INTRODUCTION

SALIVARY GLANDS are defined as compound, tubuloacinar, merocrine, exocrine glands whose ducts open into the oral cavity. Compound: refers to the fact that salivary gland has more than one tubule entering the main duct. Tubuloacinar: describes the morphology of the secreting cells. Merocrine: indicates that only the secretion of the cell is released and not the cytoplasm. Salivary glands are complex networks of hollow tubes and secretory units that are found in specific locations of the mouth and which, although architecturally similar, exhibit individual specificities according to their location. Saliva serves multiple and important functions. Three major, paired salivary glands produce the majority of saliva: the parotid, the submandibular, and the sublingual glands. In addition, 600-1,000 minor salivary glands line the oral cavity and oropharynx, contributing a small portion of total salivary production.

CLASSIFICATIONS

1) The salivary glands in humans are mainly divided into

[A] Paired Major glands

Parotid

Submandibular

Sublingual

[B] Minor salivary glands distributed throughout oral cavity .

2) It can be further classified on mode of secretion as;

[A] Exocrine gland secretions are carried away by duct.

All Major salivary glands

[B] Mesocriine gland in which secretory products pass through the cell wall.

All Minor salivary glands

3) It can be classified on the basis of nature of secretion;

[A] Serous [thin watery secretion] - Parotid

[B] Mucus [Thick viscous substance] - Submandibular

[C] Seromucus [combination] - Sublingual

EMBRYOLOGY

The major salivary glands develop from the 6th- 8th weeks of gestation as outpunching of oral ectoderm into the surrounding mesenchyme. The parotid enlarge develops first, growing in a posterior direction as the facial nerve advances anteriorly; eventually, the fully developed parotid surrounds CN VII. However, the Parotid gland is the last to become encapsulated, after the lymphatics develop, resulting in its unique anatomy with entrapment of lymphatics in the parenchyma of the gland.

The epithelial buds of each gland enlarge, elongate and branch initially forming solid structures. Branching of the glandular mass produces arborization. Each branch terminates in one or two solid end bulbs. Elongation of the end bulb follows and lumina appears in their centers, transforming the end bulbs into terminal tubules. These tubules join the canalizing ducts to the peripheral acini. Canalization results from mitotic activity of the outer layers of the cord outpacing that of the inner cell layers. Canalization is complete by 6th month post conception.

The minor salivary glands arise from oral ectoderm and nasopharyngeal endoderm. They develop after the major salivary glands.

ANATOMY

Major Salivary Glands

Parotid Gland –

The parotid gland represents the largest salivary gland, averaging 5.8 cm in the craniocaudal dimension, and 3.4 cm in the ventral-dorsal dimension. The average weight of a Parotid gland is 14.28 g. It is irregular, wedge shaped, and unilobular. The Parotid has been described as having 5 processes (3 superficial and 2 deep), It lies in the parotid compartment, a triangular space which also contains CN VII and its branches, sensory and autonomic nerves, the External Carotid artery and its branches, the Retromandibular (Posterior Facial) vein, and Parotid lymphatics. Relations of various structures to the parotid gland are as follows-

Above- lies external auditory meatus and temporomandibular jointBelow- it overflows the posterior bell of digastricsAnteriorly- it overflows the mandible with overlying masseterMedially- lies the styloid process and its muscles separating the parotid from internal juglar vein, internal carotid artery,last four cranial nerves and lateral wall of the pharynx.

Most important of these is the facial nerve, the branches of which emerge at the anterior, upper and lower borders of gland. The facial nerve enters the deep surface of the gland as a single stem, passing posterolateral to the styloid process as it does so. Within the substance of gland it may first divide into two stems, or it may rebranch and anastomose to form a parotid plexus. The facial nerve usually leaves the shelter of the gland as five or more branches. In its course through

the parotid gland, facial nerve runs superficial to those chief blood vessels that traverse the gland, but is interwoven with the glandular tissue and its ducts.Nervous supply – parasympathetic supply is through auriculotemporal nerve,sympathetic supply is derieved from plexus around the external carotid artery and sensory supply is through auriculotemporal nerve and great auricular nerve.Arterial supply is provided by the Transverse Facial artery from the Superficial Temporal artery, providing blood to the Parotid gland, Stensen’s duct, and the Masseter muscle. This artery runs between the zygomatic arch and Stensen’s duct.Venous drainage is provided by the Retromandibular vein, which lies deep to the Facial nerve. This vein runs lateral to the Carotid artery, and emerges at the inferior pole of the Parotid gland.Lymphatic drainage is unique in the Parotid with Paraparotid and Intraparotid nodes. The Paraparotid nodes are more numerous and drain the temporal region, scalp, and auricle. The Intraparotid nodes drain the posterior nasopharynx, soft palate, and ear. The Parotid lymphatics drain into the superficial and deep cervical lymph nodes.The parotid duct(Stenson duct) is 5cm long. It arises from anterior part of gland, runs over the masseter a finger breadth below the zygomatic arch to pierce the buccinators and open opposite the second upper molar tooth.

Submandibular Gland

It is situated in anterior part of the digastrics triangle, formed by the anterior and posterior bellies of the Digastric muscle and the inferior margin of the mandible.Iis roughly J-shaped being indented by posterior border of the mylohyoid which divides it into a larger part superficial to the muscle, and a small part lying deep to the muscle. The Submandibular gland is invested in its own capsule, which is also continuous with the superficial layer of deep cervical fascia.It is supplied by facial artery. The veins drain into the common facial or lingual vein.Lymph passes to submandibular lymph nodes.Nervous supply is from the branches of submandibular ganglion.The submandibular duct(wharton’s duct) is thin walled and about 5 cm long. It emerges at the anterior end of the deep part of the gland and runs forwards on the hyoglossus, between the lingual and hypoglossal nerves.At the anterior border of hyoglossus, the duct is crossed by lingual nerve.It opens on the floor of mouth, on the summit of the sublingual papilla, at the side of frenulum of the tongue.

Sublingual Gland

This is the smallest of the major salivary glands. The almond shaped gland lies just deep to the floor of mouth mucosa between the mandible and Genioglossus muscle. It is bounded inferiorly by the Mylohyoid muscle. Wharton’s duct and the Lingual nerve pass between the Sublingual gland and Genioglossus muscle. It has no true fascial capsule.

The gland receives its blood supply from the lingual and submental arteries. The nerve supply is similar to that of submandibular gland.

Unlike the Parotid and Submandibular glands, the Sublingual gland lacks a single dominant duct. Instead, it is drained by approximately 10 small ducts (the Ducts of Rivinus), which exit the superior aspect of the gland and open along the Sublingual fold on the floor of mouth. Lymphatic drainage goes to the Submandibular nodes.

Minor Salivary Glands

These are located beneath the epithelium in almost all parts of oral cavity.These glands usually consist of several small groups of secretory units opening via short ducts directly into the mouth.They lack a distinct capsule, instead mixing with the connective tissue of submucosa or muscle fibers of tongue or cheek.It consists of labial and buccal glands,glossopalatine glands, palatine glands, weber glands(superior pole of tonsils), von-ebner glands(base of tongue) and lingual glands.

Most of the minor glands receive parasympathetic innervation from the Lingual nerve, except for the minor glands of the palate, which receive their parasympathetic fibers from the Palatine nerves, fed by the Sphenopalatine ganglion.

HISTOLOGY

The secretory unit (salivary unit) consists of the acinus, myoepithelial cells, the intercalated duct, the striated duct, and the excretory duct. All salivary acinar cells contain secretory granules; in serous glands, these granules contain amylase, and in mucous glands, these granules contain mucin. Acini, responsible for producing the primary secretion, are divided into 3 types:

1) Serous (protein-secreting)=spherical cells rich in zymogen granules 2) Mucous (mucin-secreting)=more tubular shaped cells; mucinogen granules are washed out on H&E preparations giving an empty cell appearance 3) Mixed=serous demilunes, or predominantly mucous acinar cells capped by a few serous acinar cells Myoepithelial cells send numerous processes around the acini and proximal ductal system (intercalated duct), moving secretions toward the excretory duct.

Mucous cells – They contain large translucent mucinogen granules consisting of precursor of mucin and appear pale or translucent. It forms a viscous secretion containing mucin, a useful lubricant for food and oral mucosa.

Serous cells – They contain opaque small zymogen granules consisting of a precursor of ptyalin. It forms a thin watery secretion containing “ptyalin”which initiates digestion of starch to maltose.

The Parotid gland is a purely serous salivary gland. Of note, the Parotid gland is unique in that it contains many fat cells; in fact, the adipocyte to acinar cell ratio in the Parotid is 1:1. The Submandibular gland is mixed, but predominantly serous. Approximately 10% of its acini are mucinous. The Sublingual gland is mixed, but predominantly mucous. Of the major salivary glands.

SALIVA

"Saliva is a clean, tasteless, odorless slightly acidic viscous fluid, consisting of secretions from the parotid, sublingual, submandibular salivary glands and mucous glands of oral cavity".

Composition – Mixed saliva contains 99.5% water and 0.5% solids.Solids are organic substances and inorganic substances. Apart from these, gases are also found in saliva.

Organic substances- salivary proteins- mucin and albumin; salivary enzymes- amylase, maltase, lysozyme, phosphatase and carbonic anhydrase; kallikirin, enzyme necessary for bradykinin production; blood group components- antigens, free amino acids, non protein nitrogenous substances like urea, uric acid, creatinineand hypoxanthine.

Inorganic substances- sodium, calcium, potassium, bicarbonate, bromide, chloride, fluoride and phosphate.

Gases- oxygen, carbon dioxide and nitrogen.

Properties Of Saliva-

It is also called as “liquid enamel” as it is a rich source of various minerals

Total amount : 1200 - 1500 ml in 24 hours. A large proportion of this volume is secreted at meal time when the secretory rate is highest.

Consistency : Slightly cloudy because of the presence of cells and mucin.

Reaction : Usually acidic pH (6.02 - 7.05)

Specific gravity : 1.002 to 1.02

Function of Saliva --At least 8 major functions of saliva have been identified :

1) Moistens oral mucosa. In fact, the mucin layer on the oral mucosa is thought to be the most important nonimmune defense mechanism in the oral cavity.

2) Moistens dry food and cools hot food. 3) Provides a medium for dissolved foods to stimulate the taste buds. 4) Buffers oral cavity contents. Saliva has a high concentration of bicarbonate ions. 5) Digestion. Alpha-amylase, contained in saliva, breaks 1-4 glycoside bonds, while lingual lipase helps break down fats. 6) Controls bacterial flora of the oral cavity. 7) Mineralization of new teeth and repair of precarious enamel lesions. Saliva is high in calcium and phosphate.

8) Protects the teeth by forming a “Protective Pellicle”. This signifies a saliva protein coat on the teeth which contains antibacterial compounds. Thus, problems with the salivary glands generally result in rampant dental caries.

Mechanism of salivary secretion

The acinar cells secrete k+ & HCO3by active process into the acinar lumen, accompanied by sufficient Chloride ion to preserve electrical neutrality; simultaneous passage of water into the acinar lumen makes the primary secretion isotonic.The salivary duct cells which drain the acini have a rich blood supply, therefore, they actively reabsorb Na+ and accompanying chloride anion and transfer some k+ and HCO3 into salica.The duct cells being relatively impermeable to water makes final salivary secretion hypotonic.At rest, saliva contains more k+ and less of Na,chloride and HCO3 compared to their plasma concenterations. As salivary flow increases, there is less time for ion exchangein the ducts, as result saliva becomes less hypotonic. As a result of this,pH of saliva which is < 7 at low secretory rates increases to approx 8 as the rate of salivary secretion increases.

Regulation of salivary secretion

Stimulation of parasympathetic nerves, liberate proteolytic enzyme kallikrein from gland cells,which act on alpha2 globulins to form bradykinin. The effect is mediated by release of acetylcholine.. This produces- vasodilatation of blood vessels of salivary glands and stimulates secretion from acini. Therefore it causes profuse secretion of watery saliva.Stimulation of sympathetic nerve supply causes secretion of small amounts of of saliva rich in organic contents and mucous from submandibular and sublingual glands.

Saliva as diagnostic fluidThe use of saliva as a diagnostic fluid is a relatively recent trend. This is not surprising when oneconsiders its many advantages and the fact that saliva contains a wide array of constituents.1Saliva collection is non-invasive compared with phlebotomy, and, as a result, more acceptable topatients. As obtaining saliva is easy, self-collection after instruction is possible and there is no need for trained staff. Moreover, it does not carry the risk of needle-stick injuries. Saliva collection is also less likely to cause stress compared with other invasive procedures such as phlebotomy, an important consideration when researching biomarkers of stress. Lastly, saliva samples can reflect real-time levels of biomarkers, unlike other biological fluids, such as urine, which is stored in the bladder for a few hours before sampling.A wide range of biomarkers is measurable in saliva, including heavy metals (eg, lead), hormones (eg, cortisol, dehydroxyepiandrosterone (DHEA)), toxins and their metabolites (eg, cotinine), enzymes (eg, lysozyme, a-amylase), immunoglobulins (eg, IgA), other proteins (eg, eosinophil cationic protein) and DNA. Researchers are also studying the proteomic components of saliva in the hope of identifying novel biomarkers of disease. Role of saliva in dental caries

Salivary Clearance from the Oral Cavity-One of the most important role of saliva with respect to caries is in removal of bacteria and food debris from mouth.

Bacteria:When the saliva is swallowed, any bacteria contained are removed from the oral cavity and pass into the stomach. The average unstimulated saliva flow rate is about 0.3ml/min and the amount of saliva prior to swallowing is of the order of 3 or 4 times that volume. Thus the half life in the oral cavity for the inert material suspended in saliva is only a few minutes and is certainly less than the mean generation time of the oral micro-organisms.

DebrisWhen the food debris is retained in the mouth it remains available as a substrate for the metabolic activity of the oral micro-organisms. Thus if clearance of food debris is retarded from any reason, this will tend to promote the development of dental caries.

The Acquired Salivary PellicleA thoroughly cleaned tooth will, within seconds of exposure to saliva, acquired an amorphous, proteinaceous membrane called the acquired pellicle which originates from the absorption of several salivary proteins upon the hydroxyapatite surface of enamel This is of general clinical relevance as, following the acid-etch procedure, it is essential to prevent contact of etched enamel with saliva prior to placement of composite resin, otherwise the salivary protein will tend to fill up the defects in the newly etched surface. The pellicle thickness varies about 100 nm after 2 hrs to about 400 nm after 28 hrs.Properties and function of pellicle includes-It acts as a lubricant to prevent premature wear of enamel during mastication It reduces the rate of demineralization of tooth surface by acidic foods and drinks It acts as a semi permeable membrane and reduces ion mobility. This property is probably important in prevention of initial cavitation

Salivary gland Disorders

Classification—

DEVELOPMENTAL• Aberrancy• Aplasia & Hypoplasia• Atresia• Accessory ducts• Congenital Fistula

OBSTRUCTIVE• Sialolithiasis• Mucus Plugs• Stricture and Stenosis• Foreign bodies• Extraductal causes

INFECTION• Viral• Bacterial• Mycotic

AUTOIMMUNE DISORDER• Sjogren syndrome• Mikulicz’s disease• Uveparotid fever• Recurrent nonspecific parotitis

CYSTIC• Mucocele• Ranula

NEOPLASMS• [A-1] Benign • [Non recurrent]• Warthin’s tumor• Oncocytoma• Monomorphic adenoma• [A-2] Benign • [Recurrent]• Pleomorphic adenoma• Mucoeperdmoid tumor• Acinic cell tumor• [B] Malignant • CA in adenoma• Adenoid cystic CA• Muco epidermoid tumor• Acinic cell tumor• Adenocarcinoma• Undifferentiated CA

ASYMPTOMATIC ENLARGEMENT• Sialosis• Allergic• Malnutrition• Alcoholism

FUNCTIONAL DISORDERS• Xerostomia• Sialorrhoea

Aplasia Any one or group of salivary glands may be absent unilaterally or bilaterally. Aplasia becomes manifest with development of xerostomia and its sequale.It is sometimes associated with Treacher Collin syndrome or hemifacial microsomia.

Aberrancy It is the situation in which these glands are found farther than norml from their usual location.

MumpsMumps is due a paramyxovirus (the mumps virus) and causes painful swelling of the parotids and sometimes other glands. It is highly infectious and is the most common cause of acute parotid swelling. Children are mainly affected. An incubation period of about 21 days is followed by headache, malaise, fever and tense, painful and tender swelling of the parotids. Permanent nerve deafness or, rarely, meningitis are possible complications. mumps may be mistaken for a dental infection or bacterial sialadenitis, if unilateral. Rarely, when the submaxillary or sublingual glands are affected, mumps may have to be differentiated from lymphadenitis.Virus can be isolated from saliva and throat swabs two days before or seven days after onset of parotitis.

Xerostomia

It is not a disease but can be a symptom of certain diseases.It can produce serious negative effects on the patient’s quality of life, affecting dietary habits, nutritional status, speech, taste, tolerance to dental prosthesis, and increased susceptibility to dental caries. The causes of xerostomia can be salivary duct calculi, sialodentis, drug therapy, salivary gland aplasia and sjogren syndrome. Unilateral dryness with pain or discomfort and swelling in the affected gland on stimulation is often an indication of duct calculus.Sjogren syndrome commonly produces bilateral swellings, often constant and accompanied by other symptoms of syndrome. When the deficiency of saliva is pronounced, there may be severe alterations in the mucous membranes, and the patient may have extreme discomfort.

Mucoceles and cystsThe most common type of salivary and soft-tissue cyst is the extravasation mucocele of minor glands. It is not a true cyst as it has no epithelial lining. Retention cysts are far less common. Mucoceles mainly affect the minor salivary glands, particularly of the lip. The cause is usually damage to the duct of a mucous gland. Mucoceles most often form in the lower lip but occasionally on the buccal mucosa or floor of the mouth (ranula). They are usually superficial and rarely larger than 1 cm in diameter. In the early stages they appear as rounded fleshy swellings. Later, they are obviously cystic, hemispherical, fluctuant and bluish due to the thin wall.

RanulaA ranula is an uncommon type of salivary cyst arising from the sublingual or submandibular salivary glands. The structure is usually the same as other salivary retention cysts. Ranulae are usually unilateral and 2 or 3 cm in diameter. Occasionally they extend across the whole of the floor of the mouth. They are soft, fluctuant and bluish. They are typically painless but may interfere with speech or mastication.

SialolithiasisIt is the occurrence of calcareous concretions in salivary ducts of glands. They form by deposition of calcium salts around central nidus, which may consist of desquamated epithelial cells, bacteria, foreign bodies, or products of bacterial decomposition. The cause is unclear, but their formation may be promoted by chronic sialadenitis and partial obstruction.The occlusion of duct prevents the free flow of saliva and this stagnation or accumulation of saliva nder pressure produces pain and swelling. They are most commonly associated with submandibular gland and duct.

Pleomorphic adenomaPleomorphic adenomas ('mixed tumours') account for about 75% of parotid tumours but a lower proportion of intraoral salivary gland tumours. They arise mainly from duct epithelium or myoepithelial cells. These varied tissues are completely disordered in arrangement and the proportions of the different components also vary widely. Growth of pleomorphic adenomas is slow and may take several years to reach an inch in diameter. They form rubbery, often lobulated swellings . When close under the mucosa, the tumour may appear bluish. The swelling is typically attached to the overlying mucosa but mobile on the deeper tissues. Treatment is by wide excision: recurrence is otherwise inevitable. The reputation of the pleomorphic adenoma for recurrence is due to the great surgical difficulties of complete removal of tumours from the parotid (the common site), where the facial nerve, in particular, makes dissection hazardous

Worthin's tumour (adenolymphoma)I O Warthin's tumour arises in the parotid glands and accounts for about 9% of tumours there. It has a highly characteristic histological appearance consisting of tall, eosinophilic columnar cells which form a much-folded layer covering dense lymphoid tissue, including many germinal centres (Fig. 18.25). These structures line and form papillary projections into cystic spaces Warthin's tumour is benign and responds to enucleation but is sometimes multiple.

Mucoepidermoid CarcinomaMost common parotid malign tumor (15% of the parotid tumors) and the second most frequent in submandibular gland (2). It’s histologically composed by 2 types of cells, the mucous and the epidermoid cells, and from this differentiation they may be divided into low, intermediate and high grade, based on the prevalence of one or another. The tumoral level is one of the most important prognostic factors in 5 years: 92-100% in those of low grade, 62-92% in intermediate grade and 0-43% in high grade. Low grade tumors are composed by several mucous cells and cystic spaces (2). Most of them occur between the 4th and the 6th decades generally with a

record of low growth in months or years, with slight feminine predominance and in +7% of the cases the patients have peripheral facial paralysis to diagnosis. The high grade tumors are quite similar to the squamous cells carcinoma and in some cases require a more specific pathologic evaluation.

Cystic Adenoid CarcinomaThe second most common salivary glands malign tumor and corresponds to 10% of the neoplasms. There’s no predominance as to sex and race and the diagnosis average age is about 45 years. Macroscopically it generally represents inadequately encapsulated, infiltrative and pink-grey small lesions Perineural invasion is a typical statement of such neoplasm And it composes the most painful neoplasm of the salivary glands.

SJOGREN'S SYNDROMEIn 1933 Sjogren noticed the association of dryness of the mouth and dryness of the eyes. Later he found that there was a significant association with rheumatoid arthritis. These combinations of complaints are caused by two closely related but distinct diseases. Primary Sjogren's syndrome comprises dry mouth and dry eyes not associated with any connective tissue disease. Secondary Sjogren's syndrome comprises dry mouth and dry eyes associated with rheumatoid arthritis or other connective tissue disease. Primary Sjogren's syndrome tends to cause more severe oral and ocular changes and has a higher risk of lymphomatous change than secondary. Sjogren's syndrome is an autoimmune (connective tissue) disease which shows a corresponding variety of immunological abnormalities. In the early stages, the mucosa may appear moist but salivary\ flow measurement shows diminished secretion. In established cases the oral mucosa is obviously dry, often red, shiny and parchment-like (Fig. 18.10). The tongue is typically red, the papillae characteristically atrophy and the dorsum becomes lobulated with a cobblestone appearance. With diminished salivary secretion the oral flora changes and candidal infections are common.

DIAGNOSTIC TOOLS FOR SALIVARY GLANDS

The methods employed are:Plain Film RadiographyIntraOral RadiographyExtraOral Radiography

Sialography Computed Tomography (CT)Magnetic Resonance Imaging Scintigraphy UltraSonography

Sialography – It is the radiographic visualization of salivary gland following retrograde instillation of soluble contrast material in to the ducts. It is the recommended methods for evaluating intrinsic and acquired abnormalities of the ductal system because it provides the clearest visualization of branching ducts and acinar endpieces. Salivary obstruction, weather by sialolith or stricture, can be easily recognized by sialography. The two contraindications to sialography are acute infections, and allergy to contrast media.

Conclusion

A deep knowledge of the anatomy and physiology of such glands is required for a suitable clinical and surgical approach. Since several factors can influence salivary secretion and composition a precise standard for saliva collection must be established. Such a standard would make the test results obtained through sialometry and/or sialochemistry more helpful in characterizing the true functional state of the salivary glands which in turn would serve as indicators for a diagnosis when oral and/or systemic alterations are suspected.

Refrences

1) Hollinshed’s Textbook of Anatomy, Cornlius Rosse,,P.G. Rosse, 5th Edition2) Clinical Anatomy,Harold Ellis,9th Edition3) Principles of Anatomy & Physiology,Gerard J. Tortora,Bryan Denickson4) Shafer’s Textbook of Oral Pathology,5TH Edition5) Burket’s Oral Medicine Diagnosis and Treatment,Greenberg, Glick,Tenth Edition6) Understanding Dental Caries,Volume 1,Nikiforuk7) Human Physiology for Dental Students,A.K. Jain,3rd Edition8) Orban’s Oral Histology and Embryology,11th Edition9) B D Chaurasia’s Human Anatomy,Volume 3,fourth Edition10) Anatomy and Physiology of Salivary Glands , Frederick S. Rosen, MD, Grand Rounds

Presentation, UTMB, Dept. of Otolaryngology11) The use of Salivary Biomarkers in Occupational and Emviormental Medicine,

David Soo-Quee Koh, Gerald Choon-Huat Koh, Occup Environ Med 2007;64:202–210. 12) Cawson’s Essentials of Oral pathology and Oral Medicine,R.A Cawson,E.W. Odell13) Saliva Composition and Functions: A Comprehensive Review,Patrica Del Vigna de

Almeda,Journal of contemporary Dental Practice,Volume 9,200814) Salivary Glands Neoplasms, Allex Itar Ogawa, Lucio Eidy Takemoto, Paulo de Lima

Navarro, Rosana Emiko Heshiki

SALIVARY GLANDS

CONTENTS

INTRODUCTION

CLASSIFICATIONS

EMBRYOLOGY

ANATOMY

SALIVA

SALIVARY GLAND DISORDERS

DIAGNOSTIC TOOLS FOR SALIVARY GLANDS

CONCLUSION

REFRENCES