Muscles of Mastication Flashcards
What are the landmarks of the mandible?
condyle
coronoid process
angle
ramus
oblique line
mental foramen
mandibular foramen
mylohyoid line
alveolar process
lingula
body
sublingual fossa
What is the purpose of the mandible?
- Site for muscle attachments
- Foramina for passage of
neurovascular structures - Teeth in alveolar processes
What is the TMJ betweeen?
Mandibular fossa of temporal bone & condylar process of mandible
What type of joint is the TMJ?
Modified hinge (atypical) synovial joint
What are the articular surfaces of bone covered with?
fibrocartilage (not hyaline cartilage)
What seperates the joint and into what?
Fibrocartilaginous articular disc separating the joint into superior & inferior articular cavities
What are the ligaments of the TMJ and what do they connect?
- 2 extrinsic - sphenomandibular ligament, stylomandibular ligament. & 1 intrinsic - lateral
- Connect mandible to cranium
What does the spheomandibular ligament do?
Primary passive
support of the mandible
What does the lateral ligament do?
- Strengthens TMJ laterally
- With postglenoid tubercle prevent posterior dislocation
What is the most common injury to the TMJ?
anterior dislocation
What are main movements of the TMJ?
gliding
hinge and rotation
lateral (side to side)
What are the gliding movements and what muscles are they carried out by?
Protrusion - lateral pterygoid
Retraction - temporalis,
What cavity do gliding movements take place in?
between temporal bone and articular disc (superior cavity)
What are the hinge and rotational movements and what muscles are they carried out by?
Elevation - temporalis, masseter, medial pterygoid
Depression - gravity, digastric, geniohyoid and mylohyoid, lateral pterygoid
What cavity do hinge and rotation movements happen?
inferior
between head of mandible and articular disc
What muscles carry out lateral movements?
side to side - grinding/chewing
lateral pterygoid
medial pterygoid
What happens in anterior dislocation?
condyle dislocated anterior to articular tubercle
Where is the special visceral efferent of CNV located in brainstem?
motor nucleus in the pons
MOM
Where is the general somatic afferent of CNV in the brainstem?
to the mesencephalic, chief sensory & spinal nuclei in the midbrain, pons & medulla oblongata
respectively
What is the embryological orgins of the MOM?
1st pharyngeal arch
What are the attachements of the temporalis?
- Originates from temporal fossa & fascia (broad)
- Inserts at coronoid process of mandible (medial surface) & anterior border of ramus of mandible near last molar (narrow)
What are the actions and innervation of the temporalis?
- Retracts & elevates the mandible (assists in closing the mouth)
- Innervated by deep temporal nerves from anterior trunk of CN V3
What are the attachements of the masseter?
- Originates from maxillary process of zygomatic bone & anterior 2/3rd of inferior border of zygomatic arch (superficial head)
- Inserts at the angle & lateral surface of ramus of mandible (superficial head)
What are the layers to the masseter?
deep
middle
superficial
What is the innervation and action of the masseter?
- Innervated by masseteric nerve from anterior trunk of CN V3
- Elevates the mandible (powerful elevator!)
What must be removed to view the lateral/medial pterygoid?
body of mandible
What are the attachements of the medial pterygoid?
- Originates from medial surface of lateral pterygoid plate (deep head) & maxillary tuberosity & pyramidal process of palatine bone (superficial head)
- Inserts into medial surface of the ramus & angle of mandible
What are the actions and innervation of the medial pterygoid?
- Elevates the mandible & assists with lateral (side-to-side) movements
- Innervated by nerve to medial pterygoid from main trunk of CN V3
What are the heads of the lateral pterygoid?
upper
lower
What are the attachements of the lateral pterygoid?
- Originates from infratemporal surface of greater wing of sphenoid bone (upper head) & lateral surface of lateral pterygoid plate (lower head)
- Inserts on the front of the neck of the mandible (pterygoid fovea) (capsule of TMJ & articular disc)
What are the actions and innervation of the lateral pterygoid?
Protrudes the mandible, assists medial pterygoid with lateral (side-to-side) movements & depresses the mandible
Innervated by nerve to lateral pterygoid & buccal nerve from anterior trunk of CN V3
What muscles apart from MOM does CNV3 supply?
tensor tympani muscle in the middle ear and tensor palati ( via the branch to medial pterygoid);
mylohyoid and anterior belly of digastric (via its inferior alveolar branch)
What is the prime mover of depressing the mandible?
gravity
What is the prime mover of protruding the mandible?
lateral pterygoid
What muscles carry out elevation?
Temporalis, masseter & medial pterygoid
What muscles carry out depression?
Lateral pterygoid, suprahyoid & infrahyoid muscles
What muscles carry out protrusion?
Lateral pterygoid, masseter & medial pterygoid
What muscles carry out retrusion?
Temporalis (posterior oblique & near horizontal fibers)
What muscles carry out lateral movements?
grinding and chewing
Temporalis of same side, pterygoids of opposite side & masseter
What are primary symptoms of TMDs?
- Facial muscle pain
- Preauricular (TMJ) pain
- TMJ sounds: jaw clicking, popping,
catching, locking - Limited mouth opening
What are secondary symptoms of TMDs?
- Earache
- Headache
- Neckache
What are the phases of swallowing?
oral
pharyngeal
oesophageal
What happens in the oral phase and is it voluntary?
voluntary
bolus is formed in the oral cavity by the action of chewing
bolus pushed into oropharynx by tongue
When is the oral phase subdivided?
Subdivided into oral preparatory & transit phase when describing the swallowing of liquids including saliva
What happens in the pharyngeal phase and is it voluntary?
involuntary
- Superior pharyngeal constrictor contraction & soft palate elevation
- Pharyngeal elevation to receive food bolus (pharyngeal elevators)
- Food bolus pushed towards the oesophagus (pharyngeal constrictors)
- Epiglottis closes the laryngeal inlet protecting the airway (vocal folds also close for the same reason)
What is elevated/depressed in the pharyngeal phase and what happens to respiration?
- Simultaneous elevation of the pharynx & larynx (pharyngeal elevators) for airway protection
- Elevation of hyoid (suprahyoid muscles)
- Depression of hyoid & larynx (infrahyoid muscles) following elevation
- Respiration temporarily suspended but recommences after pharyngeal & laryngeal depression
What happens in the oesophageal phase and is it voluntary?
involuntary
- As the inferior pharyngeal constrictor contracts the upper oesophageal sphincter relaxes allowing the food bolus into the oesophagus
- Peristaltic movements move the food bolus towards the stomach
What are the main nerves of the infratemporal fossa?
mandibular
inferior alveolar
lingual
buccal
chorda tympani
otic ganglion
What are the muscles of the infratemporal fossa?
inferior part of temporalis
lateral pterygoid (superior and inferior heads)
medial pterygoid
What nerves are part of the posterior trunk of CNV3 and which are sensory/motor?
lingual nerve (sensory)
IAN (mixed)
auriculotemporal (sensory)
What artery is between the auriculotemporal nerve and otic ganglion?
middle meningeal artery
What encircles the MMA?
auriculotemporal nerve
What does the largest branch of the auriculotemporal nerve supply?
sensory fibres to auricle & temporal region
Where does the auriculotemporal nerve send sensory fibres to?
TMJ
What does the auriculotemporal nerve pass to the parotid gland?
Passes postsynaptic parasympathetic secretomotor fibres to parotid gland (from otic ganglion)
Where does the IAN enter and what does the mental nerve supply?
- Enters mandibular foramen & passes through mandibular canal, forming inferior dental plexus (supplies mandibular teeth)
- Mental nerve passes through mental foramen; supplies skin of lower lip & chin, gingiva of mandibular incisors
What does the lingual nerve supply, what does it pass and what is it joined by?
- Sensory to anterior 2/3rds of tongue, floor of mouth, lingual gingivae
- Passes medial and inferior to 3rd molar tooth
- Joined by chorda tympani nerve within infratemporal fossa
What nerves supply general sensation to the mandibular teeth?
inferior alveolar nerve
incisive branch of IAN
What nerves supply general sensation to the lower gingivae?
lingual nerve
buccal nerve
mental nerve
What are the 3 parts of the maxillary artery?
1st - mandbilar
2nd - pterygoid
3rd - pterygopalatine
What are the important branches of the mandibular branch of maxillary artery?
middle meningeal
inferior alveolar
What are the important branches of the pterygoid branch of maxillary artery?
masseteric
deep temporal
buccal
What are the important branches of the pterygopalatine branch of maxillary artery?
posterior superior alveolar
infra-orbital
descending palatine
