SALIVA.
Dr. VISHNUDAS PRABHU
CONTENTS






INTRODUCTION
SALIVARY FLOW RATE
COMPOSITION
FUNCTIONS
CONTROL OF SECRETION
COMPOSITION OF ARTIFICIAL SALIVA
INTRODUCTION

Saliva is a complex fluid, produced by the salivary glands
whose important role is maintaining the well-being of the
mouth.

Saliva produced by major salivary gland differ from one
another in composition

Parotid gland secretes a watery saliva rich in enzymes like
amylase, proline rich proteins and glycoproteins.
Salivary glands
Major
Minor
• Parotid
- lingual mucous glands
• Sublingual
- labial glands
• Submandibular
-palatal glands
-buccal glands
-lingual serous glands

Submandibular gland contains high proportion of
glycosylated substances such as mucin.

Sublingual gland produces a viscous saliva rich in
mucin.

Secretion of all the major and minor salivary glands
contribute whole saliva.

It also contains desquamated oral epithelial cells,
microorganisms and their products, leukocytes, fluid
from gingival crevice, and food remanants.

Total volume of saliva secreted by humans is
approximately 750-1000ml/day.

Submandibular-60%,parotid-30%,sublingual-5% and
1%-minor salivary glands.

The pH of saliva ranges from 6.4-7.4 but for parotid
gland ranges from 6.0-7.8
•



Ducts of major salivary glandsparotid-stensen’s duct
submandibular-wharton’s duct
sublingual-bartholin’s duct
Structure of Salivary gland
THE SECRETORY UNIT
The basic building block of all salivary glands

ACINI - water and
ions derived from
plasma

Saliva formed in acini flows
down DUCTS to empty into
the oral cavity.
Salivary flow rate:
Exhibit diurnal and seasonal variations
 Peak : mid afternoon
spring
 Normal salivary flow rate:
O.1 to 0.4 ml/min(unstimulated)
1.5 -2 ml/min (stimulated)
During sleep flow is negligible.



Approximately 0.5litres of saliva is secreted
per day,of which 25%comes from
submandibular salivary glands and
66%from parotids.
During sleep flow rate is negligible.
Composition
saliva
Solids-0.5%
Water- 99.5%
Organic substances
Enzymes
Amylase(ptyalin)
Maltase
Lingual lipase
Lysozyme
Phosphatase
Carbonic anhydrase
kallikrein
Other organic substances
Inorganic substances
Albumin
Mucin
sodium
Proline rich proteins
Calcium
Lactoferrin
potassium
IgA
Bicarbonates
Blood group antigens
Bromide
Free amino acids
Chloride
Nonprotein nitrogenous
Fluoride
substancesPhosphate
Urea,uric acid
creatinine,xanthine
gases
Oxygen
Carbon dioxide
nitrogen
FUNCTIONS
Important function of the salivary gland is production
and secretion of saliva.
PROTECTION:
 Constant secretion of saliva prevents desication of
oral tissues.
 Absence of which leads to degeneration and atrophy.


Fluid like nature provides a washing action to flush
away debris and the non adherent bacteria.





Saliva protects the mucosa from chemical and
thermal insults.
LUBRICATION:
Saliva has high molecular weight glycoproteins
responsible for oral, oropharengeal and oesophageal
mucosal lubrication.
BUFFRERING:
Buffering system of saliva is mainly from
bicarbonate and to some extent phosphate ion.


Metabolism of salivary proteins and peptides provide urea
and ammonia to increase the pH.
This high pH is nonconductive for cariogenic
bacteria to survive, ferment carbohydrate and
produce acid to cause tooth decay.
FORMATION OF ENAMEL
PELLICLE



Salivary protein called proline rich protein and
statherin, a small tyrosine rich protein inhibit
precipitation of calcium phosphate.
Along with salivary glycoprotein, statherin and
certain of the proline rich protein bind to tooth
surface forming acquired enamel pellicle.
Resulting super saturation of calcium and phosphate
reduces dissolution and promotes remineralization.



On the surface of the tooth a high concentration of
calcium and phosphate cause posteuruptive
maturation of the enamel.
Increases surface hardness and resistant to
demineralization.
Remineralization is enhanced by flouride ions in
saliva.




ANTIBACTERIAL :
The acinar cells secrete peroxidase and ductal cells
secretes thiocyanate which establishes bactericidal
system of saliva.
Peroxidase in presence of hydrogenperoxidase and
thiocyanate catalyses the formation of
hypothiocyanate which is inhibitory to bacteria.
Lysozyme hydrolyzes the bacterial cellwall resulting
in cell lysis.




ANTIOXIDANT :
Antioxidant defense mechanism is exerted by uric
acid and ascorbic acid .
Profound amount is secreted by the parotid during
meal times.
This helps in reducing oxidant stress and maintain
oral integrity.




Another antibacterial substance present in saliva is
lactoferrin an iron binding protein.
In the presence of specific antibody, lactoferrin
which is not saturated with iron enhances the
inhibitary effect of the antibody on microorganisms.
DIGESTION:
Digestive function is mainly due to presence of
salivary amylase, lingual lipase enzymes.





Salivary amylase acts on ingested carbohydrate to
produce glucose and maltose.
Lingual lipase produced by the lingual serous glands
initiates the digestion of dietary lipids hydrolyzing
triglycerides to monoglycerides and diglycerides.
MASTICATION AND DEGLUTITION:
Saliva moistens the food and helps its breakdown
into smaller particles to initiate digestion.
Helps in the formation of bolus and facilitate
deglutition.






TASTE SENSATION:
Saliva will emulsify the food taken which is a
prerequisite for the sense or percepion of taste.
SPEECH:
Saliva keeps the oral tissue moist and well lubricated
facilitating speech.
EXCRETION:
Many substances from blood reach the saliva, thus
can be considered as a route of excretion.
Multifunctionality
Amylases, Cystatins,
Carbonic anhydrases,
Histatins, Mucins,
Histatins
AntiPeroxidases
Buffering
Bacterial
Amylases,
Cystatins,
Mucins, Lipase
AntiMucins
Digestion
Viral
Salivary
Families
MineralAntiization
Fungal
Cystatins,
Histatins
Histatins, ProlineLubricatrich proteins,
Tissue ion &ViscoStatherins
Coating elasticity
Amylases,
Cystatins, Mucins,
Mucins, Statherins
Proline-rich proteins, Statherins
adapted from M.J. Levine, 1993
FORMATION AND SECRETION

It has two stages of formation.

First stage - cells of secretory end piece &
intercalated duct produce primary saliva. It is
isotonic fluid, containing most of the organic
components & H2O secreted by gland.

Second stage - primary saliva modified as it passes
through the striated & excretory ducts by
reabsorption & secretion of electrolyte. Final saliva
is hypotonic.

Protein secretion occur by exocytosis , ie fusion of
secretory granules with the luminal membrane to
release their content into lumen.
TWO STAGE HYPOTHESIS
OF SALIVA FORMATION
Most proteins
Water &
electrolytes
Na+ Cl- resorbed
Some proteins
Isotonic
primary saliva
electrolytes
K+ secreted
Hypotonic
final saliva
into mouth

REGULATION OF SALIVARY SECRETION

It is regulated only by nervous mechanism.
Autonomic nervous system is involved in the
regulatory function.
Nerve supply to salivary glands

Parasympathetic fibers to submandibular and sublingual glands
superior salivatory nucleus situated in pons
Submaxillary ganglion
submandibular and sub lingual glands
•
Parasympathetic fibers to parotid gland
inferior salivatory nucleus
End in the otic ganglion
Parotid gland

FUNCTION-

On stimulation of parasympathetic fibers, profuse and watery
saliva is secreted. These fibers activate the acinar cells and
dilate the blood vessels of salivary glands through
neurotransmitter acetylcholine.

•
SYMPATHETIC FIBERS
Lateral horns of first and second thoracic segments of spinal
cord.
Superior cervical ganglion
Salivary glands

FUNCTION-
•
The stimulation of sympathetic fibers causes less
secretion of saliva,which is thick and rich in mucus.it
is because these fibers activate acinar cells and cause
vasoconstriction by secreting nor adrenaline.

Conditions that affect salivation
Physiologic

Taste

Surface texture

Dehydration

Age

Mastication

Emotion
Pathologic conditions that increase salivation

Digestive tract irritants

Ill fitting dentures/inadequate interocclusal distance

Vitamin deficiency

Trauma from surgery

Pathologic conditions that decrease
salivation
Senile atrophy of the salivary glands
Irradiation therapy
Dieseases of the brain stem
Diabetes mellitus/ insipidus
Diarrhoea
Acute infectious diseases

Drugs that increase salivation
Cholinesterase inhibitors. Ex.prostigmine
Adrenergic stimulating drugs. Ex.epinephrine
Sialogogues. Ex.pilocarpine.

Drugs that decrease salivation
•
Antihistamines
Antianxiety agents
•
Antidepressant
Anti arrhythmic agents
•
Drugs for peptic ulcer
•
Antiparkinsonian drugs
•
Antisialogogues
•
Diuretics
•
Decongestants
Antipsychotics
Xerostomia
Dry mouth
•
Due to hyposalivation or aptyalism
•
Causes of this disease are:

-dehydration or renal failure

-sjogren’s syndrome

-radiotherapy

-trauma to salivary gland

-side effect of drugs like antihistamines, antidepressants and
antiparkinsonian drugs

-shock
•

Drooling

-It occurs in following conditions:
• Uncontrolled flow of saliva (ptyalism)
• Teeth eruption
• Upper respiratory tract infection
• Tonsillitis
• Peritonsillar abscess

Chorda tympani syndrome
•
•
Condition characterised by sweating while eating
Some paraympathetic fibers get severed during
surgical procedure and during regeneration some
nerve fibers that run along with chorda tympani
branch of facial nerve may deviate and join fibers
supplying sweat glands.
Sjogren’s syndrome
•
•
Autoimmune disorder in which the
immune cells destroy exocrine glands such
as lacrimal and salivary glands
Common symptoms are -dryness of
mouth
-persistent cough
-dryness of eyes
REFERENCES
1)
2)
3)
4)
Orban’s Oral Histology & Embryology-12th
Edi
Tencate’s Oral Histology-7th Edi
Salivary Diagnostics- David T Wong
Histology For Pathologist- S S Sternberg2nd Edi