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SALIVA

DR NASRIN HABIB

MBBS,MPHIL(PHYSIOLOGY)

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Saliva

Saliva is a viscous, colourless,oplacent fluidwhich is secreted by three pairs of salivaryglands----the parotid,submandibular and

sublingual glands. There are also many smallbuccal glands from which salivation occurs.

Characters:

800-1500ml/day or1500ml/day. Slighlitly acidic.PH:6-7

Specific gravity:1.002-1.012

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Composition

Water:99.5% Solid:0.5%

Organic-O.3%

Enzyme:ptyline(salivary alpha-amylase),lingual lipse,corbonic

anhydrase phosphatase,lysozymes Other organics:Mucin,urea,cholesterol,amino acid.

Blood group subtances:Antigen of ABO blood group.

Inorganic(0.2%) NACL,KCL,acid and alkaline sodium

phosphate,calcium phosphate,CaCO3,KHC03 etc. Cellular Constituents: Yeast cell,bacteria,protozoa etc.

Gases:02,N2,C02.

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Function

Mechanical function:

keeps the mouth moist helps in speech.

Facilitates swallowing.

Helps in preparing food staffs into a bolus,suitable for digestion.

Dilutes hot and irritant food,thus prevents injuryto the mucosa

Acts as a lubricant. Washes down the food debris thereby prevent

bacterial growth.

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Function

Helps in taste by dissolving food stuff. Digestive function: It breaks down boiled starch into maltose in

presence of ptylin.Starch-Ptylin----Erythrodextrin---Achrodextrin-----Maltose.

Excretory function: It excretes urea, some heavymetals,thyocyanates,I2,penicillin.

Saliva helps in water balance: Saliva keeps the mouth moist, whenmoisture is reduced in the mouth, certain nerve ending at back ofthe tongue are stimulated the desire of thirst arises. The subjectthen take water thus water valance is maintained

Buffering function: due to presence of HCO3 and PO4 in saliva, itacts as buffer-NaHCO3,H2CO3 and Na2HPO4,NaH2PO4.

Bacteriolytic function: Cell membrane of bacteria containspolysaccharides,lysosome.The enzyme present in the saliva is apolysaccharide,thus it dissolves the cell membranes of manybacteria and finally kills them.

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Salivary Glands

3 pairs secrete into oral cavity

Each pair has distinctive cellular organization:

and produces saliva with different properties

Produce 1.01.5 liters of saliva each day:

submandibular gland: 70% by submandibular glands. Secrete both serous

and mucous type. The gland opens upon the floor ofthe mouth on the side of the frenulum of the tongue,

by duct of Wharton's duct.

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Salivary gland.Parotid gland

25% by parotids glands. Secrete mainly serous type,containing ptyelin.The gland opens upon the innersurface of the check, opposite the second uppermolar teeth, by duct of Stensen.

Sublingual gland

5% by sublingual glands-secrete both the serous andmucous types. The gland open by several fine

ducts, floor of the mouth on the frenulum of thetongue by duct of Rivinus.

There are small accessory buccal glands scatteredthroughout the mucous membrane and secrete

only mucous.

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Salivary gland

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Salivary glands

Nerve supply - Salivary glands are under the control of theautonomic nervous system-and receive efferent nerve fibersfrom both parasympathetic and sympathetic divisions(7th&9thcranial nerves)

Regulation of secretion-

1.Unconditional reflex-this is present since birth and is inborn(when any substance is put in the mouth)

2.Conditional reflex- That is by the sight, smell, hearing orthought of food. (Acquired-learnt after birth)

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Tractus solitarius &

salivation

Parasympathetic nervous regulation of

salivary secretion.

VII, IX & X cranial

nerves represent

parasympatheticdivision of ANS.

Secretomotor

functions.

From the tractus

solitarius, many taste

signals are

transmitted within the

brain stem itself

directly into

the super ior and

in fer ior sal ivatory

nucle i, and these areas transmit

signals to the

submandibular,

sublingual, and

parotid glands

to help control thesecretion of saliva

Taste Reflexes Integrated in the Brain Stem.

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Mechanism of saliva secretion

1)Neural control:Parasympathetic stimulation: superior and

inferior salivatory nuclei-causes--

vasodilatation-occurs and copious salivasecretion. Atropine and cholinergic blocking

agents reduce secretion. Acetylcholine

increase secretion.

Sympathetic stimulation: superior cervical

ganglioncauses vasoconstriction---

moderate amount of salivation.

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Mechanism..

2)Reflex:

Conditioned reflex: Here salivation occurs in presence of food

such as sight, vision and smell of food stimulate saliva

secretion reflexly although no food is actually given in mouth.

Unconditioned or inborn reflex: when food is actually given tothe mouth then the secretion of salivary gland occurs by

unconditioned reflex.

Salivation also occur in response to reflexes originating in the

stomach and upper intestines-particularly when veryirritating foods are swallowed or when a person is nauseated

because of some gastrointestinal abnormality. When a

person smells or eats favourite food ,salivation is greater than

when disliked food is smelled or eaten.

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Mechanism of saliva

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LEARING OUTCOME

1. Describe the mechanism for secretion of

saliva .

2.Explain the functions of each constituent of

the saliva.

3. State the functions of saliva.