Session 3: The Anatomy of Salivation and Swallowing

Question 1

Give the different salivary glands.

Answer 1

Parotid gland
Submandibular gland
Sublingual gland
Buccal glands

Question 2

Composition of saliva.

Answer 2

Mostly water
It is hypotonic and rich in potassium and bicarbonate.
Mucins (mucous)
Amylase (serous from parotid gland mainly, ptyalin)
Lingual lipase
Immune proteins like IgA, lysozymes and lactoferrin

Question 3

What causes the degree of tonicity to vary in saliva?

Answer 3

The flow rate of the saliva through the ductal cells. If the flow rate is high the saliva won’t have enough time to transport correct ions in and out.

Question 4

Functions of saliva.

Answer 4

Speech
Hydrate food to form food bolus to alleviate swallowing.
Oral hygiene
Transmission of disease
First line of defence to pathogenic food
Solvent to dissolve flavour molecules
Begins the digestion of food

Question 5

Explain how saliva helps in oral hygiene.

Answer 5

Since saliva contains immune proteins it will help against bacteria in the mouth from feeding off the teeth.

During nights we salivate less which means deterioration can occur.

Question 6

What is xerostomia?

Answer 6

Deficiency of saliva i.e. dry mouth.

Question 7

What can xerostomia be caused by?

Answer 7

A blocked nose
Drug side-effects like from SSRIs
Radiotherapy to the head
Removal of salivary glands
Neural damage

Question 8

Neural control of the salivary glands.

Answer 8

Autonomic where the parasympathetic nervous system is the main driver to increase production (rest and digest).

Sympathetic can also stimulate secretion of small amounts of saliva but can also be a hindrance.

Question 9

Why might increased sympathetic response lead to a dry mouth instead of helping in secretion?

Answer 9

Because it can cause vasoconstriction of blood vessels to the salivary glands leading to less secretion of saliva.

Question 10

Innervation of the parotid gland.

Answer 10

Cranial nerve IX (glossopharyngeal nerve)

Question 11

Innervation of the submandibular gland.

Answer 11

Submandibular ganglion.

Question 12

Innervation of the sublingual gland.

Answer 12

Submandibular ganglion.

Question 13

Why is mumps painful?

Answer 13

Because it causes swelling of the parotid gland. This swelling is contained by the fibrous capsule of the parotid gland and cannot expand. The fibrous capsule is innervated by the trigeminal nerve and the trigeminal nerves sensory branches will pick up on the swelling and pain will be produced.

Question 14

What else might cause pain of the parotid gland?

Answer 14

Salivary stones leading to obstruction and swelling of the parotid gland.

Question 15

How can you detect stones of the parotid gland?

Answer 15

Via parotid sialography

Question 16

What are the phases of swallowing?

Answer 16

1: Oral preparatory phase
2: Pharyngeal phase
3: Oesophageal phase

Question 17

Explain the oral preparatory phase.

Answer 17

It is a voluntary mechanism where the food bolus is pushed towards the pharynx and once the bolus touches the pharyngeal, the pharyngeal phase will begin.

This phase takes anything from 0-7.4 seconds.

Question 18

Explain the pharyngeal phase.

Answer 18

It only takes about 0.2 seconds.

It is an involuntary mechanism where the soft palate seals off the nasopharynx to prevent food to go up into the nasal cavity.

The pharyngeal constrictors push the bolus downwards.

The larynx will elevate due to the suprahyoid muscles and this elevation causes the epiglottis to close. The epiglottis does not close on its own.

The vocal cords adduct to protect the airways from getting food into it. This also temporarily cease breathing.

Lastly the upper oesophageal sphincter relaxes and causes it to open. The food bolus can now go into the oesophagus.

Question 19

Explain the oesophageal phase.

Answer 19

It is involuntary and the food bolus is pushed down by peristalsis.

The upper oesophageal sphincter closes to prevent retrograde flow.

Question 20

How is it possible for a baby to eat and breathe at the same time if swallowing closes the airways?

Answer 20

Because in babies the epiglottis is much higher up and overlaps the soft palate and some of it goes into nasopharynx.

This means that air can still move and babies can still breathe.

Question 21

Briefly explain the neural control of swallowing.

Answer 21

Mechanoreceptors causes the glossopharyngeal nerve (sensory part of the pharynx) to send information to the medulla. The medulla forwards the signal to the vagus nerve which is the motor nerve of the pharynx to cause the pharyngeal constrictors to contract.

Question 22

Give examples of dysphagia.

Answer 22

Stroke causing the pharyngeal muscles to not contract.

Oesophageal carcinoma where drinking is possible but eating becomes difficult as there is a sense of something sticking in the oesophagus.

Question 23

Where in the oesophagus might food get stuck?

Answer 23

In the narrowings. There are 4 narrowings in total.

Question 24

State the narrowings of the oesophagus and explain them.

Answer 24

Junction of the oesophagus with pharynx

Where the oesophagus is crossed by the arch of the aorta

When there oesophagus is compressed by the left main bronchus

At the oesophageal hiatus where it passes through the diaphragm.

Question 25

How is gastro-oesophageal reflux prevented?

Answer 25

By the lower oesophageal sphincter and the diaphragm.

By intraabdominal oesophagus which gets compressed when intra-abdominal pressure increases.

By mucosal ‘rosette’ at cardia

By the acute angle of entry of oesophagus.