salivary glands – anatomy and physiology
TRANSCRIPT
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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..