OCB02-2020 Physiology of salivary glands Flashcards
Are salivary glands exocrine or endocrine glands?
Exocrine
Where do parotid glands secrete saliva?
at the level of the upper second molar on the buccal surface
Where do submandibular and sublingual glands release saliva?
Under the surface of the tongue on either side of the frenulum
What is the major duct of the parotid gland called?
Stenson duct
What is the major duct for the submandibular gland called?
Wharton duct
What stimuli cause saliva production?
Nociception Thermoreceptive Olfactory Masticatory Gustatory
Where do the afferent and efferent nerves travel?
Via the afferent pathway to the Solitary nucleus in the medulla oblongata
Efferent nerves then travel from the ANS and thoracic spine to their effector organs
Where does the parasympathetic nerves arise?
Salivatory nuclei in the brain (ANS)
Where do the sympathetic nerves arise?
From the thoracic spine
How do the parasympathetic and sympathetic NS affect saliva?
Increase saliva production
How can salivary production be decreased?
Come from the salivary nuclei in the higher centres of the brain
Do parotid glands receive parasympathetic or sympathetic innervation?
both
Do submandibular glands receive parasympathetic or sympathetic innervation?
both
Do sublingual glands receive parasympathetic or sympathetic innervation?
only parasympathetic
Do minor salivary glands receive parasympathetic or sympathetic innervation?
only sympathetic
What cells does the autonomic nerves supply?
Acini cells
Myoepithelial cells that surround acini
Ductal cells
Control blood vessel
What are the parasympathetic effects of reflex stimuli from autonomic nerves?
Can act in isolation Stimulates most fluid secretion Evoke some protein secretion Contract my-epithelial cells Cause vasodilation as part of the secretory process Denervation causes gland atrophy
What are the sympathetic effects of reflex stimuli from autonomic nerves?
Acts synergistically with parasympathetic nerves
Causes less fluid secretion, but most protein secretion
Contracts my-epithelial cells
Denervation causes gland atrophy
How does the sympathetic NS act and on what receptors?
Via noradrenaline on B adrenergic receptors
How does the parasympathetic NS act and on what receptors?
Ach on M3 muscarinic receptors
How is saliva formed via the PaNS in stage 1?
When acetylcholine is secreted from the PaNS, it stimulates NaCl secretion which created an osmotic gradient allowing water to also enter the duct
How is saliva formed via the sympathetic NS in stage 1?
Sympathetic secretion via noradrenaline increases protein secretion into the duct therefore at this stage, the secretion is isotonic
How is saliva modified in stage 2?
As saliva moves down the duct, NaCl is removed by ductal cells, creating a hypotonic solution of saliva .
The ductal epithelium is impermeable to water, so water is retained and salt reduced
What neurotransmitters do minor glands rely on?
VIP (protein secretion) Substance P (fluid secretion)
What is the coupling of autonomic sympathetic stimulation to saliva secretion in acinar cell?
With sympathetic stimulation, noradrenaline leads to an increase in cAMP, which leads to protein secretion
What is the coupling of autonomic parasympathetic stimulation to saliva secretion in acinar cell?
Acetylcholine activates the IP3 pathway, which causes a rise in intracellular calcium which leads to electrolyte and water secretion
What is fluid and electrolyte secretion mediated by?
Calcium signalling pathway
What is protein secretion mediated by?
cAMP pathway
What drug reduces protein secretion?
Propranolol
What drug reduce fluid secretion?
Atropine
What is salivary secretion dependant on?
Sodium concentration gradient
The opening of apical chloride channels upon stimulation of acinar cells
How is saliva secreted?
There are low intracellular concentrations of sodium and high extracellular due to the Na-K pump
When acetylcholine binds to M3 receptors, it causes increase in intracellular calcium ion concentrations allowing the opening of chloride ion channels
This allows chloride to move from the intracellular space to the extracellular ductal environment
This creates an electrochemical gradient allowing sodium ions to move to the apical sides
The Na-K pump regulates intracellular ion concentration, maintaining high intracellular conc of chloride for saliva flow
When does saliva secretion stop?
Stops when acetylcholine stops occupying the muscarinic receptor, the intracellular calcium is reduced and taken back to RER
What is the most abundant Ig in saliva?
sIgA
What protein does the the parotid gland contain a lot of?
Amylase
What protein does the the sublingual gland contain a lot of?
Mucins
What are the types of secretion of all glands?
Parotid: serous
Submandibular: Serous and mucous
Sublingual: mucous
How do ductal cells modify saliva when resting?
Striated ducts remove Na+ and Cl-
K+ is secreted into the lumen
Straited ducts are impermeable to water
So saliva is hypotonic in the mouth
When are the salivary glands resting?
When it is not responding to the intake of food
How is saliva modified when salivary glands are stimulated?
There is a larger volume of saliva produced and higher rate of flow of isotonic saliva
How does the composition of saliva change when it is stimulated?
More Na+ and Cl- is present but less K+
HCO3- is also present
It is less hypotonic as less ions are removed by ductal cells, as greater volumes are secreted so less time for fluid to come into contact with ductal epithelium and be modified
