Muscles Of Mastication Flashcards
Which branchial arch do the muscles of mastication derive from?
The first pharyngeal arch - mandibular arch
What nerve supplies the muscles of mastication?
Mandibular division of trigeminal CNV3
What attaches to the superior temporal line?
Temporal fascia
Where does the temporalis originate?
Inferior temporal line
Describe the fibres of the temporalis
Posterior fibres of temporalis run more horizontally than the anterior fibres which are running more vertically. These fibres come together to form a tendon which inserts onto the coronavirus process of the mandible.
Function/action of separate temporalis posterior and anterior fibres
Vertical anterior fibres shorten to pull the mandible up = elevation
Horizontal posterior fibres shorten to pull the mandible back = retraction
Also aids in lateral excursion
Clinical implications of the temporalis going quite far down the mandible?
Goes very close to mandibular molars, so implications in denture fittings. E.g., if temporalis fits too anteriorly then it can dislodge dentures.
Innervation of temporalis
Anterior and posterior deep temporal branches of CNV3
Blood supply to temporalis
Deep temporal arteries
What are the 2 parts of the masseter and how do their fibres go?
Larger superficial head - fibres to posterior-inferiorly, aids in mandible protrusion
Smaller deeper head - fibres go more vertically
What do both parts of the masseter aid in?
Elevation of mandible, powerfully closing mouth. Aid in lateral excursion.
(superficial part helps protrude the mandible)
Origin and insertion of masseter
Origin: zygomatic arch
Insertion: lateral ramus and angle of the mandible
Innervation of masseter
Masseteric branch of CNV3 (anterior division)
Action of the lateral pterygoid
Lateral pterygoid muscles act to bring the condylar head of the mandible forward by protrusion and then rotation to depress the mandible.
Origin and insertion (and main function) of lateral pterygoid superior head
Origin: greater wing of sphenoid
Insertion: capsule and articular disc of TMJ
Action: protrusion
Origin and insertion (and main function) of lateral pterygoid inferior head
Origin: lateral surface of lateral pterygoid plates
Insertion: pterygoid fovea on neck of condylar process of mandible
Action: depression
Innervation of lateral pterygoids
Nerve to lateral pterygoid, anterior division of CNV3
Origin of medial pterygoid superficial head
Origin on maxillary tuberosity (posterior aspect of maxilla) and pyramidal process of palatine bone
Origin of medial pterygoid deep head
Origin on medial surface of lateral pterygoid plate
Insertion of the medial pterygoid
Superficial and deep heads come together to form a tendon and insert onto the medial surface of the angle of the mandible.
Actions of the medial pterygoids
Elevation, protrusion, lateral excursion
Innervation of medial pterygoids
Medial pterygoid nerve from main trunk of CNV3
Summary of muscles causing depression, elevation, retraction and protrusion of the mandible
Depression: lateral pterygoids, digastric, mylohyoid, geniohyoid
Elevation: temporalis, masseter, medial pterygoid
Retraction: posterior fibres of temporalis, deep part of masseter, geniohyoid and digastric
Protrusion: lateral pterygoid assisted by medial pterygoid and masseter
What happens in dissolution of the TMJ?
Condylar head comes out of the mandibular fossa, anterior to the articular tubercle.
