Saliva Composition And Secretion Flashcards
Parasympathetic stimulation leads to
copious flow of watery saliva and vasodilation
Sympathetic stimulation leads to
a smaller amount of saliva secretion, rich in enzymes
Stimulants that trigger salivary stimulation include:
− Food in the mouth – reflex
− The thought of food – cephalic (e.g. Pavlov’s dog)
− Sickness/nausea – e.g. water brash as a symptom of gastroesophageal reflux
The submandibular glands secrete
seromucous saliva – 70% of total secretion
The parotid glands secrete
secrete serous saliva – 25% of total secretion
The sublingual glands secrete
mucous saliva – 5% of total secretion
Lysozyme and peroxidases
oral hygiene – antibacterial and protection of soft tissue
Calcium and bicarbonate ions →
Mineralisation of HAP and neutralisation of acids
Mucins
lubrication–protection from desiccation/or bacterial colonisation
Amylase(ptyalin)andlipase
digestion–carbohydratesandlipids
The theory is that saliva is secreted in a two-stage process:
1. Primary secretion –
2. Secondary secretion –
- acini secrete saliva (sometimes contains mucous) into the striated ducts
- the composition of saliva is altered by ductal modification
Ductal modification –
cells of the acinus have transporters on both their membranes
Sodium
o Enters through ENaC (epithelial sodium channel) in apical membrane
o Enters through sodium-hydrogen exchangers in apical and basolateral membranes
o Exits through sodium-potassium pump in basolateral membrane
Potassium
o Enters through sodium-potassium pump in basolateral membrane
o Exits through potassium-hydrogen exchanger in apical membrane
Chloride
o Enters through chloride-bicarbonate exchanger in apical membrane
o Exits through CFTR channels in apical and basolateral membranes
Bicarbonate
o Exits through chloride-bicarbonate exchanger in apical membrane
Overall:
➢ … and … are reabsorbed from the duct into cells of the …
– (They are … )
➢ … and … are secreted into the … (to a lesser extent)
– (they are …)
➢ Saliva becomes …
Sodium
Chloride
Acinus
Removed
Potassium
Bicarbonate
Lumen
Added
Hypotonic
Evidence for two-stage hypothesis:
▪ Flow rate curves
▪ Acinar/intercalated duct micropuncture
▪ Transport properties of isolated, perfused ducts
▪ Poly-lysine injection – inhibits secondary reabsorption, saliva becomes like primary fluid
As salivary … … increases, so does … of saliva:
Flow rate
Composition
There is more time available for ductal modification at … flow rates – … saliva
➢ … potassium, … sodium, bicarbonate and chloride
There is less time available for ductal modification at … flow rate – … saliva
➢ … potassium, … sodium, bicarbonate and chloride
Low
Hypotonic
More
Less
High
Primary
Less
More
Taste stimulation has a large effect on salivary composition:
• Acidic tastes cause … salivary flow
• This is due to the fact that ..
so more saliva is secreted in order to … – bicarbonate concentration …
Maximal
hydrogen ions disrupt the buffer system,
Neutralise the low ph
Increases
