OCB02-2020 Flashcards
What type of gland are salivary glands?
Exocrine
What type of disease is Sjogren’s syndrome and what is its dental relevance?
Autoimmune
Loss of salivary gland function
What are possible consequences of a lack of saliva?
Tongue can become sore and red
Caries (esp in cervical areas)
Dry mouth (xerostomia)
What are the three major salivary glands called?
Parotid
Submandibular
Sublingual
Where does the Wharton duct open?
Empties at sublingual caruncles (either side of lingual frenum)
What is an alternative name for the submandibular duct?
Wharton duct
What gland drains via the Wharton duct?
Submandibular gland
Where do the ducts of Rivinus open?
Sublingual surface at sublingual folds
What is the name given to the ducts draining the sublingual gland?
Ducts of Rivinus
What gland drains via the ducts of Rivinus?
Sublingual gland
Where does the Stensen duct open?
Next to buccal surface of upper 6/7s
What is the alternative name for the parotid duct?
Stensen duct
What gland drains via the Stensen duct?
Parotid gland
Briefly describe a salivagram.
Imaging of the ductal trees and acini by injecting radiopaque dye into ducts
What is the function of salivary myoepithelial cells?
Wrap around acinus and stabilise acinus
Prevents acini cells expanding due to pressure during secretion (allows saliva to move into ducts)
What is the sequence of regions through which saliva travels from the acinus to the mouth?
Acinus = acinar cells
Intercalated duct
Striated duct
Excretory duct
Are excretory ducts located in intra- or interlobular areas?
Interlobular areas
What ducts are located intralobularly?
Intercalated duct
Striated duct
In which histological layer are minor salivary glands found?
Submucosa
How large are the secretory units of minor salivary glands?
1-2mm
What kind of saliva is produced by minor salivary glands?
Sticky/lots of mucins
Which mucosa’s minor salivary glands are most often used for diagnostic purposes?
Labial mucosa
Do minor salivary glands receive sympathetic innervation?
No
How does saliva from minor salivary glands reach the mouth?
Short ducts
Often join to secrete from one duct
What pair of salivary glands have been found in the nasopharynx?
Tubarial salivary glands
What may the function of tubarial salivary glands?
Lubrication
Innate immune function
Briefly describe the nerve-mediated reflex of salivary secretion.
Oral stimuli activate receptors and sensory nerves
Afferent pathway to nucleus tractus solitarius (brainstem)
Interneurons conduct to superior and inferior salivary nuclei or down the thoracic spinal cord
- salivary nuclei send parasympathetic efferents to major glands
- thoracic spinal cord sends sympathetic efferents to submandibular and parotid glands
What influence do higher centres have on salivary secretion?
Modulate salivary nuclei in brainstem (+/-)
Provides the only negative effect on secretion (inhibition)
Where are salivary nuclei found?
Pontine tegmentum or medulla
What oral stimuli may stimulate salivary secretion?
Gustatory/taste
Masticatory
Olfactory
Thermoreceptive
Nociceptive
Which cranial nerves are involved in the afferent pathway of salivary secretion?
Taste:
- facial nerve (C.VII)
- glossopharyngeal nerve (C.IX)
Mechano/themoreception:
- trigeminal nerve (C.V)
Which autonomic ganglion is involved in parotid gland salivary secretion?
Otic ganglion (glossopharyngeal nerve)
Which autonomic ganglion is involved in sublingual and submandibular salivary secretion?
Submandibular ganglion (lingual nerve of facial nerve)
What type of receptor is found at the glands in parasympathetic control of salivary secretion?
Muscarinic
What type of receptor is found in the ganglia in parasympathetic control of salivary secretion?
Nicotinic
Describe the role of the thoracic spinal cord in salivary secretion.
Receives input from nucleus tractus solitarius via interneurons
Sends sympathetic efferents to parotid and submandibular glands
Synapses in sympathetic ganglia in the superior cervical ganglion region
What branch(es) of autonomic innervation supply the salivary glands?
Parotid and submandibular = parasympathetic and sympathetic
Sublingual and minor = parasympathetic
What parts of the salivary glands do the autonomic nerves affect?
Myoepithelial cells = contract
Blood vessels = dilate
Duct cells = increase activity
What are the parasympathetic and sympathetic effects on salivary glands?
Parasympathetic:
- evoke most fluid and some protein secretion
- contract myoepithelial cells
- cause vasodilatation
Sympathetic: - collaborates with PS - causes protein secretion - contract myoepithelial cells (no vasoconstriction and rarely fluid secretion)
More gland atrophy will be caused by the removal of which branch of the autonomic system from salivary glands?
Parasympathetic
What part of saliva formation are parasympathetic nerves responsible for? What receptors/transmitters are used?
Na and Cl secretion (and therefore water secretion that follows)
Muscarinic ACh receptors
What part of saliva formation are sympathetic nerves mainly responsible for? What receptors/transmitters are used?
Protein secretion
β-adrenoceptors with noradrenaline
What are α-adrenoceptors responsible for in saliva formation?
Small amounts of sympathetic salt and water secretion
What happens in striated salivary ducts?
Na+ and Cl- removed but water remains
Secrete K+ into lumen
Results in hypotonic saliva
What is the role of neuropeptides in saliva formation?
Stimulate protein secretion in minor salivary glands
Give an example of a neuropeptide that may be released for saliva formation and their function.
VIP (vasointestinal peptide) = protein secretion
Substance P = fluid and electrolyte secretion
Describe what occurs in an acinar cell on stimulation (sympathetic and parasympathetic).
Parasympathetic:
- ACh binds M3 receptors to trigger Gq signalling (PLC and IP3)
- increase in intracellular calcium (from RER) causing electrolyte and fluid secretion (opening of Cl- channels)
Sympathetic:
- NA binds β-adrenoceptors to trigger Gs signalling (adenylyl cyclase and cAMP)
- protein secretion
What drugs may impact acinar cell function?
Atropine (blocks muscarinic receptor)
Propanolol (blocks β-adrenoceptors)
What is the formation of saliva mainly dependent on chemically?
Na+ gradient
What are the sodium concentrations inside and outside of acinar cells and how is this gradient maintained?
Intracellular = 10mM
Extracellular = 143mM
Na-K ATPase basolaterally (activity increases on stimulation)
How does an increase in intracellular calcium cause water movement into the lumen during saliva formation?
Causes apical Cl- channels to open so Cl- moves into lumen
Lumen becomes electronegative so Na+ follows paracellularly
Osmotic gradient formed by having NaCl in the lumen so water follows paracellularly (and partly by aquaporins)
What maintains a higher Cl- concentration in acinar cells?
Basolateral Na/K/2Cl transporter
How is saliva secretion returned to normal levels after the stimulus is removed?
Nerve signalling stops (parasympathetic)
Calcium returned to RER
Chloride channels close
Describe the protein secretion of acinar cells.
Acinar proteins are stored in granules (amylase, mucinm PRPs, statherin)
Albumin found in small amounts
Plasma cells produce IgA which are picked up by a transporter protein and carried across the cell
NA binding to β-adrenoceptors causes release of stored acinar proteind
Describe the types of saliva secreted by each major gland.
Parotid = serous (amylase and non-mucin protein)
Submandibular = mixed/seromucous
Sublingual = mucous (mucins)
What are the ionic concentrations in isotonic saliva from acini?
145mmol Na+
4mmol K+
100mmol Cl-
What are the different ionic concentrations in the saliva during unstimulated and stimulated flow rates?
Unstimulated:
- 2mmol Na+
- 25mmol K+
- 23mmol Cl-
Stimulated:
- 36mmol Na+
- 21mmol K+
- 28mmol Cl-
- 30mmol HCO3-
Which salivary flow rate produces saliva that is more hypotonic?
Unstimulated (low flow rate)
