Functions of the Mouth and Oesophagus

Question 1

What is the function of the mouth?

Answer 1

Beginning of the digestive system. It mechanically breaks down food into smaller pieces easier to digest (MASTICATION). Saliva mixes with the food to begin the process of breaking it down into a form your body (small intestine) can absorb and use.

Question 2

What does mastication mean?

Answer 2

The mechanical chewing of food to increase the surface area for digestion.

Question 3

What do salivary exocrine glands secrete?

Answer 3

Amylase and lipase.

It is also a sensory function as to whether or not you should eat something.

Question 4

What do the secretory organs in the mouth secrete?

Answer 4

Mucus, fluid, and IgA, lysozymes and Lactoferrin - these have an antibacterial function.

Question 5

What are the three different secretory glands in the mouth and where are they located in the mouth?

Answer 5

1. Parotid gland - back of the mouth
2. Submandibular gland - bottom of the mouth
3. Sublingual gland - under the tongue.

Question 6

What do Acinar cells produce?

Answer 6

Secrete enzymes. Acinar cells are important for protein production, especially enzymes (e.g. salivary amylase, lipase).

Question 7

What do Ductal cells produce?

Answer 7

Secrete mucus (goblet cells). Secrete water and electrolyte. Modify the secretions.

Question 8

What volume of saliva is secreted in 24hrs?

Answer 8

1.5L

Question 9

Which gland secretes the most?

Answer 9

Submandibular - 70% of secretion. It is fairly viscous.

Question 10

Which gland secretes the most and least viscous secretion?

Answer 10

Sublingual secretes the most viscous secretion - it presents 10% of total secretion.
Parotid secretes the least viscous secretion - it is mainly water and is around 20% of the total secretion.

Question 11

Which cells produce mucus and what is the function of mucus?

Answer 11

Goblet cells produce the mucus.
Funtions:
1. Lubrication
2. Hydration - keeps the oral mucosa moist and prevents dehydration and cell death.
3. Cytoprotein - protects the oesophageal mucosa from damage.

Question 12

That is the immune function of salivary secretions?

Answer 12

IgA - are antibodies bind to pathogenic antigens.
Lactoferrin - Binds iron and is bactericidal.
Lysozymes - Attacks bacterial cell wall = cell lysis.

Question 13

How does IgA present in saliva protect against infection?

Answer 13

IgA are antibodies that bind to pathogenic antigens.
They bind and neutralise protein toxins
Block attachment of viruses to cells
Opsonise bacteria
Activate complement
Activate NK cells
Taken up by M cells in the bowel to stimulate lymphoblasts and subsequent secretion of more IgA.

Question 14

What is the salivary duct function?

Answer 14

Modify the secretion from acinar cells.
It extracts Na+ and Cl-
Secretes K+ and HCO3-.
This makes saliva hypotonic and alkaline.

Question 15

What is the reason for having alkaline saliva?

Answer 15

It protects teeth from bacterial acid.

Neutralises gastric acid that refluxes into the oesophagus.

Question 16

What is Sjogren’s syndrome?

Answer 16

It is an autoimmune attack of salivary and tear glands which results in dry mouth and eyes.

Question 17

What is Mumps virus (parotitis)

Answer 17

Prodrome of headaches and fever.
Associates with orchitits (inflammation of one or both testicles)
Inflammation of the parotic gland
MMR vaccine = prevents against the disease however increases a chance of autism development.

Question 18

What NS controls secretion?

Answer 18

The autonomic nervous system controls secretion predominantly via the parasympathetic system.

Question 19

Which cranial nerves effect salivary gland secretions?

Answer 19

VII cranial nerve (facial nerve) = Otic ganglion = affects section of the submandibular and sublingual glands.
IX cranial nerve (glossopharengeal nerve) = submandibular cervical ganglion = affects all the glands vasoconstriction, and thick mucus secretion.

Question 20

What are the stages of swallowing?

Answer 20

1. Oral preparation phase - food is manipulated in the mouth and ,masticated to reduce to a consistency that can be swallowed.
2. Oral phase - tongue propels food posteriorly until the pharyngeal swallow is triggered.
3. Pharyngeal phase - The bolus is transported through the pharynx with co-ordinated closure of the glottis via movement of the epiglottis ad cessation of breathing and relaxation of the upper oesophageal sphincter (UOS)
4. Oesophageal Phase - Oesophageal peristalsis carries the bolus from the UOS through the oesophagus to the lower oesophageal Sphincter.

Question 21

What is the anatomy of the oesophagus?

Answer 21

More than a gravity fed tube.
Smooth and striated muscle. The upper 1/3 of the gut is striated to give control, the middle is mixed and the bottom (majority of the gut) is smooth.
Complex organ (starts in the thorax ends in the abdomen). Oesophageal hiatus is the hole in the diaphragm through which the oesophagus and the vagus nerve pass.

Question 22

What is the normal structure of the GI tract and which nerves innervate it?

Answer 22

Mucosa (inner)
Inner circular
Outer longitudinal muscle.

(No serosa, no mesentery)

Auerbachs/ myenteric nerves
Meissners / Sub-muscosal nerves

Question 23

What is gastro-oesophageal reflux disease?

Answer 23

(GORD). Chronic symptoms or mucosal damage produced by the abnormal reflux in the oesophagus.

Question 24

What causes GORD?

Answer 24

Obesity
Hiatus hernia = When a part of the stomach squeezes up into the chest through and opening in the diaphragm.
Pregnancy
Zollinger Ellison syndrome - gastrin secreting tumour
Drugs that lower tone at LOS - anti cholinergic, beta agonist, benzodiazapenes.

Question 25

How does chronic heart burn causes due to GORD?

Answer 25

Your stomach is continuously making acid pH 1-2. Stomach cells are protected against the acid however the oesophagus isn’t. Therefore in GORD the acid can move up into the oesophagus causing it to burn.
If you are obese you have an increase in abdominal pressure causing GORD. In pregnancy hormones can cause GORD due to a relaxation in the sphincter.

Question 26

Dysphagia is another symptom of GORD what is this?

Answer 26

Difficulty in swallowing.

Due to inflammation or stricture and affects around 33% of patients with GORD.

Question 27

Laryngopharyngeal reflux is another symptom of GORD what is this?

Answer 27

It is characterised by a chronic cough, hoarse voice secondary to reflux into the pharynx, and a chronic earache.

Question 28

Outcome of GORD?

Answer 28

Oesophagitis (inflammation)
Stricture,
Barrett’s metaplasia,
Oesophageal adenocarcinoma. (only a 0.1-15 chance of developing adenocarcinoma from Barrett’s.

Question 29

Treatment of GORD.

Answer 29

Conservative: Weight loss, avoid food/alcohol close to bedtime, decrease alcohol, raise head of bed 20-30 cm.

Medical: Decrease acid (proton inhibitors), H2 blockers, antacids increase pH, alginates (Gaviscon) coat mucosa

Surgical: Anti reflex surgery ‘fundoplication’, repairs hiatus hernia. (Vagotomy - decreases acid production).

Question 30

Where does Barrett’s metaplasia tend to develop?

Answer 30

Near the gastro-intestinal sphincter as it is where reflux tends to occur

Question 31

Squamous cell carcinoma:

site, premalignant lesion, cause, potentially curable and 5yr survival.

Answer 31

Middle and upper part of the oesophagus,
No premalignant lesion,
Causes - alcohol, tobacco, nitrosamines.
25% curable
10% 5yr survival.

Question 32

Adenocarcinoma:

site, premalignant lesion, cause, potentially curable and 5yr survival.

Answer 32

Lower part of the oesophagus,
Premalignant lesion present
Causes - reflux
25% curable
5% 5yr survival

Question 33

What is achalasia?

Answer 33

Failure to relax.
There is a loss of myenteric plexus at the lower oesophageal sphincter = poorly relaxing LOS.
Disorder in the enteric NS.

Question 34

What are the symptoms of achalasia?

Answer 34

Dysphagia = discomfort in swallowing food and water due to poorly relaxing of the LOS
Regurgitation
Chest discomfort
Halitosis = bad breath

Question 35

Treatment of achalasia

Answer 35

Botox injection at LOS
Oesophageal dilation
Surgery - Hellers myotomy ( muscles of the cardia are cut to allow food and liquids to pass into the stomach.)