Salivary glands: anatomy and function

Question 1

What are the functions of saliva?

Answer 1

• Lubricant for mastication, swallowing and speech
• Oral hygiene: wash, immunity, buffer
• Digestive enzyme: aqueous solvent necessary for taste

Question 2

How does saliva maintain the pH?

Answer 2

Oral pH needs to be maintained at about 7.2 pH
- bicarbonate/ carbonate buffer system for rapid neutralisation of acids

Question 3

What is the flow rate and daily secretion of saliva?

Answer 3

• Flow rate: 0.3 to 7ml/minute
• Daily secretion of 800-1500ml in adults from major and minor glands

Question 4

What is the pH range for saliva?

Answer 4

6.2 to 7.4

Question 5

What are the two types of secretion for saliva?

Answer 5

• Serous secretion: alpha amylase, helps with starch digestion
• Mucus secretion: mucins for lubrication of mucosal surfaces

Question 6

Is the parotid gland serous or mucus?

Answer 6

Serous

Question 7

Is the submandibular and sublingual serous or mucus?

Answer 7

Both

Question 8

Is the minor glands serous or mucus?

Answer 8

Mainly mucous

Question 9

What are some factors that affect composition and the amount of saliva produced?

Answer 9

• Flow rate
• Circadian rhythm
• Type and size of gland
• Duration and type of stimulus
• Diet
• Drugs
• Age
• Gender

Question 10

What is inside saliva?

Answer 10

Secretion of proteins (help with defensive and digestive functions) and glycoproteins in a buffered electrolyte solution

Question 11

What ions help with the remineralisation of saliva?

Answer 11

Ca^2+, PO4^3-

Question 12

What are the three defence mechanisms?

Answer 12

• The oral mucosa (physical barrier)
• Palatine tonsils
• Salivary glands

Question 13

How does the palatine tonsils act as a defence mechanism?

Answer 13

• Lymphocyte subsets and dendritic cells
  Help with immune surveillance and resistance to infection

Question 14

How does the salivary glands act as a defence mechanism?

Answer 14

Saliva washes away food particles, bacteria or viruses
Used for metabolic support

Question 15

How does saliva help with immunity?

Answer 15

Salivary glands are surrounded by lymphatic system
– linked to thoracic duct and blood

Broad range of functional immune cells

Oral mucosa and glands have high blood flow rate

Question 16

What is the parotid gland?

Answer 16

When stimulated, this is where the main source of saliva comes from. Secretes serous saliva

Question 17

What is the difference between stimulated and unstimulated saliva?

Answer 17

Unstimulated saliva is dominated by SMG (submandibular) components

Stimulated has composition resembling parotid secretion

Question 18

What are the two epithelial tissue that compose the salivary glands?

Answer 18

• acinar cells
• ducts: collect to form large duct entering mouth

Question 19

How are the salivary glands equipped?

Answer 19

With channels and transporters in the apical and basolateral membranes enabling transport of fluid and electrolytes

Question 20

What are the two types of acini?

Answer 20

Acini - any of the smallest lobules of a compound gland
Serous acini and mucous acinus

Question 21

What are some features of serous acini?

Answer 21

• Dark staining
• Nucleus in basal third
• Small central duct
• Secrete water + α amylase

Question 22

What are some features of mucous acini?

Answer 22

• Pale staining : ‘foamy’
• Nucleus at base
• Large central duct
• Secrete mucous (water + glycoproteins)

Question 23

What is on the outside of acinus cells?

Answer 23

Myoepithelial cells which are squeezing the cell to get the saliva out

Question 24

What are the two types of cells that line the intralobular duct of the acini cells?

Answer 24

• Intercalated: short narrow duct segments with cuboidal cells that connect acini to larger striated ducts
• Striated ducts: striated like a thick lawn. major site for reabsorption of NaCl

Question 25

What are some features of striated ducts?

Answer 25

- appear striated at basal end - basal membrane highly folded into microvilli for active transport of HCO3 against concentration gradient - microvilli filled with mitochondria for energy to facilitate active transport

Question 26

How does the movement of substances change in the ducts?

Answer 26

No movement of water just isotonic plasma-like fluid secreted by acini (primary saliva)

Question 27

What do the ducts secrete and reabsorb?

Answer 27

Secrete: K+ and HCO3- Reabsorb: Na+ and Cl-

Question 28

What are the two routes of secretion?

Answer 28

- Regulated (leading to saliva across apical membrane) - Constitutive (leading towards interstitium and bloodstream

Question 29

What are the three pairs of major salivary glands?

Answer 29

- Parotid - Submandibular - Sublingual Contributes to 80% of salivary flow

Question 30

What are the glands responsible for 20% of salivary flow?

Answer 30

Minor salivary glands - submucosa of oral mucosa - lips, cheeks, hard and soft palate, tongue

Question 31

Where are the parotid glands and parotid duct located?

Answer 31

- Superficial triangular outline between: - Zygomatic arch (temple area) - Sternocleidomastoid (muscle behind ear to side of neck) - Ramus of mandible and masseter and med pterygoid (muscle on side of cheeck above jaw) (look at photo)

Question 32

What structures pass through the parotid gland?

Answer 32

- External carotid artery + terminal branches - Retromandibular vein - Facial nerve + branches to muscles of facial expression - Parotid capsule (very tough)

Question 33

What is the anatomical structure of the submandibular gland?

Answer 33

Two lobes separated by mylohyoid muscle: - larger superficial lobe - smaller deep lobe in flood of mouth

Question 34

Where is the submandibular duct?

Answer 34

- Also called Wharton's duct - Begins in superficial lobe - wraps round free posterior border of mylohyoid - runs alone floor of mouth - empties into oral cavity at sublingual papillae

Question 35

Where is the opening of the ducts at the sublingual papillae?

Answer 35

Lingual frenum (lift tongue up to roof of mouth and bit in the centre that attaches it to floor of mouth)

Question 36

Where are the sublingual glands?

Answer 36

between the mylohyoid muscle and oral mucosa of the floor of the mouth - This gland is variable in size with mixed acini (mainly mucous)

Question 37

Where are the minor salivary glands found in concentrated areas?

Answer 37

- Buccal labial - Palatal - Lingual regions - Superior pole of tonsils - tonsillar pillars - base of the tongue

Question 38

Are minor salivary glands mucous or serous

Answer 38

- all are mucous except serous glands of von Ebner - they lack a branching network of draining ducts: each salivary unit has its own simple duct

Question 39

What effect does sympathetic and parasympathetic stimulation have?

Answer 39

Stimulation of parasympathetic nerves causes the production of a copious flow of saliva while sympathetic stimulation selectively causes secretion of protein and glycoprotein

Question 40

What are the symptoms and causes of salivary gland disease and dysfunction?

Answer 40

- obstructive - inflammatory - degenerative - drug side effects - cancer

Question 41

What is Xerostomia?

Answer 41

Dry mouth - may be a consequence of cystic fibrosis or Sjogrens syndrome

Question 42

What are the causes of Xerostomia?

Answer 42

Medication and irradiation for head and neck cancers

Question 43

What are salivary calculi?

Answer 43

Saliva contains calcium and phosphate ions that can form these salivary calculi (Stones) - most often in the submandibular gland - they block the duct at the bend round the mylohyoid or at exit at sublingual papillae

Question 44

What can be some inflammatory effects?

Answer 44

- Infection secondary to blockage - Mumps (viral infection): fever, swelling of glands, pain over parotid

Question 45

Why can salivary glands become degenerative?

Answer 45

- complication of radiotherapy to head and neck for cancer treatment

Question 46

What are some drug side effects on salivary glands?

Answer 46

500 prescription drugs have sympatheticommetic effect: - act on NA (nicotinic acetylcholine) receptors or inhibit parasympathetic action at ACh receptors

Question 47

What are the effects of salivary gland dysfunction?

Answer 47

- If output falls to <50%, patient will have a dry mouth - Low lubrication, oral function difficult - Low oral hygiene (accumulation of plaque) - Infections (thrush)