Week 2 - Salivation and Swallowing, GI Embryology Flashcards
What nerve supplies the muscles of mastication?
Trigeminal nerve
How much saliva is produced each day?
1.5 litres
List some functions of saliva.
- Protects oral environment by keeping it moist and relatively alkaline
- Initiates carb digestion: salivary amylase
- Aids swallowing by helping to form a food bolus
List some effects of poor saliva production.
- Dental hygiene would suffer: dental caries and infections
- Much harder to chew and swallow food
- Harder to speak
State the components of saliva.
- Water
- Electrolytes
- HCO3-
- Bacteriostats
- Mucus
- Enzymes
Which ions are added to saliva?
K+
HCO3-
Which ions are removed from saliva?
Na+ and Cl-
State the properties of saliva that is produced in low amounts - low rate of production.
- More hypotonic
- Neutral/even slightly acidic
- Fewer enzymes compared to saliva produced in larger amounts
Saliva produced under which conditions has higher enzyme content - resting or stimulated?
Stimulated
Saliva produced under which conditions is more alkaline - resting or stimulated?
Stimulated
State three situations in which saliva production would be reduced.
- Dehydration
- Certain medications: muscarinic antagonists
- Disease: e.g. Sjogrens
At which point does the parotid duct penetrate the buccinator?
Opposite the crown of the 2nd upper molar tooth
Which cranial nerve innervates the parotid gland?
IX Cranial nerve - Glossopharyngeal nerve
Which division of the autonomic nervous system stimulates secretion of saliva rich in organic content?
Sympathetic
Which cranial nerve supplies the submandibular and sublingual glands?
Cranial nerve VII: A branch of the facial nerve called chorda tympani
John had a recent middle ear infection for which he received antibiotic treatment. Shortly afterwards, he started to feel that his mouth felt dry. What might be a possible explanation?
Loss of parasympathetic supply by chorda tympani to the submandibular and sublingual glands
Chorda tympani runs through the middle ear: infection in this area can damage this nerve
Outline the steps involved in the oral preparatory phase of swallowing.
0-7.4
- Voluntary
- Pushes bolus towards pharynx
- Once bolus touches pharyngeal wall, pharyngeal phase begins
Outline the steps involved in the pharyngeal phase of swallowing.
- 4-7.6
- Involuntary
- Soft palate seals off nasopharynx
- Pharyngeal constrictors push bolus downwards
- Larynx elevates closing epiglottis
- Vocal cords adduct, protecting airways and breathing temporarily ceases
- Opening of UOS
Outline the steps involved in the oesophageal phase of swallowing.
- 6 onwards
- Closure of the upper oesophageal sphincter
- Peristaltic wave carries bolus downwards into stomach
- Involuntary
Outline the pathway involved in the neural control of swallowing and the gag reflex.
Mechanoreceptors –> Glossopharyngeal nerve –> Medulla –> Vagus nerve –> Pharyngeal constrictors
State the anatomical narrowings present in the oesophagus.
- Junction of the pharynx and upper oesophageal sphincter
- Where it crosses the aortic arch and is crossed by the left main bronchus
- Where it penetrates the diaphragm
List three areas where presence of a tumour might make swallowing difficult.
- Oesophagus
- Oropharynx
- Cardia of the stomach
State symptoms for an upper GI malignancy (for example, oesophagus, cardiac of stomach, or oropharynx tumours).
- Dysphagia
- Weight loss
- Pain
- Malaena
- Haematemesis
Explain how a stroke (cerebrovascular accident) can make swallowing fluids more difficult than solids.
- Coordination of swallowing affected
- Fluid needs to be guided carefully into the oesophagus to avoid aspirating material into the airways
- Cerebrovascular accident can affect motor portions of the cerebral cortex/ pathways (corticobulbar tracts) that connect the cerebral cortex to the brain stem
- Damage to either - deficits in the cranial nerves that originate in the pons and medulla areas - corresponding deficit in control of the muscles of the tongue, larynx and pharynx
What is the term used for:
a. Dysphagia for solids (food sticking after swallowing)?
b. Dysphagia for liquids (initiating the swallow or choking)?
a. Oesophageal dysphagia
b. Oropharyngeal dysphagia
What technique(s) can be used to investigate oesophageal dysphagia?
- Upper GI endoscopy
2. Barium swallow
What technique(s) can be used to investigate oropharyngeal dysphagia?
- Video fluoroscopy: allows phases of swallowing to be evaluated which is particularly useful when assessing neurological disease
Define odynophagia.
Painful swallowing
State some possible causes of odynophagia.
- Oesophageal candidiasis or other causes of oesophagitis
- Peptic ulcerations
- Cancers within the oropharynx/oesophagus
What will the splanchnic mesoderm that lines the external lining of the primitive gut tube develop into?
- Smooth muscle of the viscera and blood vessels
2. Visceral peritoneum