Editing Parotid

== '''Function''' ==

* Predominantly a serous     salivary gland
* Secretes saliva via the     parotid duct into the oral cavity to facilitate mastication and swallowing

== '''Embryology''' ==

* From ectoderm
* Forms as a groove in the     cheek, with ectodermal cells in the blind end of that groove/tunnel     forming the gland

== '''Gross anatomy''' ==

* Average weight 25g
* Three surfaces - lateral,     anterior and deep
* Roughly triangular when     viewed from laterally
* Made up of a larger     superficial lobe and a smaller deep lobe (deep to ramus of mandible)
* Irregular, lobulated,     yellowish mass
* The two lobes are separated     by the facial nerve
* Enclosed within an unyielding     parotid capsule, derived from investing layer of deep cervical fascia
** This fascia attaches to      styloid process and mandible in front of the gland - the stylomandibular      ligament, which separates parotid from submandibular gland
** The fascia also connects the      posterior parotid to the external auditory canal
* Can have an accessory parotid     gland between the zygomatic arch above and parotid duct below


== '''Parotid duct (of Stensen)''' ==

* Exits from front of gland
* 5cm long
* Lies on masseter
* Dives deeply around the     muscle's anterior border, through buccal fascia, to open inside the cheek,     opposite second molar upper tooth
* Can be an accessory parotid     duct on the masseter between the duct and the zygomatic arch

== '''Relations''' ==

* Below external acoustic     meatus, between mandible and SCM
* Also projects forward onto     surface of masseter
* Posteriorly lies over SCM -     greater auricular nerve and EJV seen here
* Traversed by (from deep to     superficial):
** Auriculotemporal nerve -      branch of mandibular division of trigeminal nerve, communicating with      facial nerve within parotid. Damage is thought to relate to Frey's      syndrome - sweating of pre-auricular skin when sweating.
** External carotid artery -      enters posteromedial surface and divides into maxillary artery and STA,      and sometimes transverse facial artery, which tends to run parallel with      but above the parotid duct
** Retromandibular vein -      superficial to ECA. Sometimes forms within the gland from superficial      temporal and maxillary veins.
** Facial nerve - stays      superior to blood vessels - see separate topic - very variable anatomy
* May be covered by platysma     antero-inferiorly

== '''Blood supply''' ==

* Branches from ECA
* Venous drainage to the     retromandibular vein

== '''Lymphatic drainage''' ==

* Nodes within the parotid     sheath

== '''Innervation''' ==

* Fibres from inferior salivary     nucleus in the medulla
** Travel on glossopharyngeal      nerve and its tympanic branch
** Give rise to tympanic plexus      on the promontory of the cochlear in the middle ear
** These fibres pass via the      lesser petrosal nerve to synapse in the otic ganglion
** Post-ganglionic secretomotor      fibres reach the parotid hitch-hiking along with the auriculotemporal      nerve
* Sympathetic (vasoconstrictor)     from the superior cervical ganglion
* Sensory
** From parotid gland itself      via auriculotemporal nerve
** From parotid fascia via      greater auricular nerve


== '''Variant anatomy''' ==

* Accessory duct
* Accessory gland







[[Category:Anatomy]]