Saliva Flashcards
Salivary glands
3 main pairs. Produce saliva which is colourless, slightly sticky solution.
Parotid glands - largest and situated either side of face. Duct opens by upper second molar. Produce mainly serous saliva. 25% saliva produced here.
Submandibular glands - second largest and lie in submandibular fossa on inner aspect of mandible. Ducts open on floor of mouth. Produce mixture of serous and mucous saliva. 70% saliva produced here.
Sublingual glands - smallest and lie in sublingual fossa on inner aspect of mandible. Ducts open in floor of mouth . Produce mainly mucous saliva. 5% saliva produced here.
Very small amounts produced by excessory glands.
Saliva
Secreted from specialised secretory cells of the glands and either serous or mucous.
Approx 0.5-1L produced daily by average adult. Secreted into oral cavity by ducts which open onto the surface of oral mucosa. Produced my 3 main pairs of salivary glands but also minor accessory glands scattered throughout oral cavity producing very small amounts. Saliva is constantly flowing under normal conditions. It reduces significantly during sleep but doesn’t stop.
Composition of saliva
Water = 99.42% Inorganic = 0.22% Organic = 0.22% Enzymes = 0.14%
Inorganic and organic content
- Inorganic content - principal ions(salts) are calcium and phosphates. Calcium associated with formation of calculus and remineralisation. Other small quantities of other salts ie mg, Zn, Na.
Gases - when saliva is first formed it contains 02, N2 and CO2 in glands under pressure and CO2 levels are high. Once saliva reaches oral cavity the gases are released. CO2 released linked with calculus formation. - Organic content - several types of proteins in saliva.
a. Mucoids( glycoproteins). This gives saliva mucous properties and viscosity. This is important for formation of bolus, provides protective barrier for soft tissue. If too much not enough washing away.
b. Serum proteins: serum albumin and serum globulin. These indirectly have an antibacterial effect.
c. Waste products- urea and uric acid which are waste products of protein metabolism.
Enzymes
Saliva contains many enzymes , some produced in glands and some a by product found in oral cavity.
1. Amylase - breaks down carbohydrates. Produced in salivary glands.
2. Lactoparoxidase - found in whole saliva. Produced in oral cavity and has an antibacterial function.
3. Lysozyme - produced in glands and so found in pure saliva. Has an antibacterial function. Effect is diminished when mixed with mucoids.
Additives within mouth - food, bacteria and microorganisms, cellular debris , Leukocytes originated from gingival crevice.
Flow of saliva
Saliva flow varies from one individual to another in both quality and quantity. Also rate of secretion varies depending on time of day eg sleep.
Stimulants that may increase flow:
- eating, smelling, sight of food, strongly flavoured foods, chewing gum , any irritant in the mouth ie fractured sharp tooth.
Some things decrease flow:
- medication, antidepressants, strong painkillers, diabetic medication, blood pressure medications, age, alcohol , blocked salivary glands, smoking, when frightened.
Xerostomia
Severe, inhibited flow of saliva that results in a very dry mouth. Usually a chronic condition needing careful management.
People with Sjögren’s syndrome , patients who have received radiotherapy to head and neck, patients who have had surgery on salivary glands, in elderly due to atrophy of glands.
Oral consequences:
- higher caries risk and caries in unusual areas, sore red mouth, brushing and eating difficulties, inflamed gingival tissues, halitosis due to washing away lost.
Management :
- good oral hygiene, high fluoride toothpaste, sprays and other saliva replacements, fluoride mouthwash that’s alcohol free, see patient regularly( supportive care).
Ph of saliva
Usually has a Ph of 6.7 approx but may vary. Fresh whole saliva is usually slightly acidic. Ph is affected by food, drinks, toothbrushing etc.
A low Ph associated with higher caries rate.
A high Ph is often seen in individuals who form a lot of calculus.
Saliva and dental caries
Viscosity - if saliva is too thick you increase chance of debris adhering to your teeth. When added to other factors ie poor oral hygiene this can cause problems.
Quantity - adequate flow is important for natural cleansing. If you have a dry mouth this increases your susceptibility to caries.
Ph - buffering power will be poor if there’s no adequate flow or wrong Ph.
Saliva and lip apart posture
Some individuals keep mouth slightly open when relaxed. People with lip apart posture are usually mouth breathers meaning too much evaporation of saliva. This causes problems including :
- staining, plaque build up, gingival inflammation( usually confined to exposed area of mouth)
How can we help?
- Vaseline over teeth and gums at night , good oral hygiene, corsodyl gel on inflamed tissues.
Functions
DIGESTIVE - amylase begins process of carbohydrate digestion by converting starch into maltose.
LUBRICATING - glycoproteins provide viscosity to enable clear speech, mastication and deglutition.
WATER BALANCE - dry mouth reflex is excessive evaporation of saliva which acts as stimulus to salivary flow. If body tissues are in need of water ie dehydrated reflex does not occur and thirst follows.
ANTIBACTERIAL - mechanical action ie removing bacteria conveying to stomach and destroyed by gastric juices. Antibacterial enzymes lysozyme , lactoperoxidase , serum globulin eg immunoglobulin IgA other antibodies and Leukocytes from gingival crevice.
EXCRETORY - minor function involving swallowing of bacteria and conveyed to stomach where destroyed.
* TASTE - sensation of taste produced only by substances in solution .
NATURAL CLEANSING - helping to wash away debris. Rapid multiplication of bacteria and debris would readily accumulate on teeth and mouth is saliva was not present.
* BUFFERING - power to resist changes of Ph when acid or alkali added. Salivary buffers consist of bicarbonates, phosphates and proteins. Bicarbonates most powerful against acids , important in increasing Ph levels after eating.
