SALIVA

Dr. Nitika Jain

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contents

• Introduction• Salivary gland anatomy• Secretion of saliva• Composition of saliva

– Organic components– Inorganic components

• Functions of saliva

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What is saliva

• Saliva serves multiple and important functions. Three major, paired salivary glands produce the majority of saliva: the parotid, the submandibular, and the sublingual glands. In addition, 600-1,000 minor salivary glands line the oral cavity and oropharynx, contributing a small portion of total salivary production.

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Major salivary glands

• Parotid• Sub – mandibular• Sub - lingual

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Salivary gland - secretion

• Serous: very thin and wateryo parotid glando lingual glands of von Ebner

(serous glands of von Ebner)

Serous acini

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• Mucous: very thick and viscouso palatine glandso posterior lingual glandso labial buccal glands

Mucous acini

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• Mixed secretions: mix of the twoo Sublingual glands

– Mostly mucous with some serouso Submandibular glands

– Mostly serous with some mucouso Anterior lingual glands

– Mixed secretion

Mixed: mostly serous acini (dark), partially mucous acini (light

cells)

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Parotid gland

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Parotid gland

• Largest of all the salivary glands• Purely serous gland which

produces thin, watery, amylase rich saliva

• Superficial portion lies in front of the external ear and deeper portion lies behind the ramus of the mandible

• Stensons duct– Open out adjacent to maxillary

second molar

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• It is 5.8 cm in the craniocaudal dimension, and 3.4 cm in the ventral-dorsal dimension.

• Weight is 14.28 g. It is irregular, wedge shaped, and unilobular.

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• Superior border – Zygoma • Posterior border – External

Auditory Canal • Inferior border – Styloid Process,

Styloid Process musculature, Internal Carotid Artery, Jugular Veins

• Anterior border – a diagonal line drawn from the Zygomatic to external auditory canal.

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• Stensen’s duct arises from the anterior border of the Parotid and parallels the Zygomatic arch, 1.5 cm inferior to the inferior margin of the arch. Stensen’s duct runs superficial to the masseter muscle, then turns medially 90 degrees to pierce the Buccinator muscle at the level of the second maxillary molar where it opens onto the oral cavity.

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Sub – mandibular gland

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Sub – mandibular gland

• Second largest salivary gland• Produces 65-70% of total saliva

output• The duct is called Wharton’s duct• Wharton’s duct exits on the floor of

the mouth opposing the lingual surface of the tongue

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• Located in a depression on the lingual side of the mandibular body

• Innervated by parasympathetic nerve endings and possesses NO sympathetic receptors

• The parasympathetic fibers arrive through the facial and glossopharyngeal nerves

• Mixed secretion – mostly serous

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Sub – lingual gland

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Sub – lingual gland

– Smallest of the major glands– Produce less than 5% of total saliva

output• Saliva delivered via the ducts of Bartholin • The Bartholin ducts exit on the base of

the lingual surface of the tongue– Innervated by parasympathetic fibers – Little or no sympathetic influence – Mixed secretion – mostly mucous

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Minor salivary glands

• Minor salivary glands are found throughout the mouth: – Lips– Buccal mucosa (cheeks)– Alveolar mucosa (palate)– Tongue dorsum and ventrum – Floor of the mouth

• Together, they play a large role in salivary production.

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Histology of salivary gland

• The acini are the primary secretory organs but the saliva is modified as it passes through the intercalated, striated, and excretory ducts before being discharged into the mouth and oropharynx.

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• The serous cells contain numerous proteinaceous secretory (zymogen) granules. These granules contain high levels of amylase. In addition, the secretory cells produce kallikrein,lactoferrin, and lysozyme.

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Saliva

• General characterstics:Consistency - slightly cloudy due to

presence of mucins and cells Reaction - usually slightly acidic

(pH 6.02-7.05).On standing or boiling, it loses Co2 and becomes alkaline.

Specific gravity - 1.002-1.012 Freezing point - 0.07-0.34° Celsius

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• Percentage contribution of different salivary glands during unstimulated saliva:

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Unstimulated flow

• resting salivary flow―no external stimuluso Typically 0.2 mL – 0.3 mL per minuteo Less than 0.1 mL per minute means

the person has hyposalivation

Hyposalivation – not producing enough saliva

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Stimulated Flow

• response to a stimulus, usually taste, chewing, or medication eg, at mealtimeo Typically 1.5 mL – 2 mL per minuteo Less than 0.7 mL per minute is

considered hyposalivation

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The average person produces approximately 0.5 L – 1.5 L per day

• Salivary flow peaks in the afternoon

• Salivary flow decreases at night.• There is a difference in the quality

between stimulated and unstimulated saliva

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Ions and salivary flow

As saliva passes through the salivary ducts, cations (sodium and chloride)are reabsorbed into the adjacentblood vessels.

As saliva passes through the salivary ducts, cations (sodium and chloride) are reabsorbed into the adjacent blood vessels. In exchange, bicarbonates and potassium are transferred from the blood

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Stimulated Salivary Flow• Saliva passes through the salivary duct very rapidly o It impedes the exchange of sodium and chloride for

potassium and bicarbonate

Unstimulated Salivary Flow• Has a high content of potassium and bicarbonate oThe quality of unstimulated saliva will change when

flow increases because of a stimulus (chewing gum, thinking about lemons, looking at a food you crave)

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composition

• Water content - 99.5%• Solids - 0.5%

Inorganic content - 0.2% Organic content - 0.3% Gases - 1ml

oxygen/100ml - 2.5ml

nitrogen/100ml - 50ml

carbondioxide/100ml Cellular elements

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Organic Components of Saliva

Enzymes:• Amylase – converting starch into

glucose and fructose • Lysozymes – prevents bacterial

infections in the mouth • Histatins – prevents fungal

infections • Secretory IgA – immunity mediator

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• Lactoperoxidases – stimulation of minor salivary glands

• RNase and Dnase – cellular maintenance

• Lipase – initiates digestion of fat • Kallikrein – vasoreactive

substances

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Cellular Composition

• The cellular composition consists of:

• Epithelial cells • Neutrophils • Lymphocytes • Bacterial flora

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-Amylase

• Present in parotid saliva at conc. of 60-120 mg/ 100ml in submandibular

saliva at approx. 25 mg/100 ml.

• Very little amylase activity in the sublingual and minor glandular secretions.

• 6 isoenzyme forms exist; alpha-amylase (ptyalin) is Ca++ dependent and

readily inactivated by a pH of 4 or less.

• The enzyme hydrolyses the alpha 1:4 glycosidic bond between glucose units

in the polysaccharide chain of starch.

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Lysozyme

• An antibacterial enzyme.

• The mean concentration in whole saliva

– resting: 22 mg/100ml.

– Stimulated: 11 mg/100 ml.

• Lysozyme acts on the B (1-4) bond between N-acetyl-muramic acid and N-

acetyl glucosamine in the Gram positive bacterial cell wall component.

• Lysozyme may also be bactericidal,

• Inhibits mucosal colonization by microbial aggregation.

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 Kallikrein

•Splits serum beta-globulin into bradykinin

•Functional vasodilatation to supply an actively secreting gland.

Dextranases

Increased whole saliva dextranase levels may be associated with

impaired oral hygiene and over consumption of sucrose and

related fermentable carbohydrates which support the growth of

organisms producing dextranases.

Invertases

•High invertase activity is based on the involvement of several

enzymes chiefly derived from dental plaque S.Mitis and

S.Salivarius.

• High invertase activity ---- consume high sucrose and it usually

parallels with high lactobacillus and streptococcus counts of

plaque. 

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Glycoprotein (Mucins)

• Lubricant

• Types—MG1 & MG2

• Polypeptide chain that stick together

• Low solubility, High viscosity, Strong

adhesiveness

• Aids in mastication, speech, swallowing by

lubrication

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Glycoprotein (Mucins)

• Preserve mucosal integrity

• Protective barrier against excessive wear

• Antibacterial action by selective adhesion of microbes to oral tissue surface

• Barrier against acid penetration

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MG1

• High molecular-wt

• Adsorbs tightly to tooth surface--

enamel pellicle formation--Protection

from acid challenges

• High in caries susceptible patients

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MG2

• Low molecular wt

• Binds to enamel but get displaces

easily

• Promotes the aggregation and

clearance of oral bacteria (S.mutans)

• High in caries resistant cases

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Secretory leucocyte proteinase inhibitor (SLPI)

Proteinase inhibitory property

Antimicrobial and antiviral

Imp. Role in wound healing

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Tissue inhibitors of metalloproteinase

Remodeling of extracellular matrix in

inflammation

Growth promoting activity

Stimulation of osteoclastic bone resorption

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Immunoglobulins

• Secretory IgA is the predominant immunoglobulin - 20mg/100ml

• 90% of the total parotid lgA

• 85% of whole saliva lgA

• 30-35% of which is derived from minor glands, IgG (1.5 mg/100ml) & IgM (0.2 mg/100ml)

• Secretory IgA is synthesized by plasma cells within the glands in addition to the mucosal

epithelial cells.

• Secretory IgA --- non-lymphoid-derived glycoprotein designated as the secretory

component.

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Immunoglobulins

• This IgA exhibits 3 possible functions:

-Inhibition of bacterial colonization, probably by

agglutination.

- Binding to specific bacterial antigens involved with

adherence.

-Affecting specific enzymes essential for bacterial

metabolism.

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Structural features of salivary proteins

• Proline – rich proteins

• Statherins

• Cystatins

• Histatins

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Proline-rich protein (Glycoprotein)

70% of total secretory proteins

Acidic (Large), Basic (Small)

Present in enamel pellicle

Larger PRP promote bacterial attachment

Smaller reduces the initial bacterial attachment

A.Viscosus, S.mutans, S.Gordoni

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Statherin (Phosphoprotein)

• Is a small phosphoprotien (12000 daltons) relatively

rich in tyrosine and proline which has the property of

inhibiting Hydroxyapatite crystal growth.

• Potential precursor of enamel pellicle

• Inhibit spontaneous precipitation of cal.

phosphate in saturated solution

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Cystatins

• Several cystatins are

phosphorylated and bind to HA

• Inhibit crystal growth of Cal.

Phosphate salts

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Histatin

• Parotid and Submandibular saliva

• Bind to HA, precursor of acquired pellicle

• kills C.Albican in yeast form and mycelia form

• Bacteriostatic

• Inhibit hem agglutination and thereby

colonization

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Other organic compounds

Free Amino acids- (Below 0.1 mg/100 ml)o Too low to provide nutrient source

for bacterial growth Urea (12-20 mg /100 ml)

o Hydrolyzed by bacteria with the release of Ammonia---Rise in pH

Glucose (0.5- 1 mg/ 100ml)o Too low for bacterial growtho Increase in DM

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Lipids

Cholesterol, fatty acid

glycerides,

phospholipids

Corticosteroids

Cortisol and cortisine

1-2 mg/100ml

Vitamins

Water soluble vitamins5304/08/2023 SALIVA

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Function of saliva

Protective properties:– Lubrication – Maintenance of mucous membrane

integrity– Soft tissue repair– Dilution and clearance– Aggregation– Action of lactoferrin– Salivary peroxidase system– Antifungal activity

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Function of saliva

– Antiviral activity

– Buffering capacity of saliva

– Maintenance of tooth integrity

• Digestion

• Taste

• Saturation

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Lubrication

• Coat the food, the oral soft and hard tissues.

• Allows food to travel through the digestive system surfaces with

minimal friction.

• Without appropriate lubrication, food is retained and impacted

around the teeth,

• Both mg1 and mg2 can provide fluid layers with high-film strength

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Maintenance of mucous membrane integrity

Salivary mucins possess rheological properties that include

low solubility, high viscosity, elasticity, and adhesiveness.

Provide an effective barrier against desiccation and

environmental factors

Protect the underlying cells from sudden changes in osmotic

pressure.

Second line of defense against protease activity-cysteine

containing phosphoprotien

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Soft tissue repair

• EGF involved in oral wound healing

• Hormone like properties in stimulating

epithelial cells

• Parotid gland is the major source

• VEGF also known as vasculotropin---- an

angiogenic cytokine

• PAF ---- a potent phospholipid mediator

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Dilution and clearance

 Saliva dilutes and eliminates dietary sugars

and acids

This process is dependent on flow rate and

swallowing frequency

Oral sugar clearance extensively prolonged

when unstimulated whole saliva flow rate is

below .2ml/min

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Aggregation Inhibit bacterial attachment

Inhibits the adherence of these cariogenic organisms to teeth

and protection against caries.

Clumping of bacteria

Hinder effective adherence

Expectorated or swallowed

Histidine-rich peptide has growth-

inhibitory and bactericidal effects on oral

bacteria.

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Action of lactoferrin

• Lactoferrin, the exocrine gland secretion

• The bacteriostatic properties are attributed to the ability of the

unsaturated protein to bind two iron atoms per molecule

• Lactoferrin is capable of both a bacteriostatic and a bactericidal

effect on S mutans that is distinct from simple iron deprivation.

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Action of salivary peroxidase

• The antimicrobial effect of salivary peroxidase against S mutans is

significantly enhanced by interaction with secretory lgA.

• Interaction with each other and with high molecular weight mucin.

This mucin serve to concentrate a defense force on the mucosa

against the external environment, entrapping and incapacitating

microorganisms.

 

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Antifungal activity

• Parotid fluid has an antifungal capacity, reflecting properties

of both the neutral and the basic histidine rich peptides.

• Pollock and others showed that the basic peptides could

cause 99% loss of viability of Candida albicans at levels of

25 mg/ml,

• Oppenheim and others found that the neutral histidine rich

peptide was a potent inhibitor of C. albicans germination at

levels as low as 2 mg/ml.

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Antiviral activity

• Antibodies (secretory lgA) can directly neutralize viruses.

• Mucins are also effective antiviral molecules.

• A major function of saliva is to prevent the establishment of

unwanted species in the first place

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Buffering capacity Resistance to pH changes at an arbitrary point.

3 buffer systems :

o Carbonic acid / bicarbonate

o Phosphate

o Protein

o CO2 + H2O H2CO3 H+ + HCO3-

o Concentration of bicarbonates is highest in parotid saliva

CA CA

pH

Secretion rate

Buffer capaci

ty

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Maintenance of tooth integrity

• Physical flow of saliva (the hydrokinetic property) coupled

with muscular activity,

• Small decrease in the resting salivary flow rate can greatly

prolong sugar clearance time.

• Interaction with saliva provides a post eruptive maturation

through the diffusion of ions

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• This enrichment of the crystal structure increases hardness,

decreases permeability, increases resistance to caries.

• The original pellicle is replaced by a constantly replenished

salivary film selectively absorbed proteins with a

high affinity for hydroxyapatite provides a protective

barrier

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Digestion

SALIVARY AMYLASE

STARCH DIGESTION

STARCH CLEARANCE

LIBERATING MALTOSE

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Saliva is formed in 2 stages :

 • A primary secretion

occurs in the acini

• Then modified as it passes through the ducts

Mechanism of saliva formation

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METHOD OF COLLECTING SALIVA

Passive drool

Oral swab

Infant swab

Spitting method

Suction method

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• • Avoid alcohol for 12 hours before sample collection.

• • Avoid eating major meal within 60 minutes of sample collection.

• • Avoid dairy products for 20 minutes before sample collection.

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• Avoid foods with high sugar or acidity, or high caffeine content, immediately before sample collection, since they may compromise the assay by lowering saliva pH and increasing bacterial growth.

• • Rinse mouth with water to remove food residue before sample collection. Wait at least 10 minutes after rinsing before collecting saliva to avoid sample dilution.

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Prior to saliva collection

• Participants should rinse with water 10 minutes prior to collection.

• Cut plastic drinking straws into 2-inch (5 cm) pieces.

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PASSIVE DROOL

• Passive drool is highly recommended because it is cost effective and approved for use with almost all analytes. To avoid problems with analyte retention or the introduction of contaminants, use only high quality polypropylene vials for collection, such as our 2 ml cryovials. The vials used must seal tightly and be able to withstand temperatures as low as -80ºC.

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Instructions to the patient

• Allow saliva to pool in the mouth.• With head tilted forward,

participants should drool down the straw and collect saliva in the cryovial. (It is normal for saliva to foam, advise using a vial with twice the capacity of the desired sample volume.)

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• Repeat as often as necessary until sufficient sample is collected. One mL (excluding foam) is adequate for most tests. Collection of samples to be analyzed for multiple analytes may require larger vials.

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Salimetrics Oral Swab (SOS)

• Participants who are not willing or able to drool saliva into a vial.

If the saliva samples are to be analyzed for cortisol, testosterone, α-amylase, chromogranin A, cotinine, C-reactive protein, or SIgA, the Oral Swab is an excellent alternative to passive drool because of its ease of use. The SOS also helps filter mucus from the sample, help improve immunoassay results.

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Children and infant swab

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To be continued…

• Saliva as a diagnostic marker• Diseases• Xerostomia• Conclusion