Saliva 6 - saliva constituents Flashcards
Where are minor salivary glands found?
lips, cheeks, palate, oropharynx, tongue
What type of acinar cells are in the parotid glands?
99% serous cells
What type of acinar cells are in the submandibular glands?
mixed: serous (80%) + mucous (20%)
serous demilunes often visible around the mucous acini
What type of secretion comes from the sublingual glands?
largely mucous secretions
What type of secretions come from the minor glands?
mucous secretions - except serous glands of Von Ebner
(serous glands of Von Ebner seen in association with the gustatory papillae on the tongue)
What volume of saliva is produced per day?
500-1000ml/day
What percentage of saliva is produced by the major saliva glands, and by the minor salivary glands?
> 90% from major salivary glands
<10% from minor salivary glands
What is the “unstimulated” flow rate of saliva?
0.3-0.5ml/min at rest
What is the “stimulated” flow rate of saliva?
2.0-4.0ml/min when stimulated
At rest, what glands produce the majority of the saliva?
submandibular glands (70%)
- parotid (10%)
- sublingual (10%)
- minor (10%)
When stimulated, what glands produce the majority of the saliva?
parotid glands (60%)
- submandibular (30%)
- sublingual (5%)
- minor (5%)
What kind of gustatory stimuli gives a massive increase in saliva flow?
sour stimuli
What causes the masticatory salivary reflex?
mechanoreceptors afferent neurones innervating: PDL + oral mucosa (?TMJ + ?muscles)
What is the masticatory salivary reflex?
the effect of chewing on salivary flow - mechanical stimulus stimulates salivary flow
Is the masticatory salivary reflex bilateral or ipsiateral?
predominantly ipsilateral
Does smell cause an increase in salivary flow in humans?
yes, from the submandibular glands
NOT from the parotid glands
What are the 2 types of salivary secretions?
- serous (mainly from parotid and submandibular glands)
- mucous (mainly from sublingual and minor glands)
concept of ‘whole saliva’ (mix of serous and mucous)
What are the functions of saliva?
- protects tissue
- enhances taste
- lubricates food
- speeds up oral clearance of food
- facilitates removal of carbohydrates
- neutralises organic acids
- inhibits demineralisation
- enhances remineralisation
- recycles ingested fluoride to the mouth
- discourages microbial growth
- proteins sustain enamel surface
What factors can affect salivary flow rate?
- presence of food in the mouth
-> chemical - taste
-> mechanical - chewing - smell of food (submandibular)
- time of day
- state of hydration
- drugs
- age
- size of gland
What effect does presence of food in the mouth have on salivary flow rate?
increases salivary flow rate
- chemical - taste
- mechanical - chewing
What effect does smell of food have on salivary flow rate?
increases salivary flow rate (from the submandibular glands)
What effect does time of day have on salivary flow rate?
decreases at night
What effect does state of hydration have on salivary flow rate?
decreases when dehydrated
Why can drugs have an effect on salivary flow rate?
- acting on glands
- acting on nerves
What effects can age have on salivary flow rate?
increases up to age of ~15 years then stable thereafter
unsure where old age can have an effect on its own, often drug related
What is xerostomia?
dry mouth/‘lack of saliva’
when unstimulated from <50% of normal
What can cause xerostomia?
- disease/damage
- systemic
- local (intrinsic e.g. disease in the gland, extrinsic e.g. radiotherapy)
- medications e.g. analgesics, beta-blockers, anti-histamines
- dehydration
- during sleep
What problems can be caused by xerostomia?
- increased caries
- mucosal infections (especially fungal)
- pain from oral mucosa
- difficultly chewing, swallowing, speaking
- impaired taste
How does saliva composite vary?
varies from gland to gland, and with rate of secretion
Where in the salivary glands are the electrolytes/inorganic constituents of saliva added?
added in the acinus, taken away/modified in the striated ducts
Where in the salivary glands are the formed elements/organic constituents of saliva added?
largely formed in the acini
What cations (electrolytes) are in saliva?
- sodium
- potassium
- calcium
- magnesium
What anions (electrolytes) are in saliva?
- chloride
- bicarbonate
- phosphate
- thiocyanate
- sulphate
- fluoride
- iodide
- hydroxyl
What electrolyte helps with the buffering action of saliva?
bicarbonate
Where does the bicarbonate in the saliva mainly come from?
mainly from the major glands
How does bicarbonate concentration vary with flow rate?
concentration of bicarbonate increases with flow rate, helping the saliva to buffer more and minimises risk times in sugar attacks after eating etc
What does the buffering action of saliva do?
- minimises drop in pH around teeth after consumption of sugar/acids
- minimises demineralisation of teeth
What kinds of buffers are in saliva?
- phosphate buffers
- protein buffers
What does saliva contain that helps with the mineralisation of teeth?
supersaturated with Ca^2+ and PO4^3-
In terms of mineralisation, what are high flow rates of saliva associated with?
- decrease in demineralisation of teeth
- increase in remineralisation of teeth
- increase in calculus formation
(can cause mineralisation of plaque —> calculus)
What are some of the key organic components of saliva?
- amylase
- lipase
- mucous glycoproteins (mucins)
- statherins
…
What is salivary amylase used for?
the 1st stage of carbohydrate digestion - breaks down polysaccharides (starch) -> disaccharides (maltose)
Does salivary amylase play a significant role in digestion?
may be important in the breaking down/cleansing effect of saliva
- inactivated by acid in stomach, so won’t have a big role
- possibly only for dry foods e.g. bread
- may be important in breaking down polysaccharides/starches in plaque/around teeth
Where does salivary lipase come from?
from lingual minor glands - Serous Glands of Von Ebner
What is the role of salivary lipase?
1st stage of fat digestion
- significant role??
- cleansing of tastebuds - removal of fat deposits
- remain active at gastric pH
- milk and infants
What are mucous glycoproteins (mucins)?
complex molecules
- peptide core
- oligosaccharide chains
What is the role of mucins?
- lubricate
- coat all oral soft tissues
- prevent drying
- provide barrier
- important part of “pellicle” that coats the teeth
What is the role of statherins?
- prevent precipitation of Ca^2+ and PO4^3- from saliva
- prevent calculus formation
- prevent mineralisation within salivary glands
What is the antimicrobial action of saliva?
non-specific (non-immunoglobulin)
What salivary constituents have a role in the antimicrobial actions of saliva?
- water
- mucins
- amylase
- lysozyme
- peroxidase/thiocyanate
- lactoferrin
- histatins
- cystatins
What is water’s role in the antimicrobial actions of saliva?
cleansing
What is mucins role in the antimicrobial actions of saliva?
aggregation of bacteria
What is amylase’s role in the antimicrobial actions of saliva?
interferes with bacterial adherence
What is lysozyme’s role in the antimicrobial actions of saliva?
hydrolyses some bacterial cell walls
What is peroxidase/thiocyanate’s role in the antimicrobial actions of saliva?
poisons bacteria
What is lactoferrin’s role in the antimicrobial actions of saliva?
deprives bacteria of iron
What is histatins’ role in the antimicrobial actions of saliva?
antifungal and antibacterial
What is cystatins’ role in the antimicrobial actions of saliva?
inhibit tissue-damaging bacterial enzymes
