Lecture Handsout for students of 1st Year MBBS.

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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.