4- Swallowing

Question 1

Describe the composition of saliva

Answer 1

Water - saliva is hypotonic 
Potassium and HCO3 (saliva is alkaline)
Mucins (help with lubrication)
Amylase (from salivary glands)
Lingual lipase (from lingual glands)

Question 2

What is xerostomia?

Answer 2

Dry mouth, reduced flow of saliva in oral cavity

Question 3

What are the salivary glands?

Answer 3

Parotid
Submandibular
Sublingual

Question 4

Describe the control of saliva content

Answer 4

Autonomic main regulator
Reduced parasympathetic input leads to dry mouth
Sympathetic stimulates a little saliva production, but also vasoconstriction

Question 5

What are the phases of swallowing and are they voluntary?

Answer 5

Oral preparatory: Voluntary
Pharyngeal: Involuntary
Oesopharyngeal: Involuntary

Question 6

What protects the nasal cavity during swallowing?

Answer 6

Elevation of the soft palate

Question 7

What protects the respiratory tract during swallowing?

Answer 7

Elevation of the larynx, which closes the epiglottis

Adduction of the vocal cords

Question 8

Which nerve is responsible for the sensory part of swallowing?

Answer 8

Glossopharyngeal (IX)

Question 9

Which nerve is responsible for innervating the muscles involved in swallowing?

Answer 9

Vagus X

Question 10

Describe the neural control of the gag reflex

Answer 10

Mechanoreceptors in wall of pharynx detect a bolus 
Glossopharygneal (IX)
Medulla 
Vagus (X) 
Pharyngeal constrictors

Question 11

What muscles are involved in the pharyngeal phase?

Answer 11

Pharyngeal constrictor muscles, move bolus from posterior aspect of oral cavity to oesophagus

Question 12

What prevents gastro-oesophageal reflux?

Answer 12

Sphincter forms from smooth muscle of distal oesophagus
Intra-abdominal oesophagus gets compressed when intra-abdominal pressure rises
Muscular rosette at cardia
Acute angle of entry of oesophagus

Question 13

What causes dysphagia?

Answer 13

Loss of neural control - eg stroke

Obstruction - eg oesophageal tumour

Question 14

Describe the pharyngeal phase of swallowing

Answer 14

Involuntary
Tongue against hard palate so food cant re-enter mouth
Soft palate elevated to close the nasopharynx
Longitudinal muscles shorten to widen the pharynx for the bolus
Epiglottis closes
Constrictor muscles move bolus
UOS relaxes

Question 15

Describe the oral phase of swallowing

Answer 15

Voluntary
Food moistened by saliva
Muscles of mastication act on temporomandibular joint, buccinator compresses cheeks against teeth
Tongue pushes against hard palate, forcing bolus to posterior oral cavity

Question 16

Describe the oesophageal phase of swallowing

Answer 16

Involuntary
Bolus enters oesophagus and is propelled downwards by striated muscle, then smooth muscle by peristalsis
LOS relaxes to allow bolus into stomach

Question 17

Since acinar cells produce isotonic fluid, how does saliva become hypotonic?

Answer 17

More ions reabsorbed than secreted from saliva
Ductal cells impermeable to water so it cant follow ions out of cell
So more ions out than water, so saliva becomes hypotonic

Question 18

What is the main neural control of saliva?

Answer 18

Parasympathetic