The anatomy of salivation and swallowing

Question 1

Composition of saliva

Answer 1

Mostly water

Hypotonic

Rich in potassium and bicarbonate (Ph 8)

~Mucins - lubrication
~Amylase - salivary glands
~Lingual lipase - lingual glands
~Immune proteins - IgA, lysosome, lactoferrin (sequesters iron discourage bacteria)

Question 2

Functions of saliva

Answer 2

~ keeps teeth healthy (dry mouth-> dental decay)
~ can carry disease a.k.a rabies
~ digestion
~ solvent for flavour molecules (-> taste)
~hydration
~speak (cheeks and tongue move freely)
~ lysozyme (first line of defence)

Question 3

Xerostomia

What is it, problems, causes

Answer 3

Lack of saliva
-> dental cavities, overgrowth bacteria ->
Bad breath, ulcers, rough tongue

Causes: 
Drug side effects (SSRIs, diuretics) 
Radiotherapy to head
Salivary gland removal 
Ageing

Question 4

3 pairs of salivary glands, names and location

Answer 4

Anterior -> posterior

Sublingual G - opens laterally in floor of mouth, under tongue

Submandibular G - deep part superior to mylohyoid muscle, superficial part inferior, opens medially in floor of mouth

Parotid G - duct over masseter Pearces buccinator -> open at 2nd molar opposite, in front of ears

Question 5

How are the salivary gland controlled neurally? Which nerves innervate them?

Answer 5

Primarily neural (autonomic) control - parasympathetic main driver & increases production. Sympathetic also stimulates secretion of small amounts if small stimulation BUT if lots of stimulation -> vasoconstriction e.g. when anxious

Parotid G - glossopharyngeal N 9th CN

Submandibular and sublingual supplied by facial N 7th CN

Question 6

What is MUMPs? Cause, symptoms

Answer 6

Parotitis (caused by paramyxovirus)

Painful- parotid G has a tight capsule innervated by trigeminal N 5th CN, sensitive to stretch

Symptoms: pain mastication/ salivation, headache, fever, muscle aches, weakness, fatigue, can get orchitis (testis inflation) or ovaritis (ovaries inflammation), pancreatitis

Question 7

What is parotid sialography?

Answer 7

Contrast X-ray study of parotid salivary gland

E.g. to detect a stone (pain on salivating, can pass into mouth-> grit)

Question 8

What happens in each stage of swallowing?

Answer 8

1. Oral preparatory phase (0-7.4 seconds)

Voluntary, pushes bolus -> pharynx until touches pharyngeal wall

2. Pharyngeal phase (0.2secs)
   Involuntary (reflex), soft palate seals off nasopharynx, pharyngeal constrictors push bolus down, larynx elevates And moves anteriorly closing epiglottis, vocal cords adduct & breathing stops (phrenic N switched off), opening of upper oesophageal sphincter
3. Oesophageal phase (7.6 onwards)
   Involuntary, closure upper oesophageal sphincter, peristaltic wave carries bolus into oesophagus

Question 9

What condition may cause the swallowing reflex to be impaired? What is an associate problem with this?

Answer 9

Delayed reflex in motor neurone disease -> reflux into nasal cavity -> infection (e.g. pneumonia)

May choke

Question 10

Why can babies breathe and suckle milk simultaneously?

Answer 10

V small necks so epiglottis is higher and overlaps the soft palate into nasopharynx (protection form airway) but can’t talk

Question 11

Neural control of swallowing and gag reflex

Answer 11

Mechanireceptors (detects bolus)

Glossopharyngeal N/ 9CN

Medulla

Vagus N (efferent motor response)

Pharyngeal constrictors (contract)

Gag reflux- big food/ food touches wrong place -> spasm of pharyngeal constrictors, impaired from 6months (introduce solid food) 10-15% ppl oversensitive

Question 12

Why do you have to assess swallowing in stroke patients?

Answer 12

Pharyngeal muscles may become paralysed so can choke or food -> trachea -> pneumonia

Question 13

What’s the name for a malignant tumour of the oesophagus? What is a symptom? How can it be diagnosed?

Answer 13

Oesophageal carcinoma

Feeling of solids sticking lower oesophagus

Endoscopy of lower oesophagus

Question 14

What are narrowings in the oesophagus where food can get stuck?

Answer 14

1st Junction of pharynx and oesophagus

2nd where it’s crossed by the arch of aorta

3rd crossed by left main bronchus

4th diaphragm oesophageal hiatus

Question 15

What prevents gastro-oesophageal reflux?

Answer 15

• functional sphincter from smooth muscle and part of the diaphragm distal oesophagus ‘lower oesophageal sphincter’
• intra-abdo pressure compresses oesophagus higher than pressure in intra-thoracic
• mucosal rosette at cardia
• acute angle of entry of oesophagus into stomach