Salivary Biology Flashcards
Unit structure of salivary gland
- Secretory ducts
- Striated ducts
- Intercalated ducts
- Acini
Where is the first saliva (primary) initially produced ?
Acini
Intercalated duct
Take the saliva from the acini and feed it into the striated duct. Don’t do much to the saliva.
Striated duct
Folded basal membrane - hence name.
Folding of the cell increases the surface area (for exchange). Play a significant role in modification of the saliva.
Secretory duct
Much larger. Moving towards the mouth, the wall of the ducts becomes stratified (multiple layers of cells).
Structure of acini
- Pyramidal cells with a central lumen.
- Polarised cells - peripheral nucleus.
- Different acini produce different saliva types
What is this type of cell?
Serous acinar cell (prominent nucleus, basophilic RER, granular, DARK staining)
What kind of Salivary cell is this?
Mucous acinar cell (pale cytoplasm, not easily stained, flattened nucleus, many large mucin granules)
What kind of salivary cell is this?
Mucous acinus & serous demilune ( artefactual? Mucous acini capped by serous cells)
Myoepithelial cells
On acini and intercalated ducts:
- Contractile elements
- “squeeze” secrection
structure of intercalated ducts
Low cuboidal cells, large central nucleus, difficult to see in routine wax section
Structure of striated ducts
- Not present in sublingual glands
- Active modification of primary salivary
- Central nucleus due to massive basal membrane folding.
Structure of secretory (collecting) ducts
- Large lumen
- Pseudostratified
- Stratified near termination - merges with stratified squamous oral epithelium.
Consituents of saliva
Water, electrolytes, organic components
Primary acinar secretion
- Cell at rest; sodium outside is high, potassium inside is high.
- Activated by nerve; increases permeability of cell to potassium.
- Lots of potassium now outside the cell; this activates the movement of sodium, potassium and chloride into the cell.
- This increases basal exchange of sodium to move outside the cell, and potassium into the cell.
- Potassium and chloride then flows out.
- Shift in charge (sodium is attracted - by chloride - between the cells to move into saliva).
- Water is then drawn into the saliva through osmotic gradient.
What is the primary acinar secrection like?
Ionic concentrations similar to that of plasma.
Concentrations unaffected by flow rate.
Will undergo modification in the ductal system.
Ductal modification
- Conversion from isotonic to a hypotonic solution
- Resorption of Na+ and Cl-
- Secretion of HCO3- and K+
- Dependent upon flow rate.
Striated ducts at rest
Impermeable to water (active transport happening)
Striated ducts cell activated
Increase in potassium inside the cell and decrease of Na+
Striated ducts activates: compensatory movements to and from the lumen
As the saliva flows through the striated ducts, there is an increase in potassium concentration and a decrease in sodium and chloride concentration.
Striated duct cell activated: exchanger
Active pump is activated, Bicarbonate and chloride.
Adds bicarbonate to secretion and removes chlorides.
Bicarbonate buffers pH changes.
Striated duct; flow rate low
Much time for resorption of Na+ (very low Na+ in saliva)
Striated duct; high flow rate
Less time for resorption of Na+, less reduction (Na+) in saliva
Striated duct; high gland activity
Increased HCO3- bicarbonate in saliva
Organic components
Secreted by the acinar cells
Sympathetic saliva
Fight or flight, dilation, heart rate up etc
Saliva is = viscous low volume secrection (“dry mouth”)
Parasympathetic salvia
Rest and digest, heart decreases, elimination of faeces.
Frey’s syndrome
- sometimes seen post- parotid surgery
- damage to auriculotemporal nerve
- Regeneration of damaged nerves (nerves mixed and misdirected)
- salivary stimulation activated sweat glands.
= gustatory sweating.
Control of salivation
- Gustily afferents (sour etc)
- Mechanoreceptive afferent (PDL fibres etc)
