Session 4 - Salivation And Swallowing

Question 1

What is in the composition of saliva?

Answer 1

Mostly water
Rich in potassium and bicarbonate 
Mucins - help with lubrication
Amylase - secreted by salivary glands
Lipase - secreted by lingual glands
Immune proteins - e.g. IgA, lysozyme, lactoferrin

Question 2

What glands are responsible for salivation?

Answer 2

Parotid (mainly serous secretion)
Submandibular (serous and mucus secretion)
Sublingual (serous and mucus secretion)
Buccal (only mucus secretion)

Question 3

What are the functions of saliva?

Answer 3

Lubricate the mouth 
Lubricate food
Oral hygiene
Enzymes for digestion - amylase,lipase
Solvent for carrying taste molecules to taste buds
Defence against microorganisms- lysozyme

Question 4

Explain the role of saliva in oral hygiene.

Answer 4

1. The flow of saliva helps wash away pathogenic bacteria, as well as food particles that provide their metabolic support.
2. Saliva contains proteolytic enzymes (e.g. lysozyme) that destroy bacteria.
3. Saliva contains antibodies that can destroy bacteria.

Question 5

Is saliva production stimulated by sympathetic or parasympathetic nervous signals?

Answer 5

Parasympathetic is the main driver of saliva production.
Sympathetic stimulates secretion of small amounts of saliva, but also causes vasoconstriction which then reduces saliva production.

Question 6

What is xerostomia?

Answer 6

Xerostomia is the feeling of oral dryness , which is often associated with hypofunction of the salivary glands.

Question 7

What problems can result from xerostomia?

Answer 7

Difficulty swallowing
Difficulty speaking
Dental cavities
Mouth ulcers
Reduced taste sensation 
Increased susceptibility to oral candidiasis

Question 8

Which drugs may cause xerostomia as a side effect?

Answer 8

Antimuscarinic - they decrease saliva secretion

Question 9

Which cranial nerve supplies the parotid gland?

Answer 9

Glossopharyngeal (CN IX)

Question 10

What cranial nerve supplies the submandibular and sublingual glands?

Answer 10

Facial nerve (CN VII)

Question 11

Mumps causes swelling of what gland? Why is swelling of this gland particularly painful?

Answer 11

Mumps causes swelling of the parotid gland. The parotid glands have a tough fibrous capsule surrounding them which doesn’t stretch. This causes pain due to the build up of pressure.

Question 12

What is a sialogram?

Answer 12

A test used to diagnose blockage of a salivary gland or duct in your mouth. It involves injecting contrast through the parotid duct into the parotid gland and then using X-rays to look for any blockage.

Question 13

What are the three stages of swallowing? Which of these stages are under voluntary control?

Answer 13

Oral preparatory phase - voluntary
Pharyngeal phase - involuntary
Oesophageal phase - involuntary

Question 14

What happens in the oral preparatory phase of swallowing?

Answer 14

Bolus is pushed back towards the pharynx.

Once the bolus touches the pharyngeal wall, the pharyngeal phase begins.

Question 15

What happens in the pharyngeal phase of swallowing?

Answer 15

The soft palate seals off the nasopharynx.
Pharyngeal constrictors push the bolus downwards.
The larynx elevates, closing the epiglottis.
The vocal cords adduct (protecting the airway) and breathing temporarily ceases.
The upper oesophageal sphincter opens.

Question 16

What happens in the oesophageal phase of swallowing?

Answer 16

The upper oesophageal sphincter closes.

Peristaltic wave carries the bolus down into the oesophagus.

Question 17

Swallowing closes the airway and inhibits breathing, except for in babies. Why is it that babies are able to feed and breathe at the same time?

Answer 17

In babies the epiglottis projects up into the nasopharynx. The epiglottis directs milk laterally down into the oesophagus away from the airway.
As babies grow, their neck elongates and the epiglottis is pulled down.

Question 18

At what points does the oesophagus narrow?

Answer 18

1) Junction of the oesophagus with the pharynx
2) Where the oesophagus is crossed by the arch of the aorta
3) Where the oesophagus is compressed by the left main bronchus
4) At the oesophageal hiatus

Question 19

What sphincter prevents gastro-oesophageal reflux?

Answer 19

Lower oesophageal sphincter