The document discusses the three pairs of major salivary glands, their cell types, secretions, and role in digestion. It describes how saliva is modified as it passes through the ducts via ion transport processes. Finally, it outlines the functions of saliva including lubrication, protection of teeth, and initial digestion of starches through the enzyme ptyalin.

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Dr. Anju Jha
Assistant Professor
 There are three pairs of major salivary glands:
Parotid glands
Submandibular glands.
Sublingual glands.
 Several minor glands are there, which are scattered
throughout the mouth and pharynx.

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 Salivary glands contain mainly two types of cells:-
mucus cells
 serous cells
 These cells are arranged in the form of acini.
 Parotid glands: Purely serous. watery secretion—
contain ptyalin.
 Submandibular glands: Contain both type of cells
but predominantly serous.
 Sublingual glands: Also mixed but predominantly
mucous (viscous secretion - contain mucin).

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 The acini and the ducts are surrounded by
myoepithelial cells.
 Myoepithelial cells help in squeezing the secretions
into the mouth.
Nerve Supply of Salivary Glands
 All glands receive both sympathetic and
parasympathetic nerve supply

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Composition of Saliva
 Mixed saliva is
 Colorless,
 Viscous,
 Opalescent
 Quantity — 1-1.5 L/day
 pH— slightly less than 7.0 therefore acidic
 Normal contribution
 Submandibular glands — 70% (of resting volume of saliva),
 Parotid glands — 25%,
 Sublingual gland — 5%

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saliva
Solids
0.5%
Organic
solids
2/3
Inorganic
solids
1/3
Water
99.5%
Organic solutes
Mucin (glycoprotein)
Enzyme ptyalin
(salivary amylase).
Maltase, Lysozyme,
Kallikrein, Lipase
Antibodies IgA
Blood group substances
Urea, uric acid, creatinine,
free amino acids
Inorganic solutes
Na+ ,K+, Cl-, HCO3-
PO4- and Br- in
traces
A rise of pH produced by loss of CO2 or by bacterial action causes
precipitation of salivary constituents and their deposition on the teeth as
tartar.

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 Salivary secretion is a two-stage operation:
1st stage involves the acini, and
2nd stage involves the salivary ducts.
First stage –
 The acini secrete a primary secretion.
 Primary secretion contains ptyalin and/or mucin in a
solution of ions.
 Concentrations of primary secretion not much
different from those of typical extracellular fluid.
 Second stage –(Primary secretion flows through the
ducts)
 Modification of the ionic composition of the fluid in
the saliva.
 Two major active transport processes take place.
1st Na+ ions are actively reabsorbed from all the
salivary ducts and K+ Ions are actively secreted in
exchange for the sodium.
2nd HCO3- ions are secreted by the ductal epithelium
into the lumen of the duct.

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 There is excess Na+ reabsorption compared with K+
secretion.
 It creates electrical negativity of about −70 millivolts
in the salivary ducts.
 This negativity in turn causes Cl- to be reabsorbed
passively.
 Therefore, the Cl- concentration in the salivary fluid
falls to a very low level.
 There is passive exchange of bicarbonate for chloride
ions, and partly from an active secretory process.

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Ions Concentration
in Saliva
Comparison to
plasma
Na+ ion 15 mEq/L 1/7th to 1/10th
Cl – ion 15 mEq/L 1/7th to 1/10th
K+ ion 30 mEq/L 7 times
HCO3- ion 50 to 70 mEq/L 2-3 times
Salivary secretion in resting stage
During maximal salivation
 The rate of formation of primary secretion by the acini
can increase as much as 20-fold.
 Rapid flow through ducts.
 Ductal reconditioning of the secretion is reduced.
 Copious quantities of saliva are being secreted.
 Na+ & Cl- ions concentration is about 1/2 or 2/3 that of
plasma.
 The K+ concentration rises to only 4times that of
plasma.

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Functions of saliva
 Mechanical Functions
Moistening action
Lubricating action:
Protective action:
Cleansing action
 Digestive Function
Starchy food is acted upon by ptyalin or salivary α
amylase
Maltase
 Excretory Functions
Salts of heavy metals - like lead, arsenic, bismuth,
iodide.
Viruses responsible for rabies (hydrophobia) and
anterior poliomyelitis.
 Solvent Function and Taste Sensations.
 Maintenance of Water Balance.
 Buffering Action.

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Regulation of salivary secretion
 Afferent path is formed by:
Branches of chorda tympani (which supply anterior
2/3 of tongue).
Glossopharyngeal nerve (which supply posterior 1/3 of
tongue).
Vagus.
Branches of trigeminal nerve.
Other sensory pathways - (olfaction, sight, hearing).

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Summary
 Introduction
 Salivary gland innervation.
 Composition
 Secretion
 Function
 Regulation of secretion.