Saliva And Salivary Glands Flashcards
Functions of saliva
Lubricant for mastication, swallowing and speech
Oral hygiene - Wash
- Immunity – Antibacterial/antiviral/antifungal
- Buffer
Oral pH needs to be maintained at about pH 7.2
- bicarbonate/carbonate buffer system for rapid neutralisation of acids
Digestive enzyme
- Aqueous solvent necessary for taste
Dysfunction associated with oral pain, infections and increased risk of dental caries
Saliva
Flow rate from 0.3 to 7ml per minute
Daily secretion of 800 – 1500ml in adults from major and
minor glands.
pH ranges from 6.2 to 7.4
Serous secretion – α amylase – starch digestion
Mucus secretion – mucins for lubrication of mucosal surfaces
Parotid gland = serous
Submandibular and sublingual both mucous and serous
Minor glands mainly mucous
Factors affecting the composition and amount of saliva produced
Flow rate
Circadian rhythm
Type and size of gland
Duration and type of stimulus
Diet
Drugs
Age
Gender
Saliva- Secretion of proteins and glycoproteins in a buffered electrolyte solution
Major contributor to oral health
Lubrication – mucous coat
Mechanical cleaning – flow
Buffering salts – neutralise acid
Remineralisation – Ca 2+ and PO43-
Defensive and digestive function - proteins
Defence provided by
A)The mucosa - physical barrier
b) Palatine tonsils – lymphocyte subsets + dendritic
cells – immune surveillance and resistance to infection
c) Salivary glands – saliva washes away food particles bacteria or viruses might use for metabolic support
Immunity
Salivary glands are 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
Salivary Glands
Submandibular, sublingual and minor glands are
continuously active
Parotid – no measurable unstimulated secretion but becomes main source of saliva when stimulated (stimulation occurs before putting food into the mouth)
Unstimulated saliva is dominated by SMG components
Stimulated has composition resembling parotid secretion
Whole saliva = salivary gland secretions, blood, oral tissues,
microorganisms and food remnants
What conditions are being tested for by using saliva tests?
Cystic fibrosis, TB,
Structure of the salivary glands
Composed of two morphologically and
distinct epithelial tissue
– acinar cells around
– ducts - collect to form large
duct entering the mouth
Why is the salivary gland equipped with channels and transporters in the apical and basolateral membrane?
Enable transport of fluid and electrolytes
I.e just like any other secretory or reabsorbing epithelia
Two types of acini
Acini- a small saclike cavity in a gland, surrounded by secretory cells
Serous acini
Mucous acinus
Serous acini
Dark stainingNucleus in basal thirdSmall central duct
Secrete water + α amylase
Mucous acinus
Pale staining - ‘foamy’Nucleus at base
Large central duct
Secrete mucous (water + glycoproteins)
Intralobular ducts and main excretory duct
Intralobular ducts divided into intercalated and striated
Intercalated
short narrow duct segments with cuboidal cells that connect acini to larger striated ducts
Striated ducts
striated like a thick lawn. Major site for reabsorption of NaCl
Appear striated at basal end
Basal membrane highly folded into microvilli for active transport of HCO3 against concentration gradient
Microvilli filled with mitochondria for energy to facilitate active transport
The ducts are not just a plumbing system
Primary saliva – NaCl rich isotonic plasma-like fluid secreted by acini.
Electrolyte composition is modified in 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.
2 general pathways for protein secretion:
Slide 33
Predominant (larger arrow) leading to saliva (mucosal; across apical
membrane).
Constitutive leading mainly towards interstitium and bloodstream
(serosal; across basolateral membrane).
Entry into regulated can be saturated by overexpression of transgene
product and “overflow” can exit via constitutive into bloodstream.
3 pairs of major salivary glands
Parotid- has serous acini
Submandibular- mixed and referred to as seromucous
Sublingual- mixed but more mucous acini
Minor salivary glands
Make up 20% of salivary glands
Submucosal of oral mucosa
Lip cheeks, hard and soft palate, tongue
Parotid glands
Superficial triangular outline between Zygomatic arch, Sternocleidomastoid, Ramus of mandible +
masseter and med pterygoid
Horizontally it has a triangular outline with apex on carotid sheath
Structures passing through parotid -
External carotid artery + terminal branches
What are the parotid glands?
The parotid glands are entirely serous acini with ducts interspersed
Anatomy of submandibular glands
Two lobes separated by mylohyoid muscle
-Larger superficial lobe
-Smaller deep lobe in floor of mouth
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.
Where are the openings of the submandibular glands?
Openings of the ducts at sublingual papillae
Sublingual glands
Variable in size with mixed acini- mainly mucous
No large duct- drains into submandibular duct and/or small ducts that pierce oral mucosa on the floor of the mouth
Minor salivary gland- locations
Concentrated in the buccal labial, palatal and lingual regions.
Also found at
-superior pole of tonsils (Weber’s glands),
tonsillar pillars
-base of the tongue (von Ebner’s glands - underlying circumvallate papillae).
All minor salivary glands are mucous except serous glands of von Ebner
Minor salivary glands lack a branching network of draining ducts
- each salivary unit has own simple duct
Parasympathetic and sympathetic stimulation
Stimulation of parasympathetic nerves causes the production of a copious flow of saliva while sympathetic stimulation selectively causes secretion of protein and glycoprotein
Salivary gland disease and dysfunction
Obstructive
Inflammatory
Degenerative
Drug side effects
Cancer
Obstruction
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]
Inflammatory
Infection secondary to blockage
Mumps (viral infection)
-Fever, malaise
-Swelling of glands
-Pain especially over parotid because capsule
does not allow much enlargement
Degenerative
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
Drug side effects
The most common dysfunction
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)
