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1. IntroDuction
The salivary glands in mammals are exocrine glands that produce
saliva through a system of ducts. Humans have three paired major
salivary glands (parotid, submandibular, and sublingual) as well as
hundreds of minor salivary glands.
Salivary glands can be classifiedas serous, mucous or seromucous
(mixed).
In serous secretions,the main type of protein secretedis
ptyalin(alpha-amylase), anenzyme that breaks down starchinto
maltose and glucose,whereas in mucous secretions, the main protein
secretedis mucin which acts as a lubricant.
In health, between0.5 and 1.5 litres of saliva are produced every day.
The secretionofsaliva (salivation)is mediated by parasympathetic
stimulation; acetylcholine is the active neurotransmitter and binds to
muscarinic receptors in the glands, leading to increasedsalivation.
Parotidglands
The two parotid glands are major salivary glands wrapped around
the mandibular ramus in humans
The largestof the salivary glands, they secrete saliva to facilitate
masticationand swallowing, andamylase to begin the digestionof
starches
It is the serous type of gland which secretesptyalinIt enters the oral
cavity via the parotid duct (Stensenduct).
The glands are locatedposteriorto the mandibular ramus and
anterior to the mastoid process ofthe temporal bone.
They are clinically relevant in dissections of facialnerve branches
while exposing the different lobes of it since any iatrogenic lesionwill
result in either loss of actionor strength of muscles involved in facial
expression
They produce 20% of the total salivary content in the oralcavity

2. Mumps is a viral infection, causedby infection in the parotid gland .
Submandibular gland
The submandibular glands (previously known as submaxillary
glands) are a pair of major salivary glands locatedbeneath the lower
jaws, superior to the digastric muscles. The secretionproduced is a
mixture of both serous fluid and mucus,
and enters the oral cavity via the submandibular duct or Wharton
duct.
65-70%of saliva in the oral cavity is produced by the
submandibular glands, even though they are much smaller than the
parotid glands.
This gland can usually be felt as it is in the superficialcervicalregion
and feels like a rounded ball. It is locatedabout two fingers above the
Adam's apple (laryngeal prominence) and about two inches apart
under the chin.
Sublingualglands
The sublingual glands are a pair of major salivary glands located
inferior to the tongue, anterior to the submandibular glands.
The secretionproduced is mainly mucous in nature; however, it is
categorizedas a mixed gland
Unlike the other two major glands, the ductal systemof the
sublingual glands does not have intercalatedducts and usually does
not have striatedducts either, so saliva exits directly from 8-20
excretoryducts knownas the Rivinus ducts.
Approximately 5% of saliva entering the oralcavity comes from
these glands.
Minorsalivaryglands

3. There are 800 to 1,000 minor salivary glands locatedthroughout the
oral cavity within the submucosaof the oral mucosa in the tissue of
the buccal, labial, and lingual mucosa, the soft palate, the lateral
parts of the hard palate, and the floor of the mouth or between
muscle fibers of the tongue.[
They are 1 to 2 mm in diameter and unlike the major glands, they
are not encapsulatedby connective tissue, only surrounded by it. The
gland has usually a number of acini connectedin a tiny lobule.
A minor salivary gland may have a common excretoryduct with
another gland, or may have its own excretory duct.
Their secretionis mainly mucous in nature and have many functions
such as coating the oralcavity with saliva. Problems with dentures
are sometimes associatedwith minor salivary glands if there is dry
mouth present(The minor salivary glands are innervated by the
seventh cranial or facialnerve.
Von Ebner's glands
Von Ebner's glands are glands found in a trough circling the
circumvallate papillae on the dorsal surface of the tongue near the
terminal sulcus. They secrete a purely serous fluid that begins lipid
hydrolysis. They also facilitate the perception of taste through
secretionofdigestive enzymes and proteins.
The arrangement of these glands around the circumvallate papillae
provides a continuous flow of fluid over the greatnumber of taste
buds lining the sides of the papillae, and is important for dissolving
the food particles to be tasted.
Nervesupply
Salivary glands are innervated, either directly or indirectly, by the
parasympathetic and sympathetic arms of the autonomic nervous
system. Parasympathetic stimulation evokes a copious flow of saliva.
In contrast, sympathetic stimulation produces either a small flow,
which is rich in protein, or no flow at all.
 Parasympathetic innervation to the salivary glands is carried
via cranialnerves.

4.  The parotid gland receives its parasympathetic input from the
glossopharyngealnerve (CN IX) via the otic ganglion,
 while the submandibular and sublingual glands receive their
parasympathetic input from the facial nerve (CN VII) via the
submandibular ganglion.
 These nerves release acetylcholine andsubstance P, which
activate the IP3 and DAG pathways respectively.
 Directsympatheticinnervation of the salivary glands takes
place via preganglionic nerves in the thoracic segments T1-T3
which synapse in the superior cervicalganglion with
postganglionic neurons that release norepinephrine, which is
then receivedby β-adrenergic receptors on the acinar and
ductal cells of the salivary glands, leading to an increase in
cyclic adenosine monophosphate (cAMP) levels and the
corresponding increase ofsaliva secretion.
 The sympathetic nervous system also affects salivarygland
secretions indirectly by innervating the blood vessels that
supply the glands.

Microanatomy
The gland is internally divided into lobules. Bloodvessels andnerves
enter the glands at the hilum and gradually branch out into the
lobules.
Acini
Secretorycells are found in a group, or acinus
Eachacinus is locatedat the terminal part of the gland connectedto
the ductal system, with many acini within eachlobule of the gland.
Eachacinus consists ofa single layer of cuboidal epithelial cells
surrounding a lumen, a central opening where the saliva is deposited
after being produced by the secretorycells.
The three forms of acini are classifiedin terms of the type of
epithelial cell present and the secretoryproduct being produced:
serous, mucoserous andmucous..

5. Ducts
In the duct system, the lumina are formed by intercalatedducts,
which in turn join to form striated ducts. These drain into ducts
situated betweenthe lobes of the gland (called interlobar ducts or
secretoryducts). These are found on most major and minor glands
(exception may be the sublingual gland)
All of the human salivary glands terminate in the mouth, where the
saliva proceeds to aid in digestion. The saliva that salivary glands
release is quickly inactivatedin the stomachby the acid that is
present there but the saliva also contains enzymes that are actually
activatedby the acid.
importance
Salivary glands secrete saliva which has many benefits for the oral cavity and
health in general. These benefits include:
 Protection
Saliva constitutes of proteins (for example; mucins) that lubricate and protect
the soft and hard tissues within the oral cavity. Mucins are the principal organic
constituents of mucus, the slimy visco-elastic material that coats all mucosal
surfaces.
 Buffering
In general, the higher the saliva flow rate, the faster the clearance and the higher
the buffer capacity hence better protection from dental caries. Therefore, people
with a slower rate of saliva combined with a low buffer capacity have a poor
salivary protection against microbes.[
 Pellicle formation
Saliva forms a pellicle on the surface of the tooth to prevent wearing. The film
contains mucins and proline-rich glycoprotein from the saliva. The proteins
(statherin and proline-rich proteins) within the salivary pellicle inhibit
demineralisation and promote remineralisation by attracting calcium ions.
 Maintenance of tooth integrity
Demineralization occurs when enamel disintegrates based on the presence of
acid. When this occurs, the buffering capacity effect of saliva (increases saliva

6. flow rate) inhibits demineralisation. Saliva can then begin to remineralise the
tooth by strengthening the enamel with calcium and phosphate minerals.
 Antimicrobial action
The saliva can prevent microbial growth based on the elements it contains. For
example; lactoferrin in saliva binds naturally with iron. Since iron is a major
component to bacterial cell walls, removal of iron breaks down the cell wall,
which in turn breaks down the bacteria. Antimicrobial peptides such as histatins
inhibit the growth of Candida albicans and Streptococcus mutans. Salivary
Immunoglobulins A serves to aggregate oral bacteria such as S. mutans and
prevent the formation of dental plaque.[]
 Tissue repair
Saliva can encourage soft tissue repair by decreasing clotting time and increasing
wound contraction.
 Digestion
Saliva contains the enzyme amylase that hydrolyses starch into maltose and
dextrin. Hence saliva allows digestion to occur before the food reaches the
stomach.
 Taste[
Saliva acts as a solvent in which solid particles can dissolve in and enter the taste
buds through oral mucosa located on the tongue. These taste buds are found
within foliate and circumvallate papillae, where minor salivary glands secrete
saliva.
Clinical significance
Micrograph of chronic inflammation of the salivary gland sialadenitis).
Main article: Salivary gland disease

7. A sialolithiasis (a salivary calculus or stone)may cause blockageof
the ducts, most commonly the submandibular ducts, causing pain
and swelling of the gland.
Salivary gland dysfunction refers to either xerostomia (the symptom
of dry mouth) or salivary gland hypofunction (reduced production of
saliva), it is associatedwith significant impairment of quality of life.
Following radiotherapy in the head and neck region, salivary gland
dysfunction is a predictable side-effect. Saliva production may be
pharmacologicallystimulated by sialagoguessuchas pilocarpine and
cevimeline. It can also be suppressedby so-calledantisialagogues
such as tricyclic antidepressants, SSRIs, antihypertensives, and
polypharmacy.
A Cochrane review found there was no strong evidence that topical
therapies are effective in relieving the symptom of dry mouth.
Cancertreatments including chemotherapy and radiation therapy
may impair salivaryflow.
Radiotherapycan cause permanent hyposalivation due to injury to
the oralmucosa containing the salivaryglands, resulting in
xerostomia, whereas chemotherapymay cause only temporary
salivary impairment.
Graft versus host disease afterallogeneicbone marrow
transplantation may manifest as dry mouth and many small
mucoceles. Salivarygland tumours may occur, including
mucoepidermoid carcinoma, a malignant growth.
Clinicaltests/investigations
A sialogramis a radiocontrast study of a salivary duct that may be
used to investigate its function and for diagnosing Sjögrensyndrome.
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