14 - Parotid region and facial nerve Flashcards
What is the parotid gland and what is its function?
- largest of the salivary glands
- almost entirely serous secretions, no mucus
Where is the parotid gland located?
- parotid bed
- outside of the oral cavity
- anterior and inferior to the ear
- stretches from the zygoma to the inferior border of the mandible
Describe the fascia surrounding the parotid gland.
Investing fascia called the parotid sheath
Describe the location of the parotid duct.
- passes anteriorly and horizontally from the parotid duct
- pierces buccinator
- enters the oral cavity at the 2nd maxillary molar
What structures are embedded within the parotid gland?
- retromandibular vein
- ECA
- parotid lymph nodes
- CN VII
Describe the blood supply of the parotid gland.
- ECA runs through the gland
- branches of the ECA supply the gland (superficial temporal and maxillary arteries)
Describe the venous drainage of the parotid gland.
- maxillary
- superficial temporal
- these 2 veins form the retromandibular vein which drains to the IJV and EJV
Describe the parasympathetic innervation of the parotid gland.
- parasympathetic (secretomotor)
- preganglionic fibres from CN IX travel to the otic ganglion by the tympanic and lesser petrosal nerve
- postganglionic fibres from the otic ganglion pass to the auriculotemporal (CN V3) which sends branches to the parotid
Describe the sympathetic innervation of the parotid gland.
- vasoconstriction and reduction in saliva production
- superior cervical ganglion and the ECA nerve plexus
Describe the route of the infratemporal portion of the facial nerve as it exits the skull.
- exits the pons as 2 roots (sensory and parasympathetic motor)
- roots enter internal acoustic meatus and facial canal
- roots fuse to form geniculate ganglion
- greater petrosal nerve branches here
- facial nerve travels inferiorly giving 2 branches, nerve to stapedius and chorda tympani
- facial nerve exits skull via stylomastoid foramen
What are the 2 portions of the facial nerve?
- infratemporal portion
- extratemporal portion
Describe the route of the extratemporal portion of the facial nerve.
- exits skull via stylomastoid foramen
- 2 branches, posterior auricular and digastric branches
- main nerve enters parotid gland
What branches in the parotid plexus?
- temporal
- zygomatic
- buccal
- marginal mandibular
- cervical
What do the temporal branches of the facial nerve supply?
Muscles of temple, forehead and supraorbital area
What do the zygomatic branches of the facial nerve supply?
Muscles of infraorbital area, the lateral nasal area and the upper lip
What do the buccal branches of the facial nerve supply?
Muscles of the cheek, the upper lip and the corners of the mouth
What do the marginal mandibular branches of the facial nerve supply?
Muscles of the lower lip, chin and resorious.
What do the cervical branches of the facial nerve supply?
Platysma
What is Bell’s palsy?
Facial paralysis that usual affects both the upper and lower face
What causes Bell’s palsy?
- cause unknown
- may be viral infections
- paralysis an also be caused by dental anaesthesia
How do you treat Bell’s palsy?
- steroids
- anti-virals
- eye patch is important on the affected side to prevent injury to the eye
- can be treated surgically (with tendon or nerve from the leg) if long term
What are the surgical options for treatment of Bell’s palsy?
- sling to hold up side of mouth (using tendon from leg)
- gold weight within eyelid to assist with closing
How do tumours of the parotid gland affect the facial nerve?
- impinge on the nerve and cause palsy
- usually benign (70-80%)
- NB: majority of salivary gland cancers begin in the parotid
What nerve can be used as a graft if the facial nerve is damaged?
Great auricular nerve
What is mumps?
- viral infection that causes swelling of the parotid gland
- MMR vaccine protects against
