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Salivary Glands – Anatomy and

PhysiologySaurabh Roy

11.11.15

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Overlay : Introducing Glands Salivary Glands Classifying Salivary glands Embryology of Salivary glands Anatomy and Clinical implications

Parotid Submandibular Sublingual Minor

Physiology and Clinical implications Conclusion References

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Introduction – What are Glands?: A cell, group of cells, or organ that selectively removes

materials from the blood, concentrates or alters them, and secretes them for further use in the body or for elimination from the body

Typically, a gland consists of either cuboidal or columnar epithelium resting on a basement membrane and is surrounded by a plexus, or meshwork, of blood vessels.

http://www.britannica.com/science/gland

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Types of Glands: Endocrine, or ductless, glands (e.g., pituitary, thyroid, adrenal)

secrete substances known as hormones directly into the bloodstream rather than through ducts.

Exocrine glands (e.g., salivary, sweat, digestive) discharge their products through ducts.

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Types of Exocrine glands : Exocrine glands.

Max sweat glands, Salivary glands, Lacrimal glands

Sweat glands around lips and

arm pitsSebaceous glands, Meibomian glands

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Types based on Ductal Pattern : Exocrine glands.

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Salivary Glands: Salivary glands are a group of exocrine, merocrine,

simple/compound tubulo-acinar type of glands secreting saliva The saliva forms a film of fluid coating the teeth and mucosa

thereby creating and regulating a healthy environment in the oral cavity

Oral fluid, which is referred to as mixed or whole saliva, includes the secretion of major glands, the minor glands, desquamated oral epithelial cells, microorganisms and their products, food debris and serum components and inflammatory cells that gain access through the gingival crevice

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Classifying Salivary Glands:

Based on size

Histochemical nature of fluid

Ductal system

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Classifying Salivary Glands: According to size :

Major salivary glands : Parotid, Submandibular , Sublingual Minor salivary glands : Carmalt’s glands, Glands of Von ebner

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Classifying Salivary Glands: According to nature of secretion:

Pure Serous – Parotid, Glands of Von Ebner Pure Mucous – Anterior lingual Glands of Blandin and

Nuhn Mixed – Submandibular and Sublingual

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Classifying Salivary Glands: According to ductal systems :

Simple – Minor Salivary glands Compound – Major Salivary glands

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Embryology:

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Embryology: The individual salivary glands arise as a proliferation of oral epithelial cells,

forming a focal thickening that grows into the underlying ectomesenchyme Continued growth results in the formation of a small bud connected to the

surface by a trailing cord of epithelial cells, with mesenchymal cells condensing around it

Formation of clefts occurs; forming 2 or more buds Continuation of this process, called Branching Morphogenesis produces

successive generations of buds and a hierarchic ramification of the gland Branching morphogenesis, defined as growth and branching of

epithelial tubules during embryogenesis, is a fundamental feature of renal, lung, mammary gland, submandibular gland, and pancreatic morphogenesis in mammals.

Hu MC, Rosenblum ND ;Genetic regulation of branching morphogenesis: lessons learned from loss-of-function phenotypes.Pediatric Res. 2003 Oct;54(4):433-8. Epub 2003 Aug 6.

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Embryology:

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Embryology:

The cells of secretory end pieces and ducts attain maturity during the last 2 months of gestation

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Microstructure of Glands:

Secretory units(Acini):• Serous cells• Mucous cells Myoepithelial

cells

Ductal units• Intercalated

ducts• Striated ducts• Excretory ducts

Connective Tissue:

Surrounding capsule

Tissue septaeTissue

elements

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Microstructure of Glands:

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Serous cells: Pyramidal with a broad base on the

basement membrane, apex facing the lumen

Secretory granules – Zymogen granules present in the apical cytoplasm

Abundance of RER Mature zymogen granules expelled

from the cell surface by exocytosis

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Mucous cells: Typically have a tubular configuration Mucous end pieces in some cases

have serous cells associated with them in the form of a demilune

The most prominent feature of mucous cells is the accumulation in the apical cytoplasm of their secretory product – mucus

Have a large Golgi complex, located basal to the mass of secretory granules

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Myoepithelial cells:

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Myoepithelial cells: Contractile elements associated with the secretory end pieces

and intercalated ducts Stellate shaped, numerous branching processes which envelop

the secretory end piece Fusiform shaped with fewer processes These processes are filled with actin and soluble myosin Contraction of these processes provides support to the end

pieces during active secretion of saliva Recent evidence also suggests that these cells provide signals to

acinar units to maintain cell polarity and structural organization of acini

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Ductal Elements: Acini

Intercalated ducts

Striated ducts

Excretory ducts

Stenson’s/ Wharton’s

ducts

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Ductal elements:• Single layer of cuboidal cells• Secretory units may also secrete lysozyme and

lactoferrinIntercalated

ducts:

• Constitute largest portion of ductal system; Columnar cells

• Modification of primary saliva by reabsorbtion and secretion of electrolytes

Striated ducts:

• Pseudostratified columnar epithelium• Other types of cells viz. Tuft cells, lymphocytes

and macrophages may be present within

Terminal Excretory

ducts:

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Anatomy and Clinical Implications :

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Parotid Gland : Largest serous salivary gland Weighs around 15 gms Resembles a 3 sided pyramid with apex directed downwards 4 surfaces:

Superior Superficial Anteromedial Posteromedial

Separated by 3 borders: Anterior Posterior Medial

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Parotid Capsule : Formed by Investing layer of deep

cervical fascia Fascia splits to enclose the gland Superficial lamina – Thick and

adherent is attached to the zygomatic arch

Deep lamina – Thin; attached to the styloid process, the angle & posterior border of ramus and tympanic plate

A portion of the deep lamina thickens to form the stylomandibular ligament which separates the parotid from the submandibular gland

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Parotid Gland - Relations :

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Parotid Gland - Relations: Superior Surface

Concave, Related to Cartilaginous part of ext acoustic meatus Post. Aspect of temperomandibular joint Auriculotemporal Nerve Sup. Temporal vessels

Apex Overlaps posterior belly of digastric and adjoining part of carotid triangle

Superficial Surface; Covered by Skin Superficial fascia containing facial branches of great auricular N Superficial parotid lymph nodes and post fibres of platysma

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Parotid Gland - Relations : Anteromedial Surface

Grooved by posterior border of ramus of mandible Related to

Masseter Lateral Surface of temperomandibular joint Medial pterygoid muscles Emerging branches of Facial N

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Parotid Gland - Relations : Posteromedial Surface is related to

Mastoid process with sternomastoid and posterior belly of digastric.

Styloid process with structures attached to it.

External Carotid Artery which enters the gland through the surface

Internal Carotid Artery which lies deep to styloid process

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Parotid Gland – Structures within: Arteries :

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Parotid Gland – Structures within: Veins:

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Parotid Gland – Structures within: Nerves:

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Patey’s Faciovenous plane: Large superficial and small deep part of the gland interconnected by an

isthmus Facial nerve divides along this plane

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Patey’s Faciovenous plane:- Clinical Significance The facial nerve must be traced from behind forwards as it emerges from

the stylomastoid foramen and enters the parotid gland The nerve is surrounded by a leash of veins called the neuro-venous plexus

of Patey which must be followed with fine dissection, preferably under a microscope, to surgically divide the isthmus.

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Parotid duct/Ductus parotideus/Stenson’s Duct: Thick walled and about 5 cm long Emerges from the middle of the anterior border of the gland Superior relations:

Accessory parotid Transverse facial vessels Upper Buccal branch of facial nerve

Inferior relations: Lower buccal branch of facial nerve

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Parotid duct/ ductus parotideus/ Stenson’s Duct: At the anterior border of the masseter,

the parotid duct turns medially and pierces: Buccal fat pad Buccopharyngeal fascia Buccinator

The duct runs forwards for a short distance between the buccinator and the oral mucosa.

Finally, the duct opens into the gingivobuccal vestibule opposite the crown of the maxillary 2nd molar tooth

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Parotid duct/ ductus parotideus/ Stenson’s Duct : Surface anatomy:

Corresponds to middle third of a line drawn from lower border of tragus to a point midway b/w nasal ala and upperlabial margin

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Parotid Gland – Blood Supply : Arterial supply: External carotid artery and its branches within

the gland Venous drainage: External & internal jugular vein

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Parotid Gland – Nerve Supply:

• Secretomotor• Reach through

auriculotemporal nerve

Parasympathetic

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Parotid Gland – Nerve Supply:

• Vasomotor • Derived from the plexus

around the middle meningeal artery

Sympathetic nerves

• Derived from the auriculotemporal nerve but the parotid fascia is innervated by the sensory fibres of Great Auricular nerve(C2,C3)

Sensory nerves

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Parotid Gland – Lymph Nodes: Lie partly in the superficial and partly in the deep fascia over the

parotid gland Drainage:

Temple Side of the scalp External acoustic meatus Middle ear Parotid gland Upper part of the cheek Parts of eyelids and orbit

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Anatomy – Clinical implications : Parotid swellings are extremely painful due to the unyielding

nature of parotid fascia – Acute Parotitis

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Anatomy – Clinical implications : A Parotid abscess may be caused by

spread of infection from the opening of parotid duct in the oral cavity

Else it may present as a slight swelling with redness on the surface of the swelling accompanied by acute, excruciating pain

It results from bacterial parotitis with the spread of pathogen in a retrograde manner

Does not show fluctuation due to unyielding nature of parotid capsule

Best drained by Horizontal incision known as Hilton’s Method below the angle of the mandible

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Anatomy – Clinical implications : Parotidectomy is the surgical removal of the parotid gland Injury to the auriculotemporal nerve can occur at a site where it

turns around the neck of the mandible Because of the injury, postganglionic parasympathetic fibres

from the Otic ganglion unite with sympathetic fibres of superior cervical ganglion which supplies vessels and sweat glands over skin overlying parotid region

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Anatomy – Clinical implications : This causes stimulation of the

sweat glands and hyperemia in its area of distribution, producing redness and sweating in the area of the skin supplied by the nerve

This clinical entity is called Frey’s Syndrome/Auriculotemporal Syndrome

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Anatomy – Clinical implications : Diagnosis : Minor’s Starch iodine test Prevention:

Physical barrier between the skin and parotid bed by using muscle flaps from temporalis or SCM

Treatment: Reassurance, aluminium chloride – antiperspirant(astringent) Denervation by tympanic neurectomy Injection of botulinum toxin into the affected skin

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Anatomy – Clinical implications : During parotidectomy, the facial nerve is preserved by removing

the gland in 2 parts, superficial and deep separately. Plane of cleavage is defined by tracing the nerve from behind

forwards

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Anatomy – Clinical implications : Swellings of parotid may either be due to inflammation or due to

tumours (benign or malignant) Since the gland is positioned below, behind and in front of the

lobule of the ear its swellings obliterate the normal hollow just below the lobule of the ear, which is invariably lifted in the parotid swellings

A painless slow growing tumour is usually benign in nature which does not damage the facial nerve

On the contrary, the malignant growth is characterized by rapidly growing painful swelling which involves the facial nerve producing facial palsy. Fixity with hardness and enlargement of cervical lymph nodes are other features

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Submandibular Gland : Location : Anterior part of Digastric

triangle Size of a walnut, roughly J-shaped

Superficial Part: Larger part, filling up the digastric triangle Extends up till the mylohyoid line It has inferior, medial and lateral surfaces Partially enclosed between 2 layers of

deep cervical fascia

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Submandibular Gland : Superficial Part: - Relations :

Inferiorly:Skin

PlatysmaCervical branch of facial nerve

Deep fasciaFacial vein

Submandibular Lymph Nodes

Medially:MylohyoidHyoglossusStyloglossus

Laterally:Submandibular fossa on the

mandibleInsertion of medial pterygoid

Facial Artery

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Submandibular Gland : Deep part: Small sized, lies deep to Mylohyoid, superficial to

hyoglossus and styloglossus Relations: Laterally:

Mylohyoid

Medially:Hyoglossus

Superiorly:Lingual nerve with

submandibular ganglion

Inferiorly:Hypoglossal Nerve

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Wharton’s Duct: Thin walled, about 5 cm long Emerges at the anterior end of the deep part of the gland Crossed by the lingual nerve at the region of anterior border of the

hyoglossus Opens on the floor of the mouth, on the summit of the sublingual

papilla, at the side of tongue frenulum

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Blood and Lymph Supply: Supplied by the facial artery Veins drain into the common facial or lingual vein Lymph passes into submandibular lymph nodes

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Nerve Supply:

Submandibular ganglion:

Secretomotor fibres

Vasomotor sympatheti

c fibres from facial

artery plexus

Sensory fibres from

lingual nerve

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Submandibular Gland – Clinical Implications: The chorda tympani supplying secretomotor fibres to

submandibular and sublingual glands lies medial to the spine of sphenoid

The auriculotemporal nerve supplying secretomotor fibres to parotid is related to the lateral aspect of the sphenoid

Injury to spine may involve both these nerves with loss of secretion from all 3 salivary glands

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Submandibular Gland – Clinical Implications:

Chronic Submandib

ular Sialadenitis

:

ObstructionTrauma to

floor of mouth

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Submandibular Gland – Clinical Implications: Sialadenitis due to calculi : Disease starts with acute

bacterial Sialadenitis which occurs secondary to obstruction

Submandibular gland has a poor capacity for recovery following obstruction

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Submandibular Gland – Clinical Implications: Sialadenitis due to calculi : Calculi are more common in the submandibular gland

because of the following reasons Higher mucin content Higher Calcium and phosphate content Non dependent drainage Kinking of Wharton’s duct

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Submandibular Gland – Clinical Implications: Sialadentis due to calculi : Clinical features:

Salivary colic Lingual colic H/O Enlargement of glands during meals Palpable calculi within the gland, the duct or the orifice Progression into severe septic Sialadentis mimicking Ludwig’s

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Submandibular Gland – Clinical Implications: Sialadentis due to calculi : Treatment:1. Stone in duct : removed by incising the mucosa over floor of

mouth and/or milking the stone, followed by a gush of blocked contents

2. Chronic Sialadentis : Excision of submandibular gland Complications :

Damage to lingual nerve, marginal mandibular nerve, hypoglossal nerve

Seroma and infection

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Sublingual Gland : Smallest of the 3 salivary

glands Almond-shaped and weighs 3-

4 g About 15 ducts emerge from

this gland Most open directly onto the

floor of the mouth while some join the submandibular duct

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Sublingual Gland : Blood supply: Lingual and submental

arteries

Nerve supply: Similar to submandibular

glandRelation

s:

Anteriorly:Meets with gland on

opposite side

Posteriorly:Contacts with deep part of

Submandibular Gland

Superiorly:Mucous

membrane of the mouth

Inferiorly:Mylohyoid

muscle

Laterally :Sublingual

fossa

Medially:Genioglossus

muscles

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Clinical Implications: Ranula :

Translucent cystic swelling with a bluish tinge situated on one side of frenulum linguae

Almost always unilateralPainless, slow growing ,soft, movable mass

located at the floor of the mouthWhen a ranula herniates through the

mylohyoid & extends into the neck so that it can be palpable in the submandibular triangle, its called a Plunging Ranula

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Minor Salivary Glands: They are located beneath the oral epithelium in almost all parts of the

oral cavity except in the gingiva, ant. Hard palate and ant. 2/3rd of tongue dorsum

600 – 1000 in number present in small clusters of secretory units Classified according to their anatomic location Continuous slow secretory activity Often supersede the activity of major salivary glands at night

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Minor Salivary Glands: Glands of Blandin and Nuhn

Mostly Located near apex of tongue, some also found posteriorly

Chiefly mucous Anterior glands open on ventral surface near lingual frenum Posterior glands open on tongue dorsum

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Minor Salivary Glands: Glands of Von ebner

Located on posterior aspect of tongue

Exclusively serous Functions:

Washout of trough papillae Readying taste receptors for a new

stimulus Antibacterial activity (lysozyme and

peroxidase) Lipolytic activity (lingual lipase)

with significant activity in newborn when pancreatic lipase activity is low

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Clinical Implications : Mucocoele : Clinical term that describes swelling

caused by accumulation of saliva at the site of a traumatized or obstructed salivary duct

Extravasation mucocoeles most commonly occur on the lower lip,buccal mucosa, tongue and floor of the mouth

Retention mucocoeles commonly occur on the palate

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Clinical Implications: Minor Salivary gland tumour : They can present either as a mucous

retention cyst or as malignant tumour Since they are submucosal, they start

as a submucosal nodule whuch helps them to differentiate from carcinoma lip/buccal mucosa etc

Presence of an ulcer may be a feature of malignancy

Treatment of benign cyst/tumour is by simple excision while malignant tumours require wide excision

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Physiology of Salivary Secretion

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Physiology of Salivary Secretion : Production – 1l/day (0.1 – 4 ml/min) varying from rest to stimulation

Constituents:

Water 94-99.5%

Solids – 0.5-6%

Inorganic Organic

Organic micromolecul

es

Gases

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Functions of Saliva: Lubrication and protection Buffering and clearance Maintenance of tooth integrity Antibacterial activity Taste and digestion Excretion of certain drugs and inorganic ions

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Mechanism of Salivary Secretion : Mechanism of Salivary

Secretion: Active transport process

under neuronal control Osmotic process

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Mechanism of Salivary Secretion :1. Acinar cells: K, Na and HCO3 ions along with Cl to preserve

neutrality Primary secretion – Isotonic Ductal cells(rich blood supply) –

Reabsorption of Na ions Secretion of HCO3 and K ions

Final salivary secretion - Hypotonic

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Mechanism of Salivary Secretion :2. Since saliva is a hypo-osmotic secretion of salivary glands Hence, metabolic activity i.e. Oxygen consumption is increased

by 5 folds during secretory activity as compared to that at rest

3. At rest, Saliva contains more K ions, less of Na, Cl and Bicarbonate ions compared to plasma

However, as salivary flow increases, there is less time for ion exchange in the ducts, the result being less hypotonic and more isotonic resembling primary secretion

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Mechanism of Salivary Secretion :4. Aldosterone increases the K concentration and decreases the Na

concentration of saliva Thus, a high salivary Na/K ratio is seen when aldosterone is

deficient

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Control of Salivary Secretion :1. Stimulation of parasympathetic nerves:

Liberates Kallikrein from the gland cells which acts on plasma globulins to form bradykinin

Effect mediated by release of Ach Also causes release of Vasoactive Intestinal Polypeptide Thus ,the effects being:

Vasodilatation in salivary glands Increased secretion from the acini

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Control of Salivary Secretion :2. Stimulation of sympathetic nerves:

Shorter and less strong Probable synergistic action Causes secretion of small amounts of saliva rich in organic

constituents and mucus from submandibular and sublingual glands3. Salivary secretion increases either by :

Taste of food within 20-30 seconds (Innate reflex) By sight ,smell or thought of food (Conditioned reflex)

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Factors altering Salivary Flow: Unstimulated – Submandibular

Stimulated – Parotid 2/3rd

Acidic food – Max stimulation

Sweet food – Least stimulation

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Factors altering Salivary Flow: Psychic factors Circadian rhythm Diurnal variation Age Drugs

Tricyclic antidepressants Phenothiazines

Depression and anxiety states Dehydration, hemorrhage

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Factors altering Salivary Flow: Salivary Gland diseases

Radiation sialadenitis

Autoimmune sialadenitis

HIV infection

Iron overload

Sarcoidosis

Amyloidosis

Cystic fibrosis

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Effect of Drugs on Salivary Flow: Sympathomimetic drugs like adrenaline and ephedrine stimulate

salivary secretion Parasympathomimetic drugs like Ach, pilocarpine, muscarine and

physostigmine increase the secretion of saliva Histamine stimulates salivary secretion Sympathetic depressants like ergotamine and dipheniramine abolish

salivary secretion Parasympathetic depressants like atropine and scopolamine inhibit the

secretion of saliva Anaesthetics like chloroform and ether stimulate the reflex secretion of

saliva However, deep anaesthesia decreases salivary secretion due to central

inhibition

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Factors altering Salivary composition: Flow rate Source of secretion Type of stimulus Diurnal variation Diet Drugs – flow dependant components Hormones – mineralocorticoids, ovulation

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Factors altering Salivary composition: Disease states

Sialadenitis Radiation damage Sjorgen’s syndrome Cystic fibrosis HTN DM Alcoholic cirrhosis Aldosteronism Chronic pancreatitis

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Applied Physiology:1. Hyposalivation :

Reduction in salivary secretion 2 types, temporary and permanent

Temporary – Emotional conditions like fear, Fever, or Dehydration Permanent

Sialolithiasis Congenital absence or hypoplasia of salivary glands Bell’s palsy

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Applied Physiology:2. Xerostomia : Dry mouth/Pasties/Cottonmouth Due to hyposalivation or aptyalism Causes :

1. Dehydration due to Renal failure2. Sjogren’s syndrome3. Post Radiotherapy4. Trauma to gland or ducts5. Side effect of some drugs6. Shock7. After smoking marijuana

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Applied Physiology:3. Hypersalivation: Excess secretion of saliva Physiological condition – Pregnancy Pathological hypersalivation is called Ptyalism, Sialorrhoea, Sialism or

Sialosis Occurs in following conditions :

Tooth decay or neoplasm of mouth or tongue Disease of oesophagus, stomach or intestine Neurological disorders like cerebral palsy and mental retardation Cerebral Stroke Parkinsonism Nausea and vomiting

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Applied Physiology:4. Drooling : Uncontrolled flow of saliva with inability to retain saliva in the

mouth Occurs in following conditions :

During teeth eruption in children Upper respiratory tract infection or nasal allergies in children Dysphagia Tonsillitis Peritonsillar abscess

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Applied Physiology:5. Paralytic secretion of Saliva : Iatrogenic/Traumatic severance of parasympathetic nerve supply Leads to increase in salivary secretion for 3 weeks, later it

diminishes finally stopping at about 6th week The increased secretion of saliva after cutting the PS nerve fibres

is called Paralytic secretion It is due to the release of large amounts of adrenaline from

adrenal medulla after denervation Cutting of the sympathetic Nerve supply does not influence

paralytic secretion

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Applied Physiology:

6. Augmented Secretion of Saliva: If the nerves supplying salivary glands are stimulated twice, the

amount of saliva secreted by the 2nd stimulus is more than due to the 1st stimulus

It is because, the 1st stimulus increases excitability of acinar cells, so that when the 2nd stimulus is applied, the salivary secretion is augmented

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Conclusion: Knowledge of anatomy and physiology of salivary glands

is essential to distinctly identify various associated conditions and salivary gland pathologies

Precise anatomical knowledge is also essential to plan out our treatment strategies and alter the patient’s lifestyle for the better

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References: Inderbir Singh; Human Embryology; 10th edition; 96,178 Moore, Persaud, Torchia ; The Developing Human; 9th edition; 179 Inderbir Singh; Textbook of Anatomy; 5th edition Volume 3; 781 B D Chaurasia; Human Anatomy; 6th edition Volume 3; 106-112 , 133-8 K Sembulingam; Essentials of Medical Physiology; 4th edition; 197-203 A K Jain ; Textbook of Physiology; 4th edition Volume 1; 201-4 Antonio Nanci; Tencate’s Oral Histology; 8th edition; 253-71 G S Kumar; Orban’s Oral Histology and Embryology; 13th edition, 291-306 Somen Das; A manual on clinical surgery; 8th edition; 359-63 K Rajgopal Shenoy; Manipal Manual of Surgery; 4th edition; 302-8 http://www.britannica.com/science/gland http://www.ncbi.nlm.nih.gov/pubmed/12904600 https://shortnotesinplasticsurgery.wordpress.com/2013/12/17/40-surgery-of-the-pa

rotid-gland/ http://www.google.com/images

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Thank you and Good day..