Salivary glands Flashcards
What happens to saliva composition with age?
Saliva composition changes with age.
Time is a major factor in determining the content and composition of saliva.
This is relevant for understanding the impact of changes in saliva composition with age on oral health. Such as swallowing of food and protection against dental caries.
What are the types of salivary glands based on function?
Serous producing glands
Mucous producing glands
Mixed glands
What are the types of salivary glands anatomically?
3 pairs of major glands:
Parotid, submandibular, sublingual
How common are salivary gland tumours?
Rare but serious
What type of ducts do the major salivary glands have and what kind of saliva do they produce?
Parotid: Watery - serous saliva rich in amylase, proline rich proteins (Stenson’s duct)
Submandibular gland - More mucinous (Wharton’s duct)
Sublingual gland - Viscous saliva (Ducts of rivinus or duct of bartholin)
What kind of epithelium does the floor have?
Non-keratinized stratified squamous epithelium.
What salivary glands should be examined during examination of the oral cavity?
It is important to palpate the major salivary glands during extraoral examination
What are the types of minor salivary glands? Where are they located?
Minor salivary glands are not found within gingiva and anterior part of the hard palate.
Serous minor glands are von ebner glands below the sulci of the circumvallate and folliate papillae of the tongue.
Glands of Blandin-Nuhn located on the ventral surface of the tongue.
Palatine, glossopalatine glands are pure mucous.
Where are serous minor glands located?
Von ebner glands below the sulci of the circumvallate and folliate papillae of the tongue.
Where are glands of Blandin-Nuhn located?
Located on the ventral surface of the tongue.
What cancer is commonly seen in glands of Blandin-Nuhn?
Ventral surface of the tongue
What glands produce the saliva and how much do they contribute?
Most from submandibular (65%)
Smaller proportion from parotid gland (25%)
Lingual gland (5%)
Minor salivary glands produce the remaining (5%)
Total saliva produced per day is approximately 700 - 1200 ml per day
What is the protective function of saliva?
Lubricant (glycoproteins)
Barrier against noxious stimuli
Washing non-adherent and acellular debris
Formation of salivary pellicle (Calcium binding proteins: Tooth protection and plaque)
How does saiiva produce buffering action? Why is this useful?
Phosphate ions and bicarbonate.
Bacteria require specific pH conditions
Plaque microorganisms produce acids from sugars
What are the anti-microbial actions of saliva?
Lysozyme hydrolyzes cell walls of some bacteria
Lactoferrin binds free iron and deprives bacteria of this essential element
IgA agglutinates microorganisms
How does saliva maintain tooth integrity?
Calcium, fluoride and phosphate ions are exchanged with tooth surface
What are the tissue repair functions of saliva?
Bleeding time of oral tissues shorter than other tissues
Resulting clot less solid than normal
Remineralization
Several growth factors have been identified in saliva and contribute to healing process
How does saliva help with taste?
Solubilizing food substances that can be sensed by receptors
Solubilized food has a trophic effect on receptors
How is saliva flow regulated throughout the day?
0.5L/24h secreted mostly at day time
Saliva flow is simulated through neural pathway triggered by foods’ chewing and tasting
Almost no salivary secretion during sleep
What rate of saliva production is considered normal and what is low?
Very low UWSFR<0.1ml/min
Low 0.11 - 0.25ml/min
Normal UWSFR >0.25ml/min
How is UWSFR different between males and females?
Men produce more saliva than females
UWSFR is significantly affected by CPI, OHI-S, and BMI
How are UWSFR and risk factors correlated?
High BMI scores, moderate-to severe gingivitis and low level of oral hygiene
Where does the parotid arise embryologically? When is it first formed?
Parotid is ectoderm in origin (Forms 4-6 weeks of embryonic
life)
Where and when do the sublingual and submandibular salivary glands originate?
Sublingual-submandibular are endoderm in origin
Sublingual and minor glands develop around the 8 - 12 week mark
What do salivary glands arise from? How do they form?
Differentiation of ectomesenchyme
Development of fibrous capsule
Formation of septa that divide the gland into lobes and lobules
What are the types of tissue in salivary glands?
Glandular secretory tissue (Parenchyme)
Supportive connective tissue (stroma)
What are the types of ducts in salivary glands?
Intercalated ducts -> striated ducts -> Major collecting duct
What are the main features of serous glands?
Cytoplasm is dark and has a rough appearance with no lumen
What do mucinous cells look like
Cytoplasm looks clear
Nucleus small
Cells are in a circle bound by tight junctions with a lumen in the middle
What is the difference between primary and secondary saliva?
Primary saliva:
Serous and mucous cells.
Intercalated ducts
Modified saliva:
Striated and terminal ducts
End product is hypotonic
What controls fluid and electrolyte production in saliva?
Parasympathetic innervation
Binding of ACh to muscarinic receptors triggers opening of channels of K+, Cl-, Na+, and
Norepinephrin via alpha-adrenergic receptors triggered by substance P which activates the Ca2+
How are myoepithelial cells arranged on salivary glands?
1, 2, or 3 myoepithelial cells in each salivary and piece body.
4 to 8 processes
Desmosomes between myoepithelial cells and secretory cells
Myofilaments frequently aggregated to form dark bodies along the whole process
What is the potential issue with myoepithelial cells.
Myoepithelial cells are responsible for many cancers such as pleomorphic adenomas
What are myoepithelial cells made up of?
Intercalated ducts are more spindled-shaped and fewer processes
Ultrastructurally very similar to that of smooth muscle cells
What is the function of myoepithelial cells?
Support secretory cells
Contract and widen the diameter of secretory acini
Contraction may aid in the rupture of acinar cells of
epithelial origin
How does duct diameter get affected by the location?
As we go from the terminal ends to the major duct the duct increases in size
What do intercalated ducts look like?
They have a small diameter
They are lined by small cuboidal cells
Nucleus located in the center
Well-developed RER, Golgi apparatus, occasionally secretory granules, few microvilli
Myoepithelial cells are also present
Intercalated ducts are prominent in salivary glands having a watery secretion (such as parotid gland)
What do striated duct cells look like?
They are columnar cells
Contain a centrally located nucleus
Eosinophilic cytoplasm
Prominently striations which are indentations of the cytoplasmic membrane with many mitochondria present between the folds.
Some RER and some Golgi, short microvilli
They are basal cells
What are the structural properties of terminal excretory ducts?
Near the striated ducts they have the same
histology as the striated ducts
As the duct reaches the oral mucosa the
lining becomes stratified
Goblet cells, basal cells, clear cells.
Alter the electrolyte concentration and add
mucoid substance.
What happens to ducts as we go from terminal ends to the major duct?
Cells surrounding the lumen become more columnar
They become larger
What do the terminal excretory ducts look like?
Near the striated ducts they have the same histology as striated ducts
As the duct reaches the oral mucosa the lining becomes stratified
Goblet cells, basal cells clear cells
Alter the electrolyte concentration and add mucoid substance
oajsido
Autonomic Nervous System
Striated and terminal ducts
modification via reabsorptiona nd secretion of electrolytes
Final product is hypotonic
Rate of salivary flow
What are the features and types of inflammatory cells in salivary glands?
Fibroblasts
Inflammatory cells
Mast cells
Adipose cells
ECM
Collagen and oxytalan fibers
How is salivation controlled?
No direct inhibitory innervation
ParaSNS and SNS impulses control salivation but ParaSNS is more prevalent.
ParaSNS impulses may occur in isolation, evoke most of the fluid to be excreted, cause exocytosis, induce contraction of myoepithelial cells (sympathetic too) and cause vasodilatation.
What are the types of innervation that salivary glands receive?
2 types of innervation:
Epilemmal and hypolemmal
Beta-adrenergic receptors that induce protein secretion
L-adrenergic and cholinergic receptors that induce water and electrolyte secretion
How do hormones affect salivary gland production?
Hormones can influence the function of salivary glands. They modify salivary content but not flow.
What are the age related changes in salivary glands?
Fibrosis and fatty degenerative changes
Presence of oncocytes (eosinophilic cells containing many mitochondria)
How does heavy alcohol intake affect the parotid gland?
Alcohol causes an increase in size and fatty acid content of parotid gland
What kind of gland is the submandibular gland?
Mainly serous with some areas of mucous
What kind of gland is the sublingual gland?
Mucous mainly with serous demilunes
What are the clinical considerations of the anatomy of ducts of salivary glands?
Obstruction
Role of drugs
Systemic disorders (eg sjogren’s syndrome)
Bacterial or viral infections
Therapeutic radiation
Formation of plaque and calculus
What happens if we have obstruction and backing up of saliva?
Loss of acini replaced by fibrous connective tissue
What is sjogren’s syndrome?
Sjogren’s syndrome is an autoimmune disease which is characterized by autoimmune destruction of secretory acini which end up being replaced by fibrous tissue.
How does a mucocele/mucous retention cyst form?
Mucocele forms from trauma which can destroy the duct and so saliva can start being secreted beneath the oral mucosa
How can sialoliths be diagnosed?
Can be seen on radiograph
How can a bacterial infection affected secretions?
Pus can come out from the gland to the oral cavity
What commonly causes xerostomia?
Drugs
Radiotherapy to head and neck
Sjogren’s syndrome
Psychogenic?
HCV, and HIV disease?
What are some uncommon causes of xerostomia?
Chronic graft versus host disease
Sarcoidosis
Cystic fibrosis
Diabetes mellitus
Amyloidosis
Haemochromatosis
Wegener’s disease
Salivary gland agenesis
Triple A syndrome
Cholinergic dysautonomia
Others
What drugs lead to xerostomia?
Drugs with anti-cholinergic action: Atropine and analogues Tricyclic antidepressants Serotonin re-uptake inhibitors Anti-histamines Anti-emetics Anti-psychotics
Drugs with sympathomimetic action: Decongestants Bronchodilators Appetite suppressants Amphetamines
Other drugs: Lithium Omeprazole and others Oxbutynin Disopyramide Dideoxyinosine Didanosine Diuretics Protease inhibitors
What kind of caries does xerostomia lead to?
Cervical caries is common
Rampant caries in children
What kind of gingival disease does xerostomia lead to?
Acute gingivitis
Chronic gingivitis
What can lead to salivary gland enlargement associated xerostomia?
Sjogren’s-related inflammation
Sialadenitis
Lymphoma
Lymphadenopathy
Which parts of the mouth are minor salivary glands not found?
Minor salivary glands are not found within
gingiva and anterior part of the hard palate
What kind of saliva do minor glands produce?
Serous minor glands are the von ebner glands below the sulci of the circumvallate and folliate papillae of the tongue
Ventral tongue has the glands of Blandin-Nuhn
Palatine and glossopalatine glands are pure mucous
How does saliva assist with digestion?
It neutralizes esophageal contents
Dilutes gastric chyme
Forms food bolus
Breaks starch
How are salivary gland structures organized?
From the of the capsule surrounding and
protecting the gland pass septa that subdivide
the gland into major lobes; lobes are further
subdivided into lobules. Each lobe contains
numerous secretory units consisting of
clusters of grape-like structures (the acini)
positioned around a lumen
What do seromucus cells do? How is their structure organized for this?
They secrete polysaccharides.
they have specialized secretory organelles such as RER and prominent golgi apparatus. (Carbohydrate moieties are added) and secretory granules are released via exocytosis.
How is the secretory process different in serous cells compared to other cells?
The secretory process is continuous but cyclic
What are the important zones and structures in the serous cells?
There are complex foldings of cytoplasmic membrane
The junctional complex consists of:
Tight junctions (Zonula occludencs) -> Fusion of outer cell layer
Intermediate junction (Zonula adherens) -> Intercellular communication
Desmosomes -> Firm adhesion
What do mucous cells do? How is their structure organized for their function?
Produce, store, and secrete proteinaceous material: Smaller enzymatic component
Lots of golgi for post translational modification of saliva to create mucins.
RER is less prominent as well as having less interdigitations.
Less mitochondria
How is the macromolecular component of saliva produced?
Synthesis of protein
RER, Golgi apparatus
Ribosomes -> RER -> Postranslational modification -> Golgi apparatus -> Secretory granules
Exocytosis
Endocytosis of the granule membrane
What controls the production of fluid and electrolytes in saliva?
Parasympathetic innervation due to ACh binding to muscarinic receptors:
Activation of phospholipase -> IP3 -> Release of Ca -> Opening of channels K+, Cl-, Na+ in
Norepinephrine via alpha-adrenergic receptors results in substance P activation.
What do striated ducts do to saliva secretions?
They modify the secretion (Hypotonic solution = low sodium and chloride and high potassium)
How is ductal modification regulated?
Autonomic nervous system
Striated and terminal ducts do most of the regulation
Modification takes place via reabsorption and secretion of electrolytes
Final product is hypotonic
Rate of salivary flow is also regulated by these ducts (High: Sodium and chlorine up; potassium down)
Which saliva flow rate is more significant in correlation with symptoms of xerostomia?
Unstimulated whole saliva flow rate is more likely to correlate with symptoms of xerostomia than stimulated flow rates.
What are the oral problems associated with xerostomia?
Mucosal dryness
Liability to dental decay
Liability to gingival inflammation
Possible fungal infection
Loss of denture retention
Salivary gland infection
Taste abnormalities
What oral problems are associated with oral mucosal dryness?
Dysarthria
Dysphagia
Mucosal adhesion
Stringy saliva
What kind of gingival problems are associated with xerostomia?
Acute gingivitis
Chronic gingivitis
Desquamative gingivitis
What infections are associated with xerostomia?
Bacterial sialadenitis
Oral candidosis
What are the types of oral candidosis?
Pseudomembranous candidosis
Angular cheilitis
Denture-induced stomatitis
Median rhomboid glossitis
Erythematous candidosis
What salivary gland is most commonly affected by bacterial sialadenitis?
The parotid
How does xerostomia affect taste sensation?
Causes loss of taste or a bitter taste
How does xerostomia cause denture problems?
Causes loss of retention of upper denture
Occasional traumatic oral ulcers result
Denture-induced stomatitis
What causes xerostomia related salivary gland enlargement?
Sjogren’s-related inflammation
Sialadenitis
Lymphoma (Sjogren’s)
Lymphadenopathy (parotid)
What are some common oral features seen in patients with xerostomia?
Difficulty in mouth opening (trismus)
Telangiectasia
Oral ulceration
Mucosal white patches
Neuropathies
How are salivary gland problems investigated?
Sialography
Ultrasound
Ultrasound-guided fine-needle or
medium needle biopsy
Sialography
CT (+/-sialography)
MRI (+/-) sialography
99mTc-pertechnetate scintigraphy
Labial gland biopsy
Serology
