S4) Salivation and swallowing

Question 1

Identify 5 components of saliva

Answer 1

• Mostly water
• Mucins
• Amylase
• Lingual lipase
• Immune proteins e.g. IgA, lysozyme, lactoferrin

Question 2

In terms of osmolarity, what sort of fluid is saliva?

Answer 2

Hypotonic

Question 3

Which ions are found in high concentration in saliva?

Answer 3

• Potassium ions
• Bicarbonate ions

Question 4

What is the role of mucins in saliva?

Answer 4

Mucins help with lubrication

Question 5

Where are the following enzymes secreted from:

• Amylase
• Lipase

Answer 5

• Amylase – secreted by salivary glands
• Lipase – secreted by lingual glands

Question 6

Identify 5 functions of saliva

Answer 6

• Lubricates mouth (maintains moisture)
• Begins chemical digestion
• Assists swallowing
• Allows tongue to taste food (solvent effect)
• Protects teeth

Question 7

What is xerostomia?

Answer 7

• Xerostomia is the dryness of the mouth due to a change in the composition of saliva or reduced saliva in the mouth
• It is associated with dehydration

Question 8

What are the 3 salivary glands in the body?

Answer 8

• Sublingual glands
• Submandibular glands
• Parotid glands

Question 9

Describe the location and function of the parotid gland

Answer 9

• Location: each parotid is wrapped around the mandibular ramus
• Function: secretes serous saliva through the parotid duct into the mouth

Question 10

Where are the sublingual glands located?

Answer 10

The sublingual glands lie directly under the mucous membrane covering the floor of the mouth beneath the tongue

Question 11

Where are the submandibular glands located?

Answer 11

The submandibular glands lie near the inner side of the lower jawbone, in front of the sternocleidomastoid muscle

Question 12

Describe the regulation of salivary secretion

Answer 12

• Driven by parasympathetic nervous system as it increases production of saliva
• Sympathetic nervous system also stimulates secretion of small amounts of saliva and causes vasoconstriction

Question 13

Describe the neural control of the submandibular and sublingual glands

Answer 13

Submandibular and sublingual glands are supplied by the parasympathetic nervous system through the facial nerve

Question 14

Describe the neural control of the parotid glands

Answer 14

Parotid glands are supplied by the parasympathetic nervous system through the glossopharyngeal nerve

Question 15

Which drugs might have dry mouth as a side effect?

Answer 15

Drugs which target muscarinic ACh receptors

Question 16

Identify and describe the 3 different stages in swallowing

Answer 16

• Oral preparatory phase (voluntary)
• Pharyngeal phase (involuntary)
• Oesophageal phase (involuntary)

Question 17

What occurs in the oral preparatory phase of swallowing?

Answer 17

• Bolus is pushed towards pharynx
• Once bolus touches pharyngeal wall, the next phase begins

Question 18

Describe the 5 events which occur in the pharyngeal phase of swallowing

Answer 18

⇒ Soft palate seals off nasopharynx

⇒ Pharyngeal constrictors push bolus down

⇒ Larynx elevates, closed by epiglottis

⇒ Vocal cords adduct

⇒ Upper oesophageal sphincter opens

Question 19

Why do the vocal cords adduct during the pharyngeal phase?

Answer 19

• Protect airway
• Breathing temporarily ceases

Question 20

What occurs in the oesophageal phase of swallowing?

Answer 20

• Closure of the upper oesophageal sphincter
• Peristaltic wave carries bolus downwards into oesophagus

Question 21

If swallowing closes the airway and inhibits breathing, how are long periods of breast feeding possible?

Answer 21

Infants have a higher epiglottis which allows them to breath and swallow simultaneously

Question 22

Decscribe the neural control of the gag reflex

Answer 22

Mechanoreceptors → Glossopharyngeal nerve → Medulla → Vagus nerve → Pharyngeal constrictors

Question 23

How does the gag reflex vary with age?

Answer 23

Infants have a more anterior gag reflex

Question 24

Why does dysphagia occur with a stroke?

Answer 24

Damage to the nerves and muscles which cause a stroke also involve damage to the nerves and muscles which control swallowing

Question 25

Describe the muscular changes in the oesophagus

Answer 25

• First 1/3: skeletal muscle (voluntary control)
• Middle 1/3: skeletal + smooth muscle
• Last 1/3: smooth muscle (involuntary control)

Question 26

Identify 4 anatomical mechanisms which prevent gastro-oesophageal reflux

Answer 26

• Lower oesophageal sphincter
• Diaphragm
• Mucosal ‘rosette’ at cardia
• Acute angle of entry of oesophagus