histology of salivary glands Flashcards
What cells is the parotid gland composed of?
Serous cells
Properties of serous cells in parotid gland :
Watery and rich in a-amylase
- Starch digestion - digestion starts in oral cavity
What cells are the submandibular gland composed of?
Both serous and mucous cells
Ducts of the submandibular gland :
- Long striated ducts
- 1 long excretory duct
What does the submandibular gland produce?
Growth factors important for epithelial integrity such as :
- EGF and nerve growth factor
Common problems with the submandibular gland
Duct obstructions
- Prone to having sialolith formation within it
What cells are the sublingual gland composed of?
Mucous cells
What do mucous cells produce?
Mucous secretion
- Highly glycosylated proteins such as
- Mucins which are responsible for lubrications
Ducts of sublingual gland :
- Short striated ducts
- Long branched excretory ducts
- Guide saliva intro oral cavity
Steps of the development of salivary glands :
- Salivary glands derive from epithelial layer of stomatodeum
- Mesenchymal tissue instructs the epithelial layer to form a placode
- Rudiment is formed and branching structures to form salivary gland
- Cells invade underlying mesenchymal tissue as strings and form long cords
- Branches of the salivary glands are regulated by epithelial mesenchymal crosstalk
- Growth factors from mesenchyme play a major role in inducing formation of the salivary glands
- Lumen formation
* Develop the ducts - ductal system forming - Branching Occurs at distal ends
* Where it will develop into saliva producing acini - Buds form at distal ends
- Initially 2 layered epithelium which undergoes differentiation:
- Outer layer
- myoepithelium which is contractive
- Represents further muscle of salivary glands
- Inner layer
- serous or mucous cells which are responsible for saliva production
- Dependent on gland they sit in
Which growth factors play a major role in inducing formation of salivary glands?
FGF, Shh, TGF-b and their receptors
Where so salivary gland stem cells reside?
In ducts
How are salivary gland stem cells regulated?
Wnt-signalling
Organisation of major salivary gland
What are acini?
- Secretory units made up of mucous or serous cells
- Lined with myoepithelial cells
- Embedded in connective tissue forming lobes
What is the septum of the salivary gland?
- Made from connective tissue
- May contain blood vessels and nerve supply into parenchyma
- Innervation to secrete saliva
- Separates lobes
What are the lobes of the salivary gland?
- Contain acini
- Separated by septum
What are the ducts of the salivary gland?
- intercalated
- small ducts from the secretory acini that run into the larger striated duct.
- striated duct
- larger duct with specialised epithelial cells that remove sodium chloride from saliva
- Collecting duct
- main outlet for the final saliva
Structure of lobes and lobules
- Two main elements:
- Glandular secretory tissue:
- Parenchyma
- the functional tissue of an organ
- Parenchyma
- Connective supporting tissue:
- Stroma
- Faintly stained - scarcely populated with cells
- Stroma
- Glandular secretory tissue:
types of acini
serous
mucous
mixed
How are acini distinguished?
- Depending on secretion produced:
- Parotid:Serous
- (protein & water)
- Mostly a-amylase
- Parotid:Serous
- Submandibular:
- Mixed (80% serous & 20% mucous)
- Sublingual:
- Mainly mucous (a few serous)
Cell rolls of striated duct
- Modifies saliva
- Exchange Na and Cl ions so a hypertonic solution becomes hypotonic
- Required for us to be able to taste salty foods
- Found between intercalated and terminal ducts
Contents of serous cells/acini
- Lots of ER and golgi apparatus
- Secretory granules (protein)
- M3 muscarinic cells found on them
- Innervation cause release of amylase & water
Role of serous cell
- Secretion of water & digestive enzyme such as amylase
- Responsible for main volume of saliva
- Parasympathetic innervation stimulates release: parotid
What secondary messenger in serous acini?
Ca2+ and the phopholipase C system
What is serous demilunes
Mucous producing gland
- In a mixed serous-mucous acinus, the serous acinus forms a serous demilune around mucous acinus
what is
- Serous demilunes
- Mucous cells - white areas
- Serous cells - dark half moon shape area
What glands are mucous cells found in
Submandibular
Sublingual
Minor glands
Which cells have high calcium concentrations
Mucous cells
Mucous cells contain calcium - effects
Good source of Ca for remineralisation
Sialolith formation
What are myoepithelial cells
Contractile cells found surrounding acini
- Squeeze acini to aid secretion of saliva
Supports parenchyma
What are intercalated ducts
Smallest duct
Connects acini with striated duct
Single epithelial layer
Does not modify saliva
Explain the recovery of Na and Cl ions in striated duct cells
- To create hypotonic saliva
- Na+/K+ ATPase pumps sodium out and potassium in
- Influx of Cl and Na
- Straight forward from diagram
- Ion channels in the apical membrane face the lumen
- Bicarbonate is released into saliva and chloride removed
- Buffering capavity of saliva
- Duct cells are impermeable to water
- Na+/K+ ATPase pumps sodium out and potassium in
Structure of terminal/excretory duct
- Double layer of epithelial cells
- Creates pseudostratified epithelium
How do sialoliths form
- Calcium stone
- High Ca release from mucous cells
- Long secretory tract
- Mainly in submandibular gland
- Blocks collecting duct
- Painful
- Inflammation
What is mucoceles
- Tear to main duct of a minor gland
- On lip
- Mucus is excreted into the surrounding soft tissue
- Needs surgical attention
what is the role of the myoepithelial cell in saliva secretion and where are these cells found?
Contract to squeeze acini and secrete saliva
Found surrounding acini
- How can you distinguish the different cells found in Saliva glands?
- consider:
- immunohistochemistry
- stains
Can stain for :
- Mucins
- Calcium
- For mucous cells
