S4.1 Salivation And Swallowing

Question 1

What is the composition of saliva?

Answer 1

Mostly water
Hypotonic
Amylase 
Rich in K+ and HCO3-
Mucin for lubrication

Question 2

What are the function of saliva?

Answer 2

Lubrication of food to assist swallowing
Oral hygiene against pathogens in food
Solvent for taste

Question 3

What is xerostomia?

Answer 3

Lack of salivary secretions

Get dry mouth and difficulty eating

Question 4

What are the 3 salivary glands?

Answer 4

Parotid
Sublingual
Submandibular

Question 5

How are the salivary glands under neural control and what nerve innervates each gland?

Answer 5

Autonomic - parasympathetic main driver and increases production

Parotid - glossopharyngeal nerve
Submandibular - branches of facial nerve (CT)
Sublingual - branches of facial nerve (CT)

Question 6

What are mumps?

Answer 6

Swelling over the left parotid gland

Question 7

Why could an ear infection cause dry mouth?

Answer 7

Sublingual glands supplied by a branch of facial nerve called chorda tympani, which runs through the middle ear. If ear is infected, connection to sublingual glands can be interrupted causing less saliva production.

Question 8

Describe the oral preparatory phase of swallowing

Answer 8

Voluntary, tongue pushes bolus towards pharynx until touches pharyngeal wall

Question 9

Describe the pharyngeal phase of swallowing

Answer 9

Involuntary, soft palate raises to seal off the nasopharynx, larynx elevates, epiglottis closes, vocal cords adduct, opening of upper oesophageal sphincter

Question 10

Describe the oesophageal phase of swallowing

Answer 10

Involuntary, closure of upper oesophageal sphincter, peristaltic wave carries the bolus downwards into oesophagus

Question 11

Summarise the neural control of swallowing via CN 9 and 10

Answer 11

Mechanoreceptors detect bolus
Sensory glossopharyngeal nerve sends signal to medulla
Signal synapses on vagus nerve (motor, to pharynx)
Activates pharyngeal constrictors pushing bolus inferiorly

Question 12

Which two regions does the oesophagus have narrowings?

Answer 12

Cricopharyngeal part of inferior pharyngeal constrictor muscle
Oesophageal hiatus-passes through diaphragm

Question 13

What mechanisms are in place to prevent gastro-oesophageal reflux?

Answer 13

Oesophageal sphincter
Diaphragm pinches oesophagus to prevent backflow
Mucosal rosette at cardia prevents backflow