2) Salivation and Swallowing Flashcards
State some functions of saliva:
Lubricates mouth and food to form a bolus
Initiates digestion
Protects teeth and mucosa (antibacterial and wet)
Solvent for taste molecules
What tonicity does saliva have and how does it vary?
Hypotonic
Depends on flow rate, more isotonic at high flow
Describe the composition of saliva:
Mostly water Rich in K+ and HCO3- Mucins Amylase and Lipase Diversity of immune proteins (IgA, lysozyme, lactoferrin)
What are the mucins in saliva for?
Help with lubrication
Where are amylase and lipase secreted from respectively?
Salivary glands and lingual glands
What do duct cells do in process of modifying saliva?
Remove Na+ and Cl-
Add HCO3- and K+
How do duct cells create a hypotonic salvia?
Gaps between duct cells are tight so water can’t follow into saliva
What happens to pH of saliva at higher flow rates?
More alkaline as more HCO3- secreted into saliva
What is xerostomia?
Dryness of mouth, may be associated with change in composition of saliva or reduced salivary flow.
What are the consequences of xerostomia?
Teeth and mucosa can degrade due to dry conditions
What type of secretions come from parotid gland?
Serous secretions, 25% of saliva
What type of secretions come from sub-mandibular gland?
Both serous and mucous secretion, 70% of saliva
What type of secretions come from sublingual gland?
Secretions rich in mucus, 5% of saliva
What is salivary secretion mainly controlled by?
Autonomic nervous system
Where do the parasympathetic nerves that supply salivary glands originate?
Otic ganglion
What is the effect of PSNS on salivary gland cells?
Stimulate acinar cells to produce more saliva
Stimulate duct cells to add more HCO3-
What is the effect of SNS on salivary gland cells?
Vasoconstriction so reduced blood supply to gland, limiting salivary flow
What nerve is the parotid gland innervated by?
Cranial nerve IX
What nerve are the sublingual and submandibular glands innervated by?
Chords tympani of cranial nerve VII
Why is the innervation of sublingual and submandibular glands clinically significant?
Chords tympani runs through middle ear so infection here could damage nerve and stop parasympathetic innervation.
What effect does aldosterone have on the salivary glands?
Increases rate of ductal recovery of Na+
What is sialography?
Radiological investigation of salivary glands
Inject contrast medium, look for stones/tumours
What muscle is involved in mastication, and what’s its innervation?
Masetter muscle, trigeminal nerve
What are the 3 phases of swallowing?
Oral preparatory (voluntary), pharyngeal and oesophageal
What happens in the oral preparatory phase?
Tongue pushes bolus back onto pharynx
What happens in the pharyngeal phase?
Afferent information from pressure receptors in palate and ant. pharynx reach swallowing centre in brain stem. Causes: inhibition of breathing, raising of larynx, closing of glottis, opening of upper oesophageal sphincter.
Pharyngeal constrictors push bolus down
What happens in the oesophageal phase?
Peristaltic wave carries bolus down, co-ordinated by extrinsic nerves from swallowing centre
What types of muscle are there in the oesophagus?
Upper 1/3rd is voluntary striated (somatic)
Lower 2/3rds is smooth (PSNS)
What allows babies to swallow and breath at the same time?
Epiglottis extends up to nasopharynx
How would you investigate oesophageal dysphagia?
Barium swallow or endoscopy
How would you investigate oropharyngeal dysphagia?
Flexible endoscopy
Video fluoroscopy
What can cause difficult swallowing liquids?
Stroke or damage to brain, can’t co-ordinate muscles or epiglottis
Where are the 4 narrowings in oesophagus where food can lodge?
Junction with pharynx
Where it is crossed by arch of aorta
Compressed by left main bronchus
Oesophageal hiatus
What is odynophagia?
Pain when swallowing, usually caused by infection
