Saliva 3 - salivary biology 1 Flashcards
What are the major pairs of salivary glands?
- parotid
- sub-mandibular
- sub-lingual
What are the key features of salivary glands?
- ducts
- acini
What are the 3 types of salivary ducts?
intercalated ducts < striated ducts < secretory ducts
Describe the path of salivary secretion
- principally starts in the acini, acini feed and produce the primary salivary secretion
- secretion travels intercalated ducts
- these ducts then feed into the striated ducts
- the striated ducts modify the saliva
- this then going through the secretory ducts, which get larger as they head towards mouth
- the secretion then goes through the larger ducts, into the papillae and out into the mouth
What is the histological structure of the acini?
pyramidal cells around a central lumen
What is the histological structure of the intercalated ducts?
very small simple cuboidal cells
What is the histological structure of the striated ducts?
massively folded basal membrane on the cells that line it, increases surface area for exchange
big cells, play a significant role in the saliva process - modify the saliva
What is the histological structure of the secretory ducts?
much larger ducts, as we get toward the mouth, the walls become increasingly stratified- multiple layers of cells lining the walls
What ducts have a role in modifying the primary secretion of saliva?
the striated ducts
Describe the pyramidal cells of the acini
wide basal margin, narrow luminal margin
polarised cells - peripheral nucleus
What do the acini produce?
primary secretion
What are the different types of acini?
- serous
- mucous
- mucous with serous demilunes
What is an example of a gland that is predominantly serous?
parotid
What is an example of a gland that is predominantly mucous?
sublingual
What is an example of a gland that is mixed (serous and mucous)?
sub-mandibular
What do serous acini cells look like?
- prominent, clear basal nucleus
- basophilic RER - manufacturing secretory cells
- granular appearance
What do mucous acini cells look like?
- pale cytoplasm - mucins lost or not easily stained
- flattened basal nucleus
- many large mucin granules
Why are the nuclei of mucous acinar cells flattened?
lots of large mucin granules - cause the nucleus to be flattened and pushed to the basal aspect of the cell
Why do mucous acinar cells look very pale in comparison to serous acinar cells?
mucous acinar cells full of mucin granules, which are either removed during processing of the section or don’t pick up the stain - cells look pale on microscope
What are mucous acinar cells with serous demilunes?
- mucous acinus capped by serous cells
- serous cells discharge via intercellular canaliculi between the mucous cells
- artifactual ?
What are myoepithelial cells?
central cell body with process sticking out, enclosing acini
Where are myoepithelial cells found?
on acini and intercalated ducts
What is the function of myoepithlial cells?
- contractile elements
- “squeeze” acinus - may assist secretion
- regulate duct lumen diameter (of the intercalated duct)
What do the cells of the intercalated ducts look like?
- low cuboidal cells
- large central nucleus
- difficult to see in routine wax sections
- in cross section, intercalated ducts look like a circle of cells around a tiny central lumen
What do intercalated ducts do?
quite passive, don’t have anything that’ll modify saliva etc., saliva produced by the acini and it passes down the intercalated ducts
- myoepithelial cells around them, can squeezed to push the saliva into the next stage (the striated ducts)
Are striated ducts present in all salivary glands?
no, not present in the sublingual glands
What do the straited ducts do?
a active modification of the primary saliva
What do the cells of the straited ducts look like?
central nucleus due to massive basal membrane folding (nucleus cannot get any more basal than it is)
In terms of cell size, compare the intercalated and striated ducts
straited ducts have very big cells aground them compared to the intercalated ducts, but still have quite a small lumen
Why is there basal membrane folding in the cells of the striated ducts?
to increase surface area for exchange with surrounding tissues, to cause changes in the saliva, lots of membrane pumps taking ions in and out of both sides of the cell (cells also have lots of mitochondria for this)
What do the secretory ducts look like?
- large lumen
- initially pseudostratified and then become stratified near termination - merges with stratified squamous oral epithelium
What is the relative size of secretory ducts, their walls and their lumen?
- secretory ducts largest in diameter, and get larger as they reach exit into mouth
- large lumen, wall relatively small despite being multilayered
