OE L25 Histology of Salivary Glands

Question 1

Describe the main features of the parotid gland.

Answer 1

• Largest gland
• Secretion travels through Stensen’s duct
• Serous secretion
• Medium length striated ducts, 1 long excretory duct

Question 2

Describe the main features of the submandibular gland.

Answer 2

• Mixed secretion (serous 80% and mucous 20%)
• Secretion travels through Wharton’s duct
• Long striated ducts, 1 long main excretory duct

Question 3

Describe the main features of the sublingual gland.

Answer 3

• Mostly mucous secretion

- Short striated ducts, long branched excretory ducts

Question 4

How many minor salivary glands are there and where are they found?

Answer 4

• 500-1000 minor SGs
• Found below or within the mucous membranes of the oral cavity
• Almost everywhere except in the gingivae and anterior region of hard palate

Question 5

How are minor salivary glands categorised?

Answer 5

By location: lingual, palatal, buccal, glossopalatine, retromolar

Question 6

Where are the salivary glands derived from?

Answer 6

Derived from the epithelial layer of the stomodeum.

Question 7

Describe the 5 stages of salivary gland development.

Answer 7

1. Mesenchymal tissue underlying stomodeum instructs epithelium to form a placode, followed by branching
2. Epithelial cells form buds which become strings called epithelial cords
3. Lumen formation occurs, corresponds to later duct structures
4. Branching occurs at distal ends, these are the regions that will later develop into acini
5. Buds form at distal ends where branching occurs, have 2 distinct epithelial layers

Question 8

What signalling factors are important during the formation of epithelial cords?

Answer 8

• Growth factors secreted from mesenchymal tissue act on the epithelium (FGF, Shh, TGF-b)
• FGF7/10 from mesenchyme required for budding and acini formation

Question 9

What signalling is required for branching to occur?

Answer 9

Wnt signalling.

Question 10

What are the 2 epithelial layers of the buds (acini)?

Answer 10

• Myoepithelium: outer contracile layer

- Inner layer of serous or mucous cells

Question 11

Where can stem cells be found?

Answer 11

In the salivary ducts.

- Capacity of self-renewal and repairing injured salivary glands

Question 12

What are acini?

Answer 12

The secretory units of the salivary gland, can be serous, mucous or mixed.

Question 13

What are the lobes of salivary glands seperated by?

Answer 13

Septum.

May contain BVs and nerves to supply the parenchyma.

Question 14

What is the glandular secretory tissue called?

Answer 14

Parenchyma.

Question 15

What is the connective supporting tissue called?

Answer 15

Stroma.

Question 16

What are the 3 types of duct present in salivary glands?

Answer 16

Intercalated > striated > collecting

Question 17

How do capsules form around glands?

Answer 17

Mesenchymal condensation causes capsule formation around the major salivary glands.
This condensation is delayed for parotid glands so trapped lymph nodes are found in the gland. (Parotid tumours can metastasise via lymphatic system).

Question 18

What happens to saliva in the striated duct?

Answer 18

It becomes modified.

Sodium and chloride ions exchanged (allows us to taste salt).

Question 19

What are mixed cell glands called?

Answer 19

Serous demilunes.
Found in submandibular and sublingual glands.
Serous cell sat on top of mucous cell.

Question 20

Which cells don’t stain with H and E?

Answer 20

Mucous cells.

Question 21

Describe serous cells.

Answer 21

• Highly active, lots of ER and Golgi
• Contain secretory granules packed with amylase for starch digestion
• Stimulated by parasympathetic innervation

Question 22

What do mucous cells produce?

Answer 22

Glycoproteins called mucins (MC1 and MC2)

Question 23

Which receptor being stimulated causes serous cells to release amylase and water?

Answer 23

M3 muscarinic receptors.

Question 24

How can we detect presence of serous cells in salivary glands?

Answer 24

• Antibody coupled to peroxidase

- Peroxidase enzyme coverts substrate into brown colour seen under microscope

Question 25

What 2 staining methods can be used to stain for mucins?

Answer 25

• Toluidine blue staining

- Periodic acid staining

Question 26

When is calcium staining used?

Answer 26

Used to differentiate between serous and mucous cells in submandibular glands. Higher Ca concentration in mucous cells so stain more red.

Question 27

Describe myoepithelial cells.

Answer 27

• Contract in response to sympathetic and parasympathetic stimulation
• Squeezes acini, causes outflow of saliva
• Abundance of microfilaments for contractile force generation
• Also have a structural support role for acini

Question 28

How can we stain for myoepithelial cells?

Answer 28

• Myoepithelial cells express keratin 14
• Keratin 14 specific antibody coupled to peroxidase
• Brown staining

Question 29

Describe the intercalated duct.

Answer 29

• Smallest
• Small lumen
• Single epithelial layer
• Does not modify saliva

Question 30

Describe the striated duct.

Answer 30

• Found between intercalated and terminal ducts
• Folds create striated appearance
• Cells larger and more columnar
• Modifies saliva by removing sodium and chloride ions and replacing with bicarbonate (buffering capcity of saliva)
• Express cytokeratin 8/18, antibody coupled to peroxidase = brown staining

Question 31

Describe the terminal/excretory/collecting duct.

Answer 31

• Double layered epithelium
• Pseudo-stratified epithelium
• Large lumen

Question 32

What is a sialolith?

Answer 32

• Calcium stone
• Swollen gland, painful, inflammation
• Mainly occurs in submandibular duct due to its length and saliva being rich in calcium

Question 33

What is a mucocele?

Answer 33

• Mucous-containing cystic lesion of minor salivary gland

Question 34

What changes to salivary glands occur with age?

Answer 34

• Fibrosis: tissue becomes less elastic
• Loss of parenchyma
• Fatty degenerative changes (fat cells commonly infiltrate acini of parotid gland)
• Infiltration of lymphocytes

Xerostomia.