histology of salivary glands

Question 1

What cells is the parotid gland composed of?

Answer 1

Serous cells

Question 2

Properties of serous cells in parotid gland :

Answer 2

Watery and rich in a-amylase

• Starch digestion - digestion starts in oral cavity

Question 3

What cells are the submandibular gland composed of?

Answer 3

Both serous and mucous cells

Question 4

Ducts of the submandibular gland :

Answer 4

• Long striated ducts
• 1 long excretory duct

Question 5

What does the submandibular gland produce?

Answer 5

Growth factors important for epithelial integrity such as :

• EGF and nerve growth factor

Question 6

Common problems with the submandibular gland

Answer 6

Duct obstructions

• Prone to having sialolith formation within it

Question 7

What cells are the sublingual gland composed of?

Answer 7

Mucous cells

Question 8

What do mucous cells produce?

Answer 8

Mucous secretion

• Highly glycosylated proteins such as
  
  • Mucins which are responsible for lubrications

Question 9

Ducts of sublingual gland :

Answer 9

• Short striated ducts
• Long branched excretory ducts
  
  • Guide saliva intro oral cavity

Question 10

Steps of the development of salivary glands :

Answer 10

1. 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

2. 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

3. Lumen formation
   * Develop the ducts - ductal system forming
4. Branching Occurs at distal ends
   * Where it will develop into saliva producing acini
5. 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

Question 11

Which growth factors play a major role in inducing formation of salivary glands?

Answer 11

FGF, Shh, TGF-b and their receptors

Question 12

Where so salivary gland stem cells reside?

Answer 12

In ducts

Question 13

How are salivary gland stem cells regulated?

Answer 13

Wnt-signalling

Question 14

Organisation of major salivary gland

Answer 14

Question 15

What are acini?

Answer 15

• Secretory units made up of mucous or serous cells
• Lined with myoepithelial cells
• Embedded in connective tissue forming lobes

Question 16

What is the septum of the salivary gland?

Answer 16

• Made from connective tissue
• May contain blood vessels and nerve supply into parenchyma
  
  • Innervation to secrete saliva
• Separates lobes

Question 17

What are the lobes of the salivary gland?

Answer 17

• Contain acini
• Separated by septum

Question 18

What are the ducts of the salivary gland?

Answer 18

• 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

Question 19

Structure of lobes and lobules

Answer 19

• Two main elements:
  
  • Glandular secretory tissue:
    
    • Parenchyma
      
      • the functional tissue of an organ
  • Connective supporting tissue:
    
    • Stroma
      
      • Faintly stained - scarcely populated with cells

Question 20

types of acini

Answer 20

serous

mucous

mixed

Question 21

How are acini distinguished?

Answer 21

• Depending on secretion produced:
  
  • Parotid:Serous
    
    • (protein & water)
    • Mostly a-amylase
• Submandibular:
  
  • Mixed (80% serous & 20% mucous)
• Sublingual:
  
  • Mainly mucous (a few serous)

Question 22

Cell rolls of striated duct

Answer 22

• 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

Question 23

Contents of serous cells/acini

Answer 23

• Lots of ER and golgi apparatus
• Secretory granules (protein)
• M3 muscarinic cells found on them
  
  • Innervation cause release of amylase & water

Question 24

Role of serous cell

Answer 24

• Secretion of water & digestive enzyme such as amylase
  
  • Responsible for main volume of saliva
  • Parasympathetic innervation stimulates release: parotid

Question 25

What secondary messenger in serous acini?

Answer 25

Ca2+ and the phopholipase C system

Question 26

What is serous demilunes

Answer 26

Mucous producing gland * In a mixed serous-mucous acinus, the serous acinus forms a serous demilune around mucous acinus

Question 27

what is

Answer 27

* Serous demilunes * Mucous cells - white areas * Serous cells - dark half moon shape area

Question 28

What glands are mucous cells found in

Answer 28

Submandibular Sublingual Minor glands

Question 29

Which cells have high calcium concentrations

Answer 29

Mucous cells

Question 30

Mucous cells contain calcium - effects

Answer 30

Good source of Ca for remineralisation Sialolith formation

Question 31

What are myoepithelial cells

Answer 31

Contractile cells found surrounding acini * Squeeze acini to aid secretion of saliva Supports parenchyma

Question 32

What are intercalated ducts

Answer 32

Smallest duct Connects acini with striated duct Single epithelial layer Does not modify saliva

Question 33

Explain the recovery of Na and Cl ions in striated duct cells

Answer 33

* 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

Question 34

Structure of terminal/excretory duct

Answer 34

* Double layer of epithelial cells * Creates pseudostratified epithelium

Question 35

Answer 35

Question 36

How do sialoliths form

Answer 36

* Calcium stone * High Ca release from mucous cells * Long secretory tract * Mainly in submandibular gland * Blocks collecting duct * Painful * Inflammation

Question 37

What is mucoceles

Answer 37

* Tear to main duct of a minor gland * On lip * Mucus is excreted into the surrounding soft tissue * Needs surgical attention

Question 38

what is the role of the myoepithelial cell in saliva secretion and where are these cells found?

Answer 38

Contract to squeeze acini and secrete saliva Found surrounding acini

Question 39

* How can you distinguish the different cells found in Saliva glands? * consider: * immunohistochemistry * stains

Answer 39

Can stain for : * Mucins * Calcium * For mucous cells