Constituents of Saliva

Question 1

What type of saliva is produced from:

• parotid:
• submandibular:
• sublingual:

In terms of volume, how much saliva is produced over the course of the day?

• unstimulated flow rate?
• stimulated?

Answer 1

• parotid: 99% serous - watery saliva
• submandibular: mixed serous and mucous
• sublingual: largely mucous secretions - viscous saliva with more mucoproteins

500-700ml/day: 90% from major glands

~0.3ml/min at rest - unstimulated rate

~1.75ml/min when stimulated

Question 2

Where does saliva come from at rest?

When stimulated?

What is whole saliva?

Answer 2

At rest:

• 70% from submandibular

When stimulated:

• 60% from parotid
• 30% from submandibular

Whole saliva: mixture of everything, will include gingival crevicular fluid, bacteria and food debris

Question 3

List some factors influencing stimulated flow rate:

Answer 3

• gland size
• age
• food intake
• vomiting
• visual stimulus
• increased presence of food in mouth: chemical (taste/smell), mechanical (chewing)
• increased in thought/smell of food
• time of day: afternoon increased, night decreased
• season: winter>spring>autumn>summer
• drugs: acting on glands or nerves

Question 4

What is the impact of lack of saliva?

Answer 4

• increased caries
• mucosal infections especially fungal
• pain from oral mucosa
• difficulty chewing, swallowing, speaking
• impaired taste

Question 5

What is the composition of saliva?

What are the main electrolytes in saliva?

Answer 5

• water >99%, important in most functions
• electrolytes/inorganic constituents
• formed elements/organic comstituents
• hypotonic in relation to plasma

Cations: Na and K, Ca, Mg

Anions: Cl, HCO3, phosphates, thiocyanate, SO4, F, I, OH

Question 6

What is the buffering action of saliva?

Answer 6

HCO3 - bicarbonate:

• at rest, salivary pH is around neutral
• concentration increases with flow rate (as does salivary pH)
• minimises drop in pH around teeth after consumption of sugar/acids –> minimising demineralisation of teeth
• phosphate and protein buffers

Question 7

How does saliva assist in mineralisation of teeth?

Answer 7

• saliva is supersaturated with Ca and PO4
• high flow rates associated with increase in Ca, PO4, OH and pH
• prevents demineralisation of teeth
• encourages remineralisation of teeth
• increases calculus formation as a biproduct
• assisted by presence of fluoride in saliva

Question 8

What is the role of salivary amylase?

What is the role of salivary lipase?

Answer 8

1st stage of carbohydrate digestion - breaks down polysaccharides (starch) to disaccharides (maltose)

• inactivated by stomach acid
• may be important in breaking down polysaccharides, starch in plaque/around teeth

Salivary lipase - from lingual minor glands

• 1st stage of fat digestion - keeps taste buds clear, digestion of milk in infants
• remains active at gastric pH

Question 9

What is the role of mucous glycoproteins (mucins)?

What is statherins function?

Answer 9

• lubricate, coat all oral soft tissues: prevent drying, providing a barrier
• important part of pellicle
• aggregate bacteria
• nourish some bacteria

Statherin: prevents precipitation of Ca and PO4 from saliva

• good for mineralisation of teeth
• can prevent some calculus formation

Question 10

List some antimicrobial actions of saliva:

Answer 10

• water: cleansing
• mucins: aggregation of bacteria
• amylase: interferes with bacterial adherence
• lysozyme: hydrolyses some bacterial cell walls
• peroxidase/thiocyanate: poisons bacteria
• lactoferrin: deprives bacteria of iron
• histatins: antifungal and antibacterial
• cystatins: inhibit tissue damaging bacterial enzymes