Parotid Gland

INTRODUCTION:
  • Parotid region contains the largest serous salivary gland 
  • Parotid gland is the largest major salivary gland.
  • Paired parotid glands lying largely below the external acoustic meatus between mandible and sternocleidomastoid muscle and it also projects forwards on the surface of masseter. Occupies the deep hollow behind the ramus of the mandible.
  • Wedge-shaped when viewed externally , with the base above & the apex behind the angle of the mandible.
  • On the surface of the masseter, small detached part lies between zygomatic arch and parotid duct called as Accessory parotid gland or ‘socia parotidis’ 
 PAROTID CAPSULE:
  • The investing layer of the deep cervical fascia splits(between the angle of the mandible and the mastoid process) to enclose the gland.
  • Consists of :-

  1. Superficial layer
  2. Deep layer 
  • Stylomandibular ligament separates the parotid glands from submandibular salivary gland.
  • The attachments of the Parotid fascia include :
  1. Anterior – Mandible
  2. Inferior – Stylomandibular ligament
  3. Posterior –Styloid process
SURFACES & BORDERS :
  • The gland has four surfaces:-
  1. Superior (base of the pyramid)
  2. Superficial
  3. Anteriomedial and
  4. Posteriomedial
  • The surfaces are seperated by 3 borders:
  1. Anterior:Seperates superficial surface from anteromedial surface
  2. Structures which emerge at this border:
  3. Parotid Duct
  4. Terminal Branches of facial nerve
  5. Transverse facial vessels
  6. Posterior:Seperates superficial surface from posteriomedial surface & Overlaps sternocleidomastoid.
  7. Medial:Seperates anteriomedial surface from posteriomedial surface Related to lateral wall of pharynx
DEVELOPMENT:
  • The parotid salivary glands appear early in the fourth week of prenatal development and are the first major salivary glands formed as an ectodermal furrow.
  • The epithelial buds of these glands are located on the inner part of the cheek, near the labial commissures of the primitive mouth.
  • These buds grow posteriorly toward the otic placodes of the ears and branch to form solid cords with rounded terminal ends near the developing facial nerve.
  • At 10 weeks of prenatal development, these cords are canalized and form ducts, with the largest becoming the parotid duct for the parotid gland.
  • The rounded terminal ends of the cords form the acini of the glands.
  • Secretion by the parotid glands via the parotid duct begins at about 18 weeks of gestation.
STRUCTURES WITHIN GLAND:
  • Arteries:
  1. External carotid artery(The arterial supply to the parotid gland is from the external carotid artery and its branches within and near the gland) Maxillary artery
  2. Superficial temporal vesseL
  3. Posterior auricular artery
  • Veins:
  1. The retromandibular veins is formed within the gland by the union of the superficial temporal and maxillary veins.
  2. In the lower part of the gland, the vein divides into anterior and posterior divisions which emerge at the apex of the gland.
  • Facial Nerve:
  1. It enters the gland through the upper part of its posteriomedial surface, and divides into its terminal branches within the glands.
  2. Branches appear on the surface at the anterior border.
  3. The arrangement of Branches of Facial nerve after exiting from Parotid gland is given the name as Pes Anserinus
PROCESSES :
  • The gland is an irregular lobulated mass, sends ‘processes’ in various directions.
  • These include:
  1. Glenoid process
  2. Facial process
  3. Accessory process
  4. Pterygoid process
  5. Carotid process
  6. Parotid Duct:
  7. Stenson’s duct
  • Course :-Forms by the union of smaller duct from the gland and run forwards and slightly downward on the masseter.
  • Relations
Superiorly:
  1. Accessory parotid gland.
  2. Upper buccal branch of the facial nerve.
  3. Transverse facial vessels.
  • Inferiorly:Lower buccal branch of the facial nerve.
  • Anterior border of the masseter, it turns medially and pierces:
  1. Buccal pad of fat.
  2. Buccalpharyngeal fascia
  3. Buccinator
  • The duct runs forward for a short distance between the buccinator and the oral mucosa.
  • The duct turns opens into the vestibule of the mouth (gingivo- buccal vestibule) opposite the crown of the upper 2nd molar tooth
NERVE SUPPLY:
  • Parotid gland is pierced but not innervated by facial nerve.
PARASYMPATHETIC(SECRETOMOTOR)
  • SUPPLY-derived from auriculo temporal nerve
  • The parasympathetic secretomotor fibres to parotid arises from the glossopharyngeal nerve.
  • The nerve reaches the gland via tympanic branch, the lesser petrosal nerve, the otic ganglion and the auriculotemporal nerve.
  • Postganglionic fibres to parotid gland is supplied by auriculotemporal nerve
SYMPTHETIC SUPPLY- vasomotor,
  • Derived from the plexus around the external carotid artery.
SENSORY NERVES-
  • From the auriculotemporal nerve, but the parotid fascia is innervated by the sensory fiberes of the great auricular nerve.
PAROTID LYMPH NODE:
  • The parotid lymph nodes lie partly in the superficial fascia and partly deep to the deep fascia over the parotid gland.
  • They drain:-
  1. Temple
  2. Side of the scalp
  3. Lateral surface of the auricle
  4. External acoustic meatusv> Middle earv Parotid glandv Upper part of cheek
  5. Parts of the eyelids
  6. Orbit
  • Efferents from these nodes pass to the upper groups of the deep cervical nodes.
Exam Question
  • Secretomotor fiber to parotid salivary gland is supplied by otic ganglion
  • The arrangement of Branches of Facial nerve after exiting from Parotid gland is given the name as Pes Anserinus 
  • Parotid duct pierces buccinator muscle
  • Parotid gland is pierced but not innervated by facial nerve.
  • The parasympathetic secretomotor fibres to parotid arises from the glossopharyngeal nerve & reaches the gland via tympanic branch, the lesser petrosal nerve, the otic ganglion and the auriculotemporal nerve.
  • Parotid capsule is derived from deep cervical fascia
  • External carotid artery(The arterial supply to the parotid gland is from the external carotid artery and its branches within and near the gland)
  • Postganglionic fibres to parotid gland is supplied by auriculotemporal nerve
  • Parotid duct is also k/as Stenson’s duct
  • The duct turns opens into the vestibule of the mouth (gingivo- buccal vestibule) opposite the crown of the upper 2nd molar tooth
  • Parotid duct pierces Buccal pad of fat,Buccalpharyngeal fascia & Buccinator
  • STRUCTURES WITHIN GLAND are External carotid artery,Maxillary artery, Superficial temporal vessel, Posterior auricular artery,retromandibular veins,Facial Nerve

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