PBL notes

Question 1

Which salivary gland is the largest?

Answer 1

Parotid

Question 2

Where is it located anatomically?

Answer 2

The superficial portion of the parotid gland is located subcutaneously, in front of the external ear, and its deeper portion lies behind the ramus of the mandible

Question 3

What does the parotid duct penetrate and where does it open in the oral cavity?

Answer 3

The parotid duct (Stenson’s duct) runs across masseter and penetrates buccinators medially at a sharp angle and opens opposite upper 6/7

Question 4

Which blood vessels supply the parotid gland?

Which vessels drain the deoxygenated blood from the parotid gland?

Answer 4

Blood supply is from external carotid artery via posterior auricular and transverse facial

Venous drainage via retromandibular vein

Question 5

Which nerves supply the parotid gland?

Answer 5

Parasympathetic supply: Glossopharyngeal nerve via the otic ganglion

Question 6

Which important structures pass through the parotid gland?

Answer 6

1. Facial nerve
2. Retromandibular vein
3. External carotid artery

Question 7

Describe the constituents of saliva secreted by the parotid gland

Answer 7

Secretes stimulated saliva, amylase rich thin and watery fluid

Question 8

Describe the histology of the parotid gland

Answer 8

• Has own capsule of dense, irregular connective tissue
• Short striated ducts (simple columnar)
• Longest intercalated ducts (cuboidal) – excretory are pseudostratified
• Main gland for alpha-amylase

Question 9

What provides the sympathetic innervation of all the salivary glands?

Answer 9

Postganglionic fibres from the superior cervical ganglion travelling with the blood supply

Question 10

Where is the submandibular gland situated?

Answer 10

The submandibular gland is situated in the posterior part of the floor of the mouth, adjacent to the medial aspect of the mandible and wrapping around the posterior border of the mylohyoid muscle.

Question 11

Where does the submandibular excretory duct run and open?

Answer 11

The excretory duct (Wharton’s duct) of the submandibular gland runs forward above the mylohyoid muscle and opens into the mouth beneath the tongue at the sublingual caruncle, lateral to the lingual frenum

Question 12

Which vessels supply the submandibular gland?

Answer 12

Facial and lingual arteries

Question 13

Which nerve supplies the submandibular gland?

Answer 13

The parasympathetic nerve supply is derived mainly from the facial nerve (VII), reaching the gland through the lingual nerve and submandibular ganglion

Question 14

What seperates the deep and superficial lobes of the submandibular gland?

Answer 14

Mylohyoid muscle

Question 15

What type of saliva does the submandibular gland produce?

Answer 15

Mixed saliva

Question 16

Which gland produces the most saliva at rest?

Answer 16

Submandibular

Question 17

Which glands maintain secretion during sleep when saliva is unstimulated?

Answer 17

The submandibular and sublingual glands maintain secretion during sleep when saliva is unstimulated

Question 18

Describe the histology of the submandibular gland

Answer 18

Some mucous acinus capped with serous demilune (resembling half-moon)

Question 19

Which gland is the smallest of the paired major salivary glands?

Answer 19

Sublingual gland

Question 20

Where is the sublingual gland located?

Answer 20

The gland is located in the anterior part of the floor of the mouth between the mucosa and the mylohyoid muscle.

Question 21

How do the secretions of the sublingual gland enter the oral cavity?

Answer 21

The secretions of the sublingual gland enter the oral cavity through a series of small ducts (ducts of Rivinus) opening along the sublingual fold and often through a larger duct (Bartholin’s duct) that opens with the submandibular duct at the sublingual caruncle.

Question 22

From which vessels do the the sublingual gland receives its blood supply?

Answer 22

Sublingual and submental arteries

Question 23

Which nerve provides the parasympathetic innervation of the subligual nerve?

Answer 23

Facial nerve

Question 24

How many and where are the minor salivary glands located?

Answer 24

estimated to number between 600 and 1000, exist as small, discrete aggregates of secretory tissue present in the submucosa throughout most of the oral cavity

Question 25

What type of glands are the majority of minor glands?

Answer 25

mucous glands

Question 26

Where are the lingual serous glands located?

Answer 26

n the tongue and open into the troughs surrounding the circumvallate papillae on the dorsum of the tongue and at the foliate papillae on the sides of the tongue

Question 27

Which nerves innervate the minor glands?

Answer 27

Facial nerve

Question 28

What is the predominant interlobular ductal component?

Answer 28

Striated duct

Question 29

What connects the striated ducts to the secretory end pieces?

Answer 29

Intercalated ducts

Question 30

Where can intercellular canaliculi be found?

Answer 30

between adjacent secretory cells

Question 31

What are the 2 main types of secretory cells?

Answer 31

serous cells and mucous cells

Question 32

What do serous cells produce in general?

Answer 32

proteins and glycoproteins

Question 33

What type of side chains do serous glyocoproteins have?

Answer 33

N-linked oligosaccharide side chains

Question 34

What are the main products of mucous cells?

Answer 34

mucins which have a protein core (apomucin) that is organised into specific domains and is highly substituted with sugar residues

Question 35

What are myoepithelial cells and where are they located?

Answer 35

Myoepithelial cells are contractile cells associated with the secretory end pieces and intercalated ducts of the salivary glands.

These cells are located between the basal lamina and the secretory or duct cells and are joined to the cells by desmosomes.

Question 36

What do myoepithelial cells do?

Answer 36

The cells also help to expel the primary saliva from the end piece into the duct system.

Question 37

Where are the secretory granules stored and how are they released?

Answer 37

The secretory granules are stored in the apical cytoplasm until the cell receives an appropriate secretory stimulus.

The granule membranes fuse with the cell membrane at the apical (luminal) surface, and the contents are released into the lumen by the process of exocytosis.

Question 38

What is an effective transmitter for exocystosis in the salivary glands and how does it work?

Answer 38

• sympathetic neurotransmitter noradrenaline
• Noradrenaline binds to β- adrenergic receptors on the cell surface. Receptor activation, through guanosine triphosphate-binding proteins, stimulates adenylate cyclase to produce cAMP. Increased cAMP levels activate protein kinase A, which phosphorylates other proteins in a cascade that eventually leads to granule exocytosis.

Question 39

Release of water is regulated by which part of the autonomic nervous system?

Answer 39

Parasympathetic

Question 40

How is fluid and electrolytes released in the salivary glands?

Answer 40

1. Binding of acetylcholine to muscarinic cholinergic receptors activates phospholipase C
2. This forms inositol triphosphate which causes release of calcium from intracellular stores
3. The increased calcium concentration opens chloride channels in the apical cell membrane and potassium channels in the basolateral membrane
4. As chloride leaves the cell, it draws sodium with it through the tight junctions in the lumen to balance the electrochemical gradient
5. The osmotic gradient causes the movement of water into the lumen through aquaporin channels in the apical membrane
6. A sodium-potassium-chloride co-transporter and sodium-potassium pump in the basolateral membrane maintain the ionic and osmotic gradient during secretion

Question 41

How is saliva modified as it travels through the ducts before reaching the oral cavity?

Answer 41

1. The luminal and basolateral membranes of cells in the striated and excretory ducts have abundant transporters that function to produce a netreabsorption of Na+ and Cl– resulting in
the formation of hypotonic final saliva. 

2. The ducts also secrete K+ and HCO3− but little if any secretion or reabsorption of water occurs in the striated and excretory ducts. 

3. The final electrolyte composition of saliva varies, depending on the salivary flow rate. 

4. At high flow rates, saliva is in contact with the ductal epithelium for a shorter time, and Na+ and Cl– concentrations rise and the K+ concentration decreases.
5. At low flow rates the electrolyte concentrations change in the 
opposite direction. 

6. The HCO3− concentration, however, increases with increasing 
flow rates, reflecting the increased secretion of HCO3− by the acinar cells to drive fluid secretion. 


Question 42

Which fibres innervate the salivary glands?

Answer 42

The salivary glands are innervated by postganglionic nerve fibres of the sympathetic and parasympathetic divisions of the autonomic nervous system

Question 43

Where do the preganglionic fibres originate from?

Answer 43

Depending on the gland, preganglionic parasympathetic fibres originate in the superior or inferior salivatory nuclei in the brainstem and travel via the seventh (facial) and ninth (glossopharyngeal) cranial nerves to the submandibular and otic ganglia, where they synapse with postganglionic neurones that send their axons to the glands through the lingual and auriculotemporal nerves.

Preganglionic sympathetic nerves originate in the thoracic spinal cord, synapse with postganglionic neurones in the superior cervical ganglion, and reach the glands traveling with the arterial blood supply.