Salivary glands -1

Presented by

Dr. Shrikant Sonune

Guided by

Dr Ashok Patil,

Dr Shilpa Kandalgaonkar,

Dr Mayur Choudhari,

Dr Suyog Tupsakhare,

Dr Mahesh Gabhane.

Content Introduction

Development of Salivary Glands

Anatomy

Parotid gland

Submandibular gland

Sublingual gland

Minor salivary gland

Histology of salivary gland

References

Introduction Salivary glands are compound, tubuloacinar exocrine

glands whose ducts open into the oral cavity.

The major salivary glands are the paired Parotid

Submandibular

Sublingual glands

In addition, there are numerous minor salivary glands scattered throughout the oral mucosa and submucosa.

Introduction They secrete saliva, a fluid which

Lubricates food to assist deglutition,

Moistens the buccal mucosa, which is important for speech, and

Provides an aqueous solvent necessary for taste.

Contains digestive enzymes, e.g. salivary amylase

Antimicrobial agents e.g. IgA, lysozyme etc

Development of Salivary Gland


During the fetal life each salivary gland is formed at specific location in the oral cavity

The parotid develops in the lateral aspects of the stomodeum,

The submandibular and sublingual develop in the floor of the stomodeum.

Primordia for

Parotid & submandibular -- during 4th to 6th week, Sublingual -- after 7 to 8 week Minor salivary glands -- 3rd month.

The cells of secretory end pieces attain maturity during the last 2 month of gestation.


Individual salivary glands arise as a proliferation of oral epithelial cells, forming a focal thickening that grows into underlying ectomesenchyme.

Continued growth results in formation of a small bud connected to the surface by a trailing cord condensing around the bud.


Initially it is solid but gradually develops lumen & become duct.

Secretory portion develop later than the duct system.

The mesenchyme into which the glandular epithelium grow produces factor or factors that stimulate the growth of gland.


The process of branching morphogenesis,

That is formation of hollow tubular organ from an initially flat epithelial surface,

To be related the presence of microfilaments in the epithelial cells.

5 to 7 nm thickForm a network


Contractile protein actin present in apical & basal ends of cells. Deferential contraction pulls cells outwards forming cleft in solid cord. This cleft is maintained by deposition of extracellular matrix in the cleft.

Thus, Clefts develop in the bud, forming two or more new buds; continuation of this process, called branching morphogenesis,

Produces successive generations of buds and a hierarchical ramification of the gland.


The development of a lumen within branched epithelium generally occurs first in the distal end of main cord and in branched cord, then in the proximal end of main cord.

The lumina form within ducts before they develop within the terminal buds.


Lumen formation may involve apoptosis of centrally located cells in the cell cord.

Following development of lumen in terminal buds, the epithelium consists of two layers of cells.

Inner layer Cells of inner layer differentiate into secretory cells of mature glands.

Outer layer (Some cells) form the contractile myoepithelial cells that are present around the secretory end pieces & intercalated duct.


Connective tissue

Salivary gland has connective tissue component that diminishes as parenchyma expands;

Even so every terminal end piece and every duct remain supported by tenuous connective tissue

component carrying blood vessels and nerves.

(The presence of functional innervations is also essential to proper growth & maintenance of salivary glands structure.)


Post natal growth

The glands continue to grow postnatally with the volume proportion of acinar tissue increasing up to 2 yr of age.

The volume proportion of ducts, connective tissue and vascular elements decreasing up to 2 yr of age.


Anatomy of Salivary glands

Parotid gland

The paired parotid glands are the largest of the salivary glands.

The gland is an irregular, lobulated, yellowish mass, lying largely below the external acoustic meatus between the mandible and sternocleidomastoid muscle.

The gland also projects forwards on the surface of masseter.

In 20% of cases, a small, usually detached, part called the accessory parotid gland lies between the zygomaticarch above and the parotid duct below.

Parotid gland

Structures within Parotid gland From medial to the lateral

side these are:

Arteries:

External carotid artery

Maxillary artery

Superficial temporal vessel

Posterior auricular artery

Veins:

Retromandibular vein

Facial nerve

Structures within Parotid gland

Arteries

External carotid artery: enters the gland through its posteromedial surface

It divides into The maxillary artery,

which emerges from the anteromedial surface, and

The superficial temporal artery which gives off its transverse facial branch in the gland.


Maxillary artery leaves the gland through its anteromedial surface.

Superficial temporal vessel: emerge at the anterior part of the superior surface

Posterior auricular artery may arise within the gland.

Veins :

The Retromandibular vein is formed within the gland by the union of superficial temporal and maxillary veins.


Nerves:

Facial nerve enters the gland through the upper part of its posteromedial surface.

The nerve divides into its terminal branches within the gland.


Parotid duct

The parotid duct begins by the confluence of two main tributaries within the anterior part of the gland.

It appears at the anterior border of the upper part of the gland and passes horizontally across masseter, approximately at the level midway between the angle of the mouth and the zygomatic arch.

Parotid duct

While crossing masseter it can receive the accessory parotid duct and lies between the upper and lower buccal branches of the facial nerve.

The duct is 5 cm long and its lumen is 3 mm wide.

Vascular supply The arterial supply to the parotid gland is from the

external carotid artery and its branches within and near the gland.

The veins drain to the external jugular vein via local tributaries.

Lymphatic drainage Lymph nodes are found both in the skin overlying the

parotid gland (preauricular nodes) and in the substance of the parotid gland itself.

There are usually 10 lymph nodes present in the gland.

The majority are found in the superficial part of the gland lying above the plane related to the facial nerve.

Lymphatic drainage

The deeper part of the parotid gland beneath the branches of the facial nerve contains one or two lymph nodes.

Lymph from the parotid gland drains to the upper deep cervical lymph nodes.

Nerve supplyParasympathetic nerves(secretomotor)

Inferior salivatory nucleus

Glossophyrengal nerve.(tympanic branch)

Tympanic plexus

Lesser petrosal nerve

Otic ganglion

Auriculotemporal nerve

Parotid gland

Nerve supply

Sympathetic nerve supply:

Vasomotor -Derived from the plexus around the external carotid artery

Sensory nerve supply:

Auriculotemporal nerve

Clinical consideration Because of fibrous fascia is covering the parotid, its

inflammatory swelling is tense and hard.

Parotid duct is slightly larger along their course than at their caruncle.

This permits storage of secretions so that a ready flow may be available on stimulation without waiting for secretory process.

Clinical consideration

This relatively static reservoir may form obstructions and are a ready nidus for bacterial activity.

The close association of the facial nerve with the gland is very important consideration, during surgical procedures.

Submandibular salivary gland

The submandibular gland is irregular in shape and about the size of a walnut.

It consists of a larger superficial and a smaller deep part, continuous with each other around the posterior border of mylohyoid.

It is a seromucous (but predominantly serous) gland.

SUPERFICIAL PART OF THE SUBMANDIBULAR GLAND

The superficial part of the gland is situated in the digastric triangle where it reaches forward to the anterior belly of digastric and back to the stylomandibular ligament.

Above, it extends medial to the body of the mandible.


Below, it usually overlaps the intermediate tendon of digastrics and the insertion of stylohyoid.

The superficial layer is attached to the lower border of the mandible and covers the inferior surface of the gland.

The deep layer is attached to the mylohyoid line on the medial surface of the mandible and covers the medial surface of the gland.

The inferior surface, covered by skin, platysma and deep fascia, is crossed by the facial vein and the cervical branch of the facial nerve.

Near the mandible the submandibular lymph nodes are in contact with the gland and some may be embedded within it.



The lateral surface is related to

The submandibular fossa on the medial surface of the body of the mandible and

The mandibular attachment of medial pterygoid.


The facial artery:

Grooves its poster superior part,

Lies at first deep to the gland and

Emerges between its lateral surface and the mandibular attachment of the medial pterygoid to reach the lower border of the mandible.

The medial surface is related anteriorly to mylohyoid, from which it is separated by the mylohyoid nerve and vessels and branches of the submental vessels.

More posteriorly, it is related to styloglossus, the stylohyoid ligament and the glossopharyngeal nerve, which separate it from the pharynx.

Below, the medial surface is related to the stylohyoid muscle and the posterior belly of digastric.


DEEP PART OF THE SUBMANDIBULAR GLAND

The deep part of the gland extends forwards to the posterior end of the sublingual gland.

It lies Between mylohyoid inferolaterally, hyoglossus and

styloglossus medially, The lingual nerve superiorly, and The hypoglossal nerve and deep lingual vein inferiorly.

Vascular supply and lymphatic drainage

The arteries supplying the gland are branches of the facial and lingual arteries.

The lymph vessels drain into the deep cervical group of lymph nodes (particularly the jugulo-omohyoid node), interrupted by the submandibular nodes.

Submandibular duct

Submandibular duct Also known as Wharton's duct.

The submandibular duct is 5 cm long and has a thinner wall than the parotid duct.

It begins from numerous tributaries in the superficial part of the gland and emerges from the medial surface of this part of the gland behind the posterior border of mylohyoid.

It traverses the deep part of the gland, passes at first up and slightly back for 5 mm, and then forwards between mylohyoid and hyoglossus.

Submandibular duct It next passes between the sublingual gland and

genioglossus to open in the floor of the mouth on the summit of the sublingual papilla at the side of the frenulum of the tongue.

It lies between the lingual and hypoglossal nerves on hyoglossus, but, at the anterior border of the muscle, it is crossed laterally by the lingual nerve, terminal branches of which ascend on its medial side.

As the duct traverses the deep part of the gland it receives small tributaries draining this part of the gland.

Innervation The secretomotor supply

Superior salivatory nucleus

Facial nerve

Chorda tympani

Submandibular ganglion

Postganglionic parasympathetic fiber supplying gland.

Sensory nerve supply:

Lingual nerve

Vasomotor nerve supply:

Plexus around the facial artery

VASCULAR SUPPLY AND LYMPHATIC DRAINAGE

The arteries supplying the gland are branches of the facial and lingual arteries.

The veins drain into the common facial or lingual vein.

The lymph vessels drain into the deep cervical group of lymph nodes (particularly the jugulo-omohyoid node), interrupted by the submandibular nodes.

Clinical considerations The entire submandibular gland and duct system lies

in a dependent position, which predisposes it to retrograde invasion by oral flora.

Similar to the parotid duct, the Wharton’s duct is also wider before reaching the papilla. This can lead to stangulation of saliva and the organic matter.

The sharp bends of Wharton’s duct at the posterior border of the mylohyoid muscle allows stasis of the saliva favoring the formation of salivary stones.

Sublingual salivary gland

The sublingual gland is the smallest of the main salivary glands: each gland is narrow, flat, shaped like an almond, and weighs 4 g.

The sublingual gland lies on mylohyoid, and is covered by the mucosa of the floor of the mouth, which is raised as a sublingual fold.

The anterior end of the contralateral sublingual gland lies in front, and the deep part of the submandibular gland lies behind.


The mandible above the anterior part of the mylohyoid line, the sublingual fossa, is lateral, and genioglossus is medial, separated from the gland by the lingual nerve and submandibular duct.

The sublingual glands are seromucous, but predominantly mucous.

VASCULAR SUPPLY AND LYMPHATIC DRAINAGE

The arterial supply is from the sublingual branch of the lingual artery and the submental branch of the facial artery.

Lymphatic drainage is to the submental nodes.

InnervationParasympathetic(secertomotar)

Superior salivatory nucleus

Facial nerve

Chorda tympani

Submandibular ganglion

Postganglionic parasympathetic fiber supplying gland

Sympathetic: via plexus around facial artery

Sensory: Lingual nerve

SUBLINGUAL DUCTS The sublingual gland has 8-20 excretory ducts. Smaller

sublingual ducts open, usually separately, from the posterior part of the gland onto the summit of the sublingual fold (a few sometimes open into the submandibular duct).

Small rami from the anterior part of the gland sometimes form a major sublingual duct (Bartholin's duct), which opens with, or near to, the orifice of the submandibular duct.

This duct may be visualized occasionally in a submandibular sialogram.

Minor salivary glands Minor salivary glands are found throughout the oral cavity,

except in the anterior part of the hard palate & the gingiva.

The minor salivary glands of the mouth include: Labial ,

Buccal ,

Palatoglossal ,

Palatal

Lingual glands.

The labial and buccal glands contain both mucous and serous elements.

The palatoglossal glands are mucous glands and are located around the pharyngeal isthmus.

Minor salivary glands

The palatal glands are mucous glands and occur in both the soft and hard palates.

The anterior and posterior lingual glands are mainly mucous.

The anterior glands are embedded within muscle near the ventral surface of the tongue and open by means of four or five ducts near the lingual frenum and the posterior glands are located in the root of the tongue.

The deep posterior lingual glands are predominantly serous.

Serous glands (of Von Ebner) occur around the circumvallate papillae, their secretion is watery, help in spreading taste stimuli over the taste buds and then washing them away.

Minor salivary glands

Clinical consideration The sublingual gland and the minor salivary glands

have short ducts, where the chances of stasis are less.

Thus, obstructive lesions do not occur in the glands.

Since minor salivary glands are placed superficially, the traumatic lesions such as Mucoceles commonly affect these glands.

References Ten Cate’s Oral histology Development, Structure and

Function Sixth Edition

General Anatomy 3rd vol. by B. D. Chaurasia

Textbook of Human Histology Inderbir Singh

Textbook of Oral and maxillofacial Surgery by NeelimaMalik

Salivary glands -1

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