GI: Salivation and Swallowing

Question 1

What is the composition of saliva?

Answer 1

Mostly water (generally hypotonic) with potassium, bicarbonate, amylase, lipase, mucins, and immune proteins eg IgA, lysozyme

Question 2

What are the 3 pairs of salivary glands?

Answer 2

Parotid (largest), sublingual and submandibular (produces the most saliva)

Question 3

Outline the production of saliva

Answer 3

The acinar cells produce an isotonic saliva which then passes the ductal cells which are responsible for modifying the saliva so that it is hypotonic (takes out Na+ and Cl- and puts in HCO3- and K+).
There are myoepithelial cells which contract to expel the saliva into the mouth

Question 4

What happens to the composition of saliva if there is a high flow rate?

Answer 4

There is less contact time with the ductal cells for modification therefore the saliva is less hypotonic. All of the ions have less exchange EXCEPT for bicarbonate which is upregulated by high flow rates (dont need to know why)

Question 5

What are the functions of saliva?

Answer 5

• lubrication and moisture for food to create bolus
• lubricates structures to allow for phonation
• disease transmission
• oral hygiene
• initiation of digestion
• antibacterial effects
• solvent for taste molecules

Question 6

What are the causes of xerostomia (dry mouth)?

Answer 6

• mouth breathing (if nose is blocked)
• medications eg antidepressants, hypertensives etc
• chemotherapy
• smoking
• dehydration

Question 7

What is parotiditis?

Answer 7

Swelling of the parotid glands - very painful because the surrounding fascia is not very distensible
Indicates significant morbidity

Question 8

What are the phases of swallowing?

Answer 8

Oral preparatory phase
Pharyngeal phase
Oesophageal phase

Question 9

Outline the oral preparatory phase of swallowing

Answer 9

Voluntary wave of tongue which pushes bolus towards the pharynx - once bolus touches the pharyngeal wall the pharyngeal phase begins

Question 10

Outline the pharyngeal phase of swallowing

Answer 10

Involuntary. The soft palate seals off the nasopharynx and the pharyngeal constrictors push the bolus downwards. The larynx elevates which closes the epiglottis and vocal chords adduct to protect airway.
The upper oesophageal sphincter opens

Question 11

Outline the oesophageal phase of swallowing

Answer 11

Involuntary. The upper oesophageal sphincter closes and peristaltic waves carry the bolus down into the oesophagus.

Question 12

How is it possible for babies to breath and feed at the same time?

Answer 12

During breast feeding the larynx elevates and the soft palate and epiglottis interlock so the baby can breathe while swallowing.

Question 13

What areas of the oesophagus are foreign bodies most likely to get stuck?

Answer 13

Narrowed areas: junction of oesophagus with pharynx, where oesophagus is crossed by arch of aorta, where oesophagus is crossed by left main bronchus, at the oesophageal hiatus in the diaphragm.

Question 14

What are the structures than prevent gastro-oesophageal reflux?

Answer 14

• the lower oesophageal sphincter
• the oesophagus enters at an acute angle
• oesophagus goes through the diaphragm, the right crus wraps around
• oesophagus gets compressed when intra abdo pressure rises

Question 15

What are some potential causes of dysphagia?

Answer 15

May be a neurological cause eg after a stroke so unable to coordinate the swallow
May be due to a blockage of the oesophagus eg oesophageal tumour or a closely related structure compressing the oesophagus

Question 16

What are some consequences of GORD (gastro oesophageal reflux disease)?

Answer 16

• heart burn
• unpleasant taste in mouth
• barretts oesophagus
• ulceration of the oesophagus
• oesophagitis