ANATOMY OF THE SALIVARY GLANDS IN THE HEAD AND NECK

Jo’rabek  Nurulloyev

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ANATOMY OF THE SALIVARY GLANDS IN THE HEAD AND NECK

Nurulloyev Jo’rabek Shavkiddinovich

Assistant reacher of the Alfraganus university

ORCID ID: 0009-0003-4777-1881

Email: JurabekDoctor@mail.ru

https://doi.org/10.5281/zenodo.14603072

Introduction

Salivary glands are exocrine glands that produce, modify, and secrete saliva into the oral

cavity. These glands are classified into two main types: major salivary glands, which include
the parotid, submandibular, and sublingual glands, and minor salivary glands, which are
distributed throughout the mucosa of the upper aerodigestive tract and most of the oral
cavity.

Human salivary glands secrete between 0.5 and 1.5 liters of saliva daily. Saliva plays a

crucial role in facilitating chewing, swallowing, and speech, as well as lubricating the oral
mucosa and serving as a medium for taste perception. It aids in the digestion of starches and
triglycerides through enzymes like amylases and lipases. Additionally, saliva serves a
protective function against infections with its various organic components, such as
immunoglobulin A (IgA), lysozymes, autolysin, and lactoferrin. Saliva also contains
bicarbonates that neutralize bacterial acids and safeguard the oral cavity and esophagus from
gastric acids, thereby playing an essential role in preventing infections and dental caries.

Structure and Function
Anatomical Location



Parotid Gland (PG):

The largest of the major salivary glands, located between the

sternocleidomastoid and masseter muscles, extending from the mastoid tip to the angle of the
mandible. Its superficial layer contains the facial nerve, retromandibular vein, and external
carotid artery, making it a critical site for surgical considerations. Stensen’s duct extends from
the anterior part of the gland, crosses the masseter muscle, and opens into the oral cavity near
the second maxillary molar.



Submandibular Gland (SMG):

The second-largest salivary gland, situated below the

mandible between the anterior and posterior bellies of the digastric muscle. It consists of
smaller anterior and larger posterior lobes, connected by the mylohyoid muscle. Wharton’s
duct, its primary excretory duct, opens at the sublingual caruncle, with the hypoglossal nerve
running parallel to it.



Sublingual Gland (SLG):

Positioned beneath the floor of the mouth, this gland lies

between the mandible and genioglossus muscle and superior to the mylohyoid muscle. Unlike
other major glands, it lacks a single primary duct and instead has numerous small ducts
(Rivinus ducts) that directly open into the mouth. Bartholin's duct may also connect to the
submandibular duct at the sublingual caruncle.

Architecture and Function

Salivary glands consist of acinar cells, ductal cells, and myoepithelial cells. Despite their

varied locations, they share a common structure of branched ducts leading to secretory acini
that produce saliva.
1.

Acinar Cells:

These cells are classified into serous, mucinous, and seromucous types.

The parotid gland contains predominantly serous acini, producing watery saliva. The

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submandibular and sublingual glands are mixed, with the submandibular gland containing
more serous acini and the sublingual gland having more mucinous acini.
2.

Ductal System:

Saliva is modified as it passes through the ductal system, which consists

of intercalated, striated, and excretory ducts. Intercalated ducts secrete bicarbonate and
absorb chloride, while striated ducts regulate sodium and potassium levels. The excretory
ducts have the largest diameter and deliver saliva to the oral cavity.

Myoepithelial cells encase the acini and ducts, contracting to facilitate saliva flow. The

glands are supported by an extracellular matrix, immune cells, stromal elements, and nerve
fibers, ensuring efficient function.

The unique combination of structural features and cellular composition enables salivary

glands to perform critical roles in digestion, oral lubrication, taste, and protection against
microbial infections.

Embryology

The development of salivary glands begins around the 6th to 8th week of gestation when

interactions between the oral ectoderm and the adjacent mesenchyme trigger the thickening
of the epithelial layer. This process leads to branching morphogenesis, characterized by
systematic stages of proliferation, clefting, differentiation, migration, programmed cell death,
and complex interactions among mesenchymal, epithelial, endothelial, and neuronal cells.
Similar branching processes are observed in other organ systems, such as the lungs, kidneys,
and mammary glands. By the 14th week of gestation, the terminal buds at the ends of the
branched ductal structures develop into acini.

The parotid gland is the first to form but the last to be enclosed in connective tissue due

to the development of lymphatic tissue within the gland. This unique feature makes it the only
salivary gland with an enclosed lymphatic system. Submandibular glands become well-
differentiated between the 13th and 16th weeks, displaying microvilli, desmosomes, and a
basal lamina surrounding the epithelium. Myoepithelial cells also begin to emerge during this
period. By the 16th week, striated and intercalated ducts are evident, and gland development
concludes by the 28th week, when acini begin producing secretory products. At birth, the
glands are fully functional.

Blood Supply and Lymphatics

Parotid Gland

The parotid gland receives its blood supply from the external carotid artery, which

ascends from the carotid bifurcation along the posterior aspect of the digastric muscle. This
artery bifurcates into the superficial temporal artery, which runs to the scalp, and the
maxillary artery, which supplies blood to the infratemporal and pterygopalatine fossae.
Additionally, the transverse facial artery branches off the superficial temporal artery,
supplying the parotid gland, duct, and masseter muscle.

Venous drainage occurs through the retromandibular vein, formed by the union of the

maxillary and superficial temporal veins. This vein traverses the parotid gland anterior to the
facial nerve and joins the external jugular vein. Anatomical variations may result in the
retromandibular vein splitting into anterior and posterior branches. The anterior branch may
unite with the posterior facial vein to form the common facial vein, while the posterior branch
drains into the external jugular vein via the post-auricular vein.

Submandibular Gland

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The submandibular gland primarily receives its blood supply from the facial artery, a

branch of the external carotid artery. The facial artery runs medially to the posterior belly of
the digastric muscle, projecting through the gland capsule before crossing the mandible at the
facial notch and ascending into the face.

Lymph nodes associated with the submandibular gland are located between the gland

and its fascia, rather than within the gland itself. These nodes are closely linked to the facial
artery and vein and drain into the deep cervical and jugular lymphatic chains.

Sublingual Gland

The sublingual gland is supplied by the submental and sublingual arteries, which branch

from the lingual and facial arteries. Venous drainage parallels the arteries and empties into
the submandibular lymph nodes, which manage the lymphatic drainage of the gland.

Nerves

Salivary glands receive both parasympathetic and sympathetic innervation, each playing

distinct roles. Parasympathetic innervation promotes serous saliva production and ion
secretion, while sympathetic innervation enhances protein secretion and regulates glandular
blood flow, as well as local inflammatory and immune responses.



Parotid Gland:

Innervation is provided by the glossopharyngeal nerve (cranial nerve

IX). Parasympathetic fibers originate in the otic ganglion and join the auriculotemporal nerve
to reach the gland.



Submandibular and Sublingual Glands:

Parasympathetic fibers originate from the

superior salivatory nucleus in the pons and travel via the facial nerve (cranial nerve VII). They
pass through the chorda tympani, exit the skull through the petrotympanic fissure, and join
the lingual nerve before synapsing in the submandibular ganglion. Sympathetic innervation
stems from the superior cervical ganglion, with postganglionic fibers reaching the glands
along blood vessels branching from the carotid plexus.

Minor salivary glands are not regulated by neuronal input but secrete saliva

continuously, ensuring consistent lubrication of oral surfaces, even when major glands are
inactive.

Surgical Considerations

Identifying the facial nerve is critical during parotid and submandibular gland surgeries

to prevent complications. In parotidectomies, careful tumor removal with tissue margin
preservation is prioritized while safeguarding facial nerve function. Reliable anatomical
landmarks for locating the nerve include bony structures like the tympanomastoid fissure,
while soft tissue landmarks are less consistent. In submandibular and sublingual gland
surgeries, understanding the anatomy of the floor of the mouth is essential. The lingual
nerve’s proximity to Wharton’s duct makes it particularly susceptible to injury during
procedures for conditions like sialolithiasis.

Clinical Significance

Salivary gland dysfunction is often associated with systemic conditions, such as diabetes,

hormonal imbalances, arteriosclerosis, and neurologic disorders. Common issues include:
1.

Xerostomia:

Caused by medications, systemic conditions, or damage to the glands, it

can lead to increased susceptibility to infections and dental caries. Treatments include
sialogogues like pilocarpine and cevimeline, which stimulate saliva production, or saliva
substitutes.