OB -Salivary glands II -cellular structure and acing secretory mech L3 Flashcards
What are the constituents of salvia?
- water
- inorganic components
- organic components
Name the sequence of ducts from the acinus to the mouth.
- Acinus
- intercalated duct
- striated duct
- secretory duct
what cells are involved in the production of salvia?
cells compromising the acinus (secretory end piece)
what are the 2 types of cells that produce salvia?
- serous
- mucous
what are the shapes of salvia cells?
Pyramidal shaped cells which are polarised for function
Describe the serous acinar cells.
- Nucleus at basal part of cell
- Basophilic RER
- Granular appearance
where do serous acinar cells discharge their secretions?
into the tubular lumen via intercellular canaliculi running between the cells
Describe mucous acinar crells.
- Pale cytoplasm - mucins lost or not easily stained, so cytoplasm can appear empty in a H & E stained section
- Flattened basal nucleus
- Many large mucin granules
What are the serous demilunes that surround the mucous acinar cells?
-Cresent of serous cells
• Mucous acinus capped by serous cells
• Serous cells discharge via intercellular canaliculi between the mucous cells
What is found on acini and intercalated ducts?
myoepithelial cells
What is the function of myoepithelial cells?
• Contractile elements
• “Squeeze”acinus–may assist
secretion
• Regulate duct lumen diameter (make acinus more rigid to prevent over expansion)
why do intercalated duct have myoepithelial cells?
they are fragile and prevent from damage
Describe intercalated ducts.
- Low cuboidal cells
- Large central nucleus
- Difficult to see in routine wax sections
What is function of intercalated ducts?
Only function is to transport salvia from acinus to striated
Describe striated ducts.
• Not present in sublingual glands • Columnar shaped cells • Active modification of primary saliva • Massive basal membrane folding - suggests cells are very active (high metabolic rate)
Describe secretory ducts.
- Large lumen
- Pseudostratified columnar epithelium (layers of cells)
- Stratified near termination – merges with stratified squamous oral epithelium
what is the function of secretory ducts?
Only function is to transport salvia into the mouth
where is the formation of sn isotonic solution?
acinus
what is the name for the isotonic solution of salvia?
primary salvia
what does the Sodium potassium pump do?
pump puts sodium out the cell and brings potassium in the cell
what is stage 1 of producing primary salvia?
Increase in permeability to K+
encourages potassium to leave cell - one potassium in lumen and some outside the basal membrane
what is stage 2 of producing primary salvia?
K+ in the extracellular fluid activates a Na+ K+ Cl- co-transporter (pumped back into the cell)
What is stage 3 of producing primary salvia?
Cl- moves through the apical membrane into the lumen
what is stage 4 of producing primary salvia?
- The increased concentration of Cl- in the acinar fluid drags Na+ to balance the charge
- water then follows sodium
Name a feature of the primary salvia.
Concentrations of Na+, Cl-, HCO3- are similar to the plasma so therefore isotonic
when does the composition of the primary salvia undergo further modification?
when it passes through the ducts
Describe the conversion of isotonic solution to hypotonic solution.
- Active reabsorption of Na+ and Cl- from the lumen
- Active secretion of K+ and HCO3-into the lumen
- as the duct is impermeable to water this stays in the lumen
what is the final concentration of Na+ in the salvia at low flow rates?
very low
what is the final concentration of Na+ in the salvia at high flow rates?
High
In high flow rates what pH does the salvia reach, explain why and what role does this play.
- Striated ducts are active so bicarbonate is a bi product of active metabolism
- The harder the cell works- the more bicarbonate is produced which raises the pH
- Normal pH of salva 6.5-7 , at high flow rate it can go up to 8
- Role : High pH in salvia means more of a buffer for acid -PROTECTION
Describe the formation of organic constituents of salvia.
Most of the organic components are secreted by acinar cells
Describe the synthesis of organic components.
- Formation of peptides
- Post translational glycosylation of peptides
- Processing and packing of organic components
- Formation of condensing vacuoles
What is the main mechasnims for salvia components?
Exocytosis:
-Merocrine secretory mechanisms
(Migrate and merge with apex to discharge , cell remains the same shape)
Describe apocrine secretory mechanism.
-Higher lipid content
-Loss of part of the cell
(Secretory products - are packaged into apical portion of the cell, when stimulus occurs, whole portion breaks away and ends up in secretory fluid of the cell)
Describe holocrine secretory mechanism.
-Loss of the whole cell
whole cell is discharged into fluid - sebaceous glands only produce oil
