8

The oesophageal phase is where the bolus travels down the oesophagus to the stomach by peristalsis.

Question 9

Describe the structural organisation of the oesophagus.

Answer 9

The upper 1/3 of the oesophagus is striated muscle (to allow for voluntary contraction when needing to cough things up/vomiting). The lower 2/3 of the oesphagus is smooth muscle.

The mucosa of the stomach is made from stratified squamous epithelium.

Question 10

What is the difference between primary and secondary peristalsis?

Answer 10

Primary peristalsis = the contraction initiated as a result of swallowing and is a continuation of the pharyngeal contraction wave.

Secondary persitalsis = the contraction that is initiated by the bolus stretching the oesophagus and stimulating stretch receptors which initiates a reflex response therefore causing peristalsis.

Question 11

what part of the nervous system is innervating/influencing peristalsis?

Answer 11

Both branches of the autonomic nervous system as well as the enteric nervous system.

Question 12

What muscles contract during peristalsis?

Answer 12

The inner circular muscles contract inwards to shrink the diameter of the oesophagus. The outer longitudinal muscles contract length ways to shorten the length of the oesophagus.

Question 13

What is the enteric nervous system?

Answer 13

The enteric nervous system is the special nervous system of the gut. It consists of a plexus of nerves embedded in the wall of the GI tract.

The submucosal plexus (in the submucosa)
The myenteric plexus (in between the circular and longitudinal layers of muscle)

Question 14

What is the Z line?

Answer 14

Also known as the squamo-columnar junction it is the area at the distal oesophagus close to the LOS is the zone where the stratified squamous epithelium of the oesophagus changes to the columnar epithelium of the stomach.

Question 15

Are the UOS and the LOS usually contracted or relaxed?

Answer 15

Both are normally in a state of contraction but they relax soon after swallowing to allow for the bolus of food to pass through them.

However, the LOS also trasnsiently relaxes at regular intervals throughout the day (when upright) to allow for release of air from the stomach. (burping!)

Note: UOS=Skeletal muscles. LOS=Smooth muscles

Question 16

What are the three types of disorders of the oesophagus and how are they best investigated?

Answer 16

Structural disorders - endoscopy/gastroscopy (insert flexible miscroscope down into the oesophagus)

Motility disorders - barium swallow (an xray test that allows you to observe the motion of swallowing)

Functional disorders (not covered this year)

Question 17

What is GORD? (gastric-oesphageal reflux disease)

Answer 17

A disease that arises as a result of excessive amounts of gastric contents acid moving up into the oesophagus during the transient opening of the lower oesophageal sphincter.

Note: every person experiences a small amount of this reflux but it becomes pathological when symptoms from it arise.

Question 18

When does gastric-oesophageal reflux most likely to occur?

Answer 18

Directly after a big meal as this is when gastric acid accumulates in the stomach and this causes distension which pushes pressure of the LOS to open up.

Question 19

Why does GORD cause symptoms?

Answer 19

The oesophagus is lined with stratified squamous epithelium which isn’t designed to deal with the acidity of the gastric contents as unlike the stomach it does not have a mucous layer to protect it.

Symptoms occur when the mucosa of the epithelium is damaged.

Question 20

What symptoms does GORD cause?

Answer 20

Heartburn/chest discomfort - due to the sensitivty of oesophageal nerve fibres to acid

Regurgitation of food followed by a sour or bitter taste of food

Question 21

What are the immediate complications of GORD/what can it lead to?

Answer 21

Reflux oesophagitis
Peptic stricture
Barrets Oesophagus

Question 22

Explain reflux oesophagitis and its symptoms.

Answer 22

Reflux oesophagitis is the development of inflammation and ulceration and sometimes bleeding if the ulceration goes deep enough to ulcerate a blood vessel.

This is the most common cause of ulceration however it can also be caused by medication, radiation or infections such as candida/herpes.

Symptoms of oesophagitis are pain, vomitting blood (haematemesis) and dysphagia (difficulty swallowing).

Question 23

Explain peptic strictures and their symptoms.

Answer 23

Peptic strictures occur as a result of scarring and fibrosis to the oesophageal mucosa as a result of prolonged and untreated acid reflux.

Symptoms of a peptic stricture is dysphagia (difficulty swallowing) as the fibrous stricture prevents the oesophagus from being able to stretch as much as normal.

Question 24

Explain barrets oesophagus and its symptoms.

Answer 24

Barrets oesophagus occurs when prolonged acid reflux leads to a change in the epithelium lining the oesophagus from stratified squamous to columnar epithelium with goblet cells (a transition from oesophageal epithelium to gastric epithelium).

This is called intestinal metaplasia.

Question 25

What does barrets oesophagus increase the risk of, and how does this risk evolve?

Answer 25

Oesophageal adenocarcinoma (Barrets cancer).

Squmaous oesophagus - Chronic inflammation (eg by acid refluc) - barrets metaplasia (transition of cell type) - low grade dysplaisia (an early stage in the development of cancer where cells grows slowly) - high grade dysplasia (a stage in the development of cancer where cells grow quickyl) - invasive adenocarcinoma (when the cancer is at a stage where it can grow and spread beyond the lining of the oesophagus).

Question 26

What are the two types of oesophageal cancer?

Answer 26

Adenocarcinoma (related to barrets oesophagus)

Squamous cell carcinoma (related to lifestyle choices eg smoking, cholesterol).