Parotid bed and temporo-masseteric region (A17) Flashcards
tempero-masseteric region
- region that encompasses temporalis muscle and masseter muscle
- clinically significant area when surgically accessing fractured zygomatic bone/arch (relevant to temporalis muscle) and for botox (relevant to masseter muscle)
swelling of parotid gland
- during mealtimes when the salivary duct gets blocked, leads to salivary calculi and swelling of side of face (due to swelling of parotid gland)
- when inserting needle into inferior alveolar nerve during block injection to block action potentials, can accidently numb other regions
salivary glands
- 3 pairs of major salivary glands (including parotid gland)
- also minor salivary glands located in oral mucosa
parotid glands
-paired major salivary gland (produce saliva)
type of secretion from parotid gland
- serous secretions
- contribute to saliva
parotid fascia/capsule
-derived from investing layer of deep cervical fascia, ascends/extends up to zygomatic arch and capsulizes parotid gland
location of parotid glands
- sits just anterior and below earlobe
- anterior border sits next to posterior border of masseter muscle
- posterior margin sits on anterior border of SCM
masseter muscle
muscle of mastication
buccinator muscle
muscle of facial expression
nerve supply to masseter muscle
mandibular division of trigeminal/CNV3/CNVc
nerve supply to buccinator muscle
facial nerve
parotid duct
- drains via parotid papilla on the buccal mucosa lining the inside of the cheek opposite the upper second molar tooth
- crosses superficial part of masseter and pierces buccinator
- tube that saliva travels in from parotid gland to reach oral cavity
stimulation of saliva production
- thought/smell/taste of food
- pain in/around the mouth (ie.teething babies)
nerve innervation of glands
glands=organs, therefore they are innervated by autonomic nervous system
response to the stimulus of saliva production
- nervous system responds to produce saliva
- autonomic control (parasympathetic/sympathetic)
type of saliva produced by sympathetics
- ‘sticky’ saliva
- mouth feels ‘dry’ in the fight or flight response
type of saliva produced by parasympathetics
- ‘runny saliva’
- rest and digest
- due to parasympathetic secretomotor nerve supply (glossopharyngeal nerve, CN IX, supplies the parotid gland with its parasympathetic secretomotor nerves)
parasympathetic secretomotor supply to parotid gland
glossopharyngeal nerve (CNIX)
parasympathetic secretomotor nerves
supply lacrimal gland and salivary gland
parasympathetic nerves
- CRANIOSACRAL outflow (comes from cranial nerves and sacral spinal nerves)
- cranial nerves 3(occulomotor), 7(facial), 9(glossopharyngeal) and 10(vagus), supply majority of viscera of the body (from the lacrimal gland to the mid gut)
- sacral spinal nerves supply from around the area of the mid gut- down
where does the glossopharyngeal nerve exit the base of the skull
jugular foramen
synapse of glossopharyngeal nerve (CNIX)
- preganglionic parasympathetic fibres travel in the lesser petrosal branch of the glossopharyngeal nerve and extend out to ganglion (otic ganglion) where they synapse
- post ganglionic fibres hitchhike a ride on the auriculotemporal nerve (sensory branch of CNV3) to supply the parotid gland
salivary calculus
- stone formed due to mineralization of saliva
- causes blockage of parotid duct
- saliva is then backed up into parotid gland causing swelling of gland/face
tympanic plexus
- The tympanic nerve arises as the glossopharyngeal nerve travels through the jugular foramen, it forms the tympanic plexus
- tympanic plexus – a network of nerves that provide sensory innervation to the middle ear, internal surface of the tympanic membrane and Eustachian tube
- In the tympanic cavity, the tympanic nerve (a branch of CN IX) divides into branches which form the tympanic plexus.
- This tympanic plexus gives off:
(1) the lesser petrosal nerve
(2) the Deep branch (small deep petrosal nerve) to join the greater petrosal nerve
(3) branches to the tympanic cavity
location of otic gangion
-sits medial/deep to CNV3(mandibular division of trigeminal) after it passes through the foramen ovale
structures within parotid gland fascia/capsule
Lateral to medial (N-V-A):
- Facial nerve (CNVII)
- Retromandibular vein.
- External Carotid artery.
- Parotid lymph nodes (scattered, deep cervical lymph nodes/lymph drainage)
retromandibular vein
superficial temporal vein joins with maxillary vein to form retromandibular vein within the body of the parotid gland
facial nerve(CNVII) in relation to parotid gland
- enters posterior aspect of parotid gland and divides into its 5 terminal branches
- in order to visualize branches of facial nerve which sit on top of the deep part of the carotid gland you have to remove superficial part of the gland
external carotid artery in relation to parotid gland
enters inferior border of parotid gland to give superficial temporal artery and maxillary artery (2 terminal branches of external carotid artery which branch within body of parotid gland)
route CNVII (facial nerve) takes exiting skull
-before exiting the skull it exits the cranial cavity via the internal acoustic meatus, travels through the petrous part of the temporal bone before rerouting and exiting the stylomastoid foramen (between styloid and mastoid processes) before dividing into its 5 terminal branches
branches of facial nerve
- posterior auricular
- temporal
- zygomatic
- buccal
- mandibular
- cervical
- > posterior auricular branches off first, before the facial nerve enters the parotid gland where it branches into its 5 terminal branches (To Zante By My Car)
area supplied by posterior auricular nerve
- branch of facial(CNVII) before it enters parotid gland
- travels posterior to ear to supply posterior auricular muscles
(area supplied by) temporal nerve
- 1st branch of facial after it divides within parotid gland
- supplies temporal region
(area supplied by) zygomatic nerve
- 2nd branch of facial after it divides within parotid gland
- supplies quadratus superioris region
(area supplied by) buccal nerve
- 3rd branch of facial after it divides within parotid gland
- supplies buccinator
(area supplied by) mandibular nerve
- 4th branch of facial after it divides within parotid gland
- supplies angle of mandible
(area supplied by) cervical nerve
- 5th branch of facial after it divides within parotid gland
- supplies platysma muscle in neck
parotid bed
structures/borders that the gland lies on medially:
- styloid process of temporal bone (medial side of parotid gland/ deep surface of gland associated here)
- sternocleidomastoid muscle (posterior side of parotid gland lies here)
- mandibular ramus(medial and lateral sides of gland associated here as parotid gland wraps round the ramus)
- stylohyoid and posterior belly of digastric (medial) (deep surface of gland associated with these 2 muscles)
- masseter muscle (anterior part of gland lies here)
how can local anesthetic injection/inferior nerve block cause drooping of the face
- whilst performing dental block/numbing inferior alveolar nerve that travels in the mandibular ramus down the body of the mandible, dentist must be careful not to numb structures within parotid gland (such as the facial nerve CNVII which runs between the deep and superficial part of the parotid gland) as the parotid gland wraps round the mandibular ramus therefore it is in close proximity
- misplacement of local anaesthetic injection can numb the facial nerve which can cause iatrogenic reversible paralysis of the muscles of facial expression therefore causing drooping of the face
iatrogenic
damage caused by practitioner/surgeon/dentist
bones that contribute to the zygomatic arch
- zygomatic bone anteriorly (temporal process of zygomatic bone)
- temporal bone posteriorly (zygomatic process of temporal bone)
- zygomatic arch sits superficially therefore is easily fractured
temporalis fascia
overlies temporalis muscle
-attaches to superior temporal line superiorly and zygomatic arch inferiorly
which structures run across the superficial temporal line
- superficial temporal artery and vein
- auriculotemporal nerve (sensory branch of CNV3)
temporalis muscle
- jaw closing muscle
- extends from coronoid process of mandible up to inferior temporal line leaving an anatomical space between muscle and temporalis fascia
inferior attachment for temporalis muscles tendon
coronoid process of the mandible
superior attachment for temporalis muscles tendon
inferior temporal line
gillies approach to the fractured zygomatic bone/arch
- incision is made at the level of skin
- enters anatomical space between temporalis muscle and temporalis fascia (temporalis fascia extends more superiorly than the muscle does)
- non invasive way of accessing the zygomatic arch
use of botox in tempero-masseteric region
- irreversible blockage of the skeletal muscle neuromuscular junction- leads to atrophy (wasting) of the muscle fibres
- can be used to eliminate forehead muscles
- can also be used to bring master muscle back to normal size after hypertrophy/enlargement of masseter muscle (jaw closing muscle)
botox
- botulinum toxin
- blocks neuromuscular junction of skeletal muscle
masseter muscle
jaw closing muscle
attachments of masseter muscle (jaw closing muscle/muscle of mastication)
-area of masseteric attachment to mandible extends from ramus/angle of mandible to zygomatic arch
blood and nerve supply to masseter muscle
- via neuromuscular bundle which passes into the deep surface of masseter muscle via the coronoid notch of the mandible (notch between coronoid process and condylar head of mandible)
- nerve supply within bundle = CNVc/mandibular division of trigeminal
- blood supply within bundle = maxillary artery
