chapter 5

• Parotid region


  Contains the largest serous salivary gland and the 'queen of the face', the facial nerve

  
• Parotid gland


  • Contains vertically disposed blood vessels and horizontally situated facial nerve and its various branches
  • Gets affected by virus of mumps, which can extend the territory of its attack up to gonads as well
  • Incising the parotid abscess requires care of the branches of facial nerve by giving horizontal incision
• Large salivary glands


  • Parotid
  • Submandibular
  • Sublingual
• There are numerous small glands in the tongue, the palate, the cheeks and the lips. These glands produce saliva which keeps the oral cavity moist, and helps in chewing and swallowing. The saliva also contains enzymes that aid digestion.
• Parotid gland

  (Para = around; otic = ear)
• Parotid gland


  • It is the largest of the salivary glands
  • It weighs about 25 g
  • It is situated below the external acoustic meatus, between the ramus of the mandible and the sternocleidomastoid
  • Anteriorly, the gland also overlaps the masseter muscle
  • Skin over the gland is supplied by great auricular nerve (C2, C3)

  
• Capsule of parotid gland


  • The investing layer of the deep cervical fascia forms a capsule for the gland
  • It is supplied by great auricular nerve
  • The fascia splits (between the angle of the mandible and the mastoid process) to enclose the gland
  • The superficial lamina/parotidomasseteric fascia, thick and adherent to the gland, is attached above to the zygomatic arch
  • The deep lamina is thin and is attached to the styloid process, tympanic plate, the angle and posterior border of the ramus of the mandible
  • A portion of the deep lamina, extending between the styloid process and the mandible, is thickened to form the stylomandibular ligament which separates the parotid gland from the submandibular salivary gland
  • The ligament is pierced by the external carotid artery
• Parotid gland


  • It resembles a three-sided pyramid
  • The apex of the pyramid is directed downwards
• Surfaces of parotid gland


  • Superior (base of the pyramid)
  • Superficial
  • Anteromedial
  • Posteromedial
• Borders of parotid gland


  • Anterior
  • Posterior
  • Medial/pharyngeal edge

  
• Apex of parotid gland


  • It overlaps the posterior belly of the digastric and the adjoining part of the carotid triangle
  • The cervical branch of the facial nerve and the two divisions of the retromandibular vein emerge near the apex

  
• Superior surface of parotid gland


  • forms the upper end of the gland which is small and concave
  • It is related to the cartilaginous part of the external acoustic meatus
  • The posterior surface of the temporomandibular joint
  • The superficial temporal vessels
  • The auriculotemporal nerve
• Superficial surface of parotid gland


  • It is covered with skin
  • Superficial fascia containing the anterior branches of the great auricular nerve, the preauricular or superficial parotid lymph nodes and the posterior fibres of the platysma and risorius
  • The parotid fascia which is thick and adherent to the gland
  • A few deep parotid lymph nodes embedded in the gland
• Anteromedial surface of parotid gland


  • It is grooved by the posterior border of the ramus of the mandible
  • It is related to the masseter
  • The lateral surface of the temporomandibular joint
  • The posterior border of the ramus of the mandible
  • The medial pterygoid
  • The emerging branches of the facial nerve

  
• Posteromedial surface of parotid gland


  • It is moulded to the mastoid and the styloid processes and the structures attached to them
  • It is related to the mastoid process, with the sternocleidomastoid and the posterior belly of the digastric
  • The styloid process, with structures attached to it
  • The external carotid artery and facial nerve enter the gland through this surface
  • The internal carotid artery lies deep to the styloid process

  
• Anterior border of parotid gland


  • It separates the superficial surface from the anteromedial surface
  • It extends from the anterior part of the superior surface to the apex
  • The parotid duct
  • Most of the terminal branches of the facial nerve
  • The transverse facial vessels emerge at this border
  • The accessory parotid gland lies on the parotid duct close to this border

  
• Posterior border of parotid gland


  • It separates the superficial surface from the posteromedial surface
  • It overlaps the sternocleidomastoid
• Medial edge or pharyngeal border of parotid gland


  • It separates the anteromedial surface from the posteromedial surface
  • It is related to the lateral wall of the pharynx

  
• Structures within the parotid gland from medial to lateral side

  • Arteries: External carotid artery, maxillary artery, superficial temporal artery
  • Veins: Retromandibular vein
  • Facial nerve

  
• Facial nerve in the parotid gland

  • It leaves the skull by passing through the stylomastoid foramen
  • It crosses the lateral side of the base of the styloid process
  • It enters the posteromedial surface of the parotid gland, runs forwards through the gland crossing the retromandibular vein and the external carotid artery
  • Behind the neck of the mandible, it divides into two branches—temporofacial and cervicofacial
  • Temporofacial gives temporal and zygomatic branches
  • Cervicofacial gives buccal, marginal mandibular and cervical branches
  • These five terminal branches emerge along the anterior border and apex of the parotid gland

  
• Branches of facial nerve at its exit from the stylomastoid foramen

  • Communicating branches with adjacent cranial and spinal nerves
  • The posterior auricular nerve
  • The digastric branch
  • The stylohyoid branch

  
• Terminal branches of facial nerve

  • Temporal branches
  • Zygomatic branches
  • Buccal branches
  • Marginal mandibular branch
  • Cervical branch

  
• Bell's palsy


  Sudden paralysis of facial nerve at the stylomastoid foramen, results in asymmetry of corner of mouth, inability to close the eye, disappearance of nasolabial fold and loss of wrinkling of skin of forehead on the same side
• Patey's faciovenous plane


  • The gland is composed of a large superficial and a small deep part, the two being connected by an 'isthmus' around which facial nerve divides

  
• Accessory processes of parotid gland

  • Facial process—along parotid duct. It lies between zygomatic arch and the parotid duct
  • Pterygoid process—between mandibular ramus and medial pterygoid
  • Glenoid process—between external acoustic meatus and temporomandibular joint
  • Poststyloid process

  
• Blood supply of parotid gland

  • It is supplied by the external carotid artery and its branches that arise within the gland
  • The veins drain into the external jugular vein and internal jugular vein
• Nerve supply of parotid gland

  • Parasympathetic nerves are secretomotor
  • They reach the gland through the auriculotemporal nerve
  • The preganglionic fibres begin in the inferior salivatory nucleus; pass through the glossopharyngeal nerve, its tympanic branch, the tympanic plexus and the lesser petrosal nerve; and relay in the otic ganglion
  • The postganglionic fibres pass through the auriculotemporal nerve

  
• Parotid gland


  Superficial and a small deep part, the two being connected by an 'isthmus' around which facial nerve divides

  
• Accessory processes of parotid gland

  • Facial process - along parotid duct, between zygomatic arch and parotid duct
  • Pterygoid process - between mandibular ramus and medial pterygoid
  • Glenoid process - between external acoustic meatus and temporomandibular joint
  • Poststyloid process

  
• Blood supply of parotid gland

  Supplied by external carotid artery and its branches, veins drain into external jugular vein and internal jugular vein
• Parasympathetic nerve supply to parotid gland


  Preganglionic fibres begin in inferior salivatory nucleus, pass through glossopharyngeal nerve, tympanic branch, tympanic plexus and lesser petrosal nerve, relay in otic ganglion, postganglionic fibres pass through auriculotemporal nerve

  
• Sympathetic nerve supply to parotid gland


  Postganglionic, vasomotor, derived from plexus around middle meningeal artery, start from lateral horn of T1 segment of spinal cord, synapse in superior cervical ganglion, postganglionic fibres travel along branches of external carotid and maxillary arteries

  
• Sensory nerve supply to parotid gland

  From auriculotemporal nerve, parotid fascia innervated by great auricular nerve (C2, C3)

  
• Lymphatic drainage of parotid gland

  • Parotid nodes - drain temple, side of scalp, lateral surface of auricle, external acoustic meatus, middle ear, parotid gland, upper part of cheek, parts of eyelids and orbit, efferents pass to upper deep cervical nodes
• Parotid duct/Stenson's duct


  Thick-walled, about 5cm long, emerges from middle of anterior border of gland, runs forwards and slightly downwards on masseter, relations

  
  

  superiorly - accessory parotid gland, transverse facial vessels, upper buccal branch of facial nerve,

  
  

  inferiorly - lower buccal branch of facial nerve, turns medially and pierces buccal pad of fat, buccopharyngeal fascia, buccinator, opens into vestibule of mouth opposite upper 2nd molar tooth
• Facial nerve courses through parotid gland without supplying any structure in it
• Skin over parotid gland is supplied by great auricular nerve (C2, C3)
• Deepest structure in parotid gland is external carotid artery
• Otic ganglion is the only parasympathetic ganglion with four roots, including a motor root
• Facial nerve divides into temporofacial and cervicofacial branches, temporofacial gives temporal and zygomatic branches, cervicofacial gives buccal, marginal mandibular and cervical branches