Saliva And Salivary Glands Flashcards
3 pairs of major salivary glands
Parotid
Submandibular
Sublingual
% of salivary flow by 3 pairs of major glands
80%
Minor salivary glands
Submucosa of oral mucosa - lips, cheeks, hard and soft palate, tongue
% of salivary flow from minor salivary glands
20%
2 distinct types of epithelial cells in salivary glands
Acinar cells around ducts
Structure of salivary glands
Acinar cells
Ducts- collect to form large duct entering the mouth
Equipped with channels and transporters in the apical and basolateral membranes enabling transport of fluid and electrolytes
2 types of acini
Serous acini
Mucous acini
Serous acinus structure
Dark staining nucleus in basal third
Small central duct
What do serous acini secrete
Water
Alpha amylase- starch digestion
Mucous acinus structure
Pale staining - ‘foamy’
Nucleus at base
Large central duct
What do mucous acini secrete
Mucous (water and glycoproteins)- mucin for lubrication of mucosal surfaces
Which cells are found in parotid gland
Serous acini with ducts interspersed
Which cells are found in submandibular gland
Serous and mucus acini (seromucous)
Which cells are found in sublingual gland
Serous and mucus acini (more mucus acini)
What does the intralobular duct divide into
Intercalated and striated
Intercalated ducts
Short narrow duct segments with cuboidal cells that connect acini to larger striated ducts
Striated ducts
Striped
Major site for reabsorption of NaCl
How is striated duct adapted for reabsorption
Appear striated at basal end
Basal membrane highly folded into microvilli for active transport of HCO3 against concentration gradient
Many mitochondria for ATP generation
Primary saliva
NaCl rich isotonic plasma-like fluid secreted by acini
How is the electrolyte composition of saliva modified
Duct system
Ducts secrete K+ and HCO3 - and reabsorb Na+ and Cl-
Epithelium of duct doesn’t allow any water movement so final saliva becomes hypotonic
Final saliva
Hypotonic
Parotid gland location
Superficial triangular outline between zygomatic arch, sternocleidomastoid, ramus of mandible and masseter and med pterygoid
[palpate a finger’s breadth below zygomatic arch]
Parotid duct
Stenson’s duct - crosses masseter, pierces buccinator and enters oral cavity at 7/7
Parotid gland structure
Horizontally it has a triangular outline with apex on carotid sheath
Parotid capsule very tough
Structures passing through parotid
External carotid artery and terminal branches
Retromandibular vein
Facial nerve and branches to muscles of facial expression
Submandibular glands 2 lobes
Larger superficial lobe
Smaller deep lobe in floor of mouth
What separates the 2 lobes of the submandibular glands
Mylohyoid muscle
Submandibular duct
Wharton’s duct- begins in superficial lobe, wraps round free posterior border of mylohyoid, runs along floor of mouth and empties into oral cavity at sublingual papillae
Serous demilunes
Some serous acini arranged as a crescent-shaped groups glandular cells at the bases of mucous acini in submandibular glands
Location of sublingual glands
Between mylohyoid muscle and oral mucosa of the floor of the mouth
Sublingual duct
No large duct- drains into submandibular duct and/or small ducts that pierce oral mucosa on floor of the mouth
Where are minor salivary glands located
Concentrated in the buccal labial, palatal and lingual regions
Also found at:
Superior pole of tonsils (Weber’s glands)
Tonsillar pillars
Base of tongue (von Ebner’s glands- underlying circumvallate papillae)
Weber’s glands
Superior pole of tonsils
Von Ebner’s glands
Base of the tongue
Structure of minor salivary glands
All are mucous acini (except serous glands of von Ebner)
Lack a branching network of draining ducts- each salivary unit has its own simple duct
Parasympathetic stimulation of salivary glands
Causes production of copious flow of saliva
Parasympathetic stimulation of parotid gland
Glossopharyngeal nerve
Parasympathetic stimulation of submandibular and sublingual glands
Lingual nerve
Sympathetic stimulation of salivary glands
Causes secretion of protein and glycoprotein
Functions of saliva
Lubrication for mastication, swallowing and speech
Oral hygiene- wash, immunity (antibacterial/antiviral/antifungal), buffer
Digestive enzyme- aqueous solvent necessary for taste
Maintenance of oral pH
Oral pH
7.2 [6.2-7.4]
How is oral pH maintained
Bicarbonate/carbonate buffer system for rapid neutralisation of acids
Aqueous solvent of saliva
Necessary for taste
Flow rate of saliva
0.3 - 7 ml per mintue
Daily secretion of saliva
800 - 1500 ml in adults from major and minor glands
Dysfunction of saliva is associated with
Oral pain
Infections
Increased risk of dental caries
Factors affecting composition and amount of saliva produced
Flow rate
Circadian rhythm
Type and size of gland
Duration and type of stimulus
Diet
Drugs
Age
Gender
Major contributor to oral health: lubrication
Mucous coat
Major contributor to oral health: mechanical cleaning
Flow
Major contributor to oral health: buffering salts
Neutralise acid
Major contributor to oral health: remineralisation
Ca2+ and (PO4)3-
Major contributor to oral health: defensive and digestive functions
Proteins
Saliva
Secretion of proteins and glycoproteins in a buffered electrolyte solution
Proteins in saliva
Proteomics and peptidomics of whole saliva
3652 proteins and 12,562 peptides detected to date
51% of proteins and 79% of peptides also contained in plasma
What inhibits demineralisation
Mucin
What has a function of taste in saliva
Zinc
Oral Defence provided by
Mucosa
Palatine tonsils
Salivary glands
Defence of mucosa
Physical barrier
Oral defence of palatine tonsils
Lymphocyte subsets and dendritic cells- immune surveillance and resistance to infection
Oral defence of salivary glands
Saliva washes away food particles bacteria or viruses might use for metabolic support
Immunity- salivary glands
surrounded by lymphatic system
– linked to thoracic duct and blood
Broad range of functional immune cells
Oral mucosa and glands have high blood flow rate
Which glands are continuously active
Submandibular, sublingual and minor glands
Stimulation of parotid glands
No measureable unstimulated secretion but becomes main source of saliva when stimulated
Main source of saliva when stimulated
Parotid gland
Unstimulated saliva
Dominate by SMG components
Whole saliva
Salivary gland secretions, blood, oral tissues, microorganisms and food remnants
Clinical Uses of saliva
Diagnostic/ prognostic tool
Eg for cystic fibrosis , tuberculosis
Salivary gland disease and dysfunction
Obstructive
Inflammatory
Degenerative
Drug side effects
Cancer
Xerostomia
Dry mouth
May be consequence of cystic fibrosis or Sjögren’s syndrome
Most common causes- medication and irradiation for head and neck cancers
High prevalence of caries and Candida infections
Obstruction of salivary glands
Saliva contains calcium and phosphate ions that can form salivary calculi (stones)
Most often in submandibular gland (c 80%)
Block duct at bend round mylohyoid [X] or at exit at sublingual papillae [X]
Where are salivary calculi stones most often found
Submandibular gland (80%)
What forms salivary calculi (stones)
Calcium and phosphate ions
Inflammatory disease of salivary glands
Infection secondary to blockage
Mumps (viral infection)
-Fever, malaise
-Swelling of glands
-Pain especially over parotid because capsule does not allow much enlargement
Mumps
Fever, malaise
Swelling of glands
Pain especially over parotid because capsule
does not allow much enlargement
Degenerative salivary gland disease
Complication of radiotherapy to head and neck for cancer treatment
Sjogren’s syndrome
-Mainly post-menopausal females
-Also affects lacrimal glands
-Rheumatoid arthritis may also be present
Sjögren’s syndrome
Mainly post-menopausal females
Also affects lacrimal glands
Rheumatoid arthritis may also be present
Drug side-effects on salivary glands
most common dysfunction you will encounter
About 500 prescription drugs have a sympatheticomimetic effect
-Act on NA receptors or
-inhibit parasympathetic action at ACh receptors
Sympatheticomimetic effect
Act on NA receptors or
inhibit parasympathetic action at ACh receptors
Effects of salivary gland dysfunction
If salivary output falls to < 50% of normal flow – patient experiences xerostomia (dry mouth)
Low lubrication – oral function difficult
Low (natural) oral hygiene – poor pH control
Accumulation of plaque =>Rampant dental caries, gingivitis and periodontal disease
Opportunistic infections esp. fungal infections (candida = thrush)
Low lubrication
Oral function difficult
Low natural oral hygiene
Poor pH control
Accumulation of plaque
Opportunistic infections
What classifies xerostomia (dry mouth)
Salivary output falls to <50% of normal flow
Salivary gland cancers
Rare (only about 720 cases per year)
Sublingual tumours
Almost always malignant
Adenoid Cystic Carcinoma (ACC)
ACC - relatively rare but life-threatening cancer that occurs mainly in salivary glands.
Other sites - including the breast, lacrimal gland, lung, vulva, skin.
Salivary gland ACC (SGACC) - slow growing, absence of regional metastasis,
marked tendency for perineural invasion (PI) and hematogenous dissemination.
Late recurrence or rapid progression of cases after long periods of indolent
disease are frequently seen – 30 years after initial diagnosis.
MYB oncogene
= transcriptional activator
= important roles in embryogenesis and homeostasis
= haematopoietic linkage determination
= many genes regulated by MYB linked to oncogenicity, cell proliferation, survival and differentiation
Serous secretion
Alpha amylase for starch
Mucous secretions
Mucin for lubrication of mucosal surface
Why is final saliva hypotonic
Epithelium of duct doesn’t allow any water movement
What activates parotid gland
Thought or smell
Sympathetic sensory innervation of the parotid gland
Auriculo-temporal nerve (CN V3, mandibular branch)
Sympathetic innervation of sublingual gland
Lingual nerve (branch of the facial nerve)
Parasympathetic innervation of sublingual and submandibular glands
Chorda tympani branch of facial nerve
2 lobes of submandibular glands
Larger superficial lobe and smaller deep lobe in floor of the mouth
What separates 2 lobes of submandibular gland
Mylohyoid muscle
Exosomes
Durable, cell specific lipid microvesicles
Migrate through vasculature
Reside in a number of biofluids including saliva
Could be immune response or tumour invasion promoters
Target for diagnostic tests?
What effect does a higher salivary flow rate have on the ionic composition of saliva
Less acidic as less time for HCO3- to be reabsorbed
Which immunoglobulins are found in mucus secretions?
IgA
