Muscles of Mastication-pp2 Flashcards
What is the origin, insertion, function and innervation of the MASSETER muscle?
Ori:
-Superficial Part: Anterior part of lower Zygomatic arch
-Deep part: Median surface of zygomatic arch
Ins: Angle of the mandible, lateral parts of coronoid process and ramus of the mandible.
Fun: Elevation of mandible
Inn: Masseteric nerve of V3
What differentiation in function is there between the superficial and deep fibers? (Think of their orientation of origination and this should make sense)
Superficial: Contribute to PROTRUSION of the mandible
Deep: Contribute to RETRUSION of the mandible
The masseter also contributes to ipsilateral excursion. What does this mean?
Ipsilateral excursion happens when contraction of muscles on one side cause the jaw to move to that side. Contraction of Right masseter draws the mandible to the Right and vice versa.
What is the origin, insertion, function and innervation of the TEMPORALIS muscle?
Ori: Inferior Temporal Line, Tempralis Fossa, and the temporalis fascia
Ins: Coronoid process and ramus of mandible
Fun:
-Ant. & Middle Fibers: Initial Mandibular Elevation
-Posterior Fibers: Retrusion (retraction) of mandible
Inn: Deep Temporal Branches of V3
Which two muscles of mastication lie within the intratemporal fossa?
- Lateral Pterygoid
2. Medial Pterygoid
What two muscles of mastication make up the PTERYGOMASSETERIC SLING?
The medial pterygoid and massteric muscle wrap around the angle of the mandible forming a sling like apparatus.
What is the origin, insertion, function and innervation of the MEDIAL PTERYGOID muscle?
Ori: Medial surface of the lateral pterygoid plate, pyramidal process of palatine bone, and a small slip from tuberosity of the maxilla.
Ins: Medial surface of the ramus and the lower angle of the mandible.
Fun: Mandibular elevation & assists lateral pterygoid with mandibular protrusion.
Inn: Medial pterygoid nerve of V3
The medial & lateral pterygoid muscles are involved in contralateral excursion of the mandible. What does this mean?
The mandible moves in the opposite direction of unilateral contraction. If RIGHT medial pterygoid contracts the mandible moves LEFT and vice versa
What is the origin, insertion, function and innervation of the LATERAL PTERYGOID muscle?
Ori:
-Superior Head: Greater wing of sphenoid bone, near the inferior orbital fissure
-Inferior Head: Lateral surface of lateral plate
Ins: Anterior neck of mandibular condyle, anterior portions of meniscus (disk) and articular capsule of TMJ
Fun: Mandibular (and articular disk) protraction
Inn: Lateral pterygoid nerve of V3
Masticatory muscels are derived from which developmental arch? What nerve innervates this developmental arch? What is unique about the branch that innervates the muscles of mastication.
First arch, which is innervated by the trigeminal nerve. Note: All masticatory muscle innervated by the mandibular branch of the trigeminal. V3. This is the ONLY branch of CN V to contain SVE fibers.
What hole in the skull does CNV3 exit from? Where do the nerves of the muscles of mastication arise from?
Foramen Ovale. The V3 then branches in the infratemporal fossa into the specific nerves that innervate the muscles of mastication (NOTE: generally named after the muscles they innervate!)
A lesion of the SVE fibers in CN V3 will produce deviation of the jaw to the side of the lesion when the mandible is PROTRUDED against resistance. Why?
B/c the lateral pterygoid is activated during protrusion and the lateral pterygoid is subject to contralateral movement during unilateral activation. Thus, if an injury causes only one side to fire, the mandible will move away from that side.
The muscles of mastication receive their blood supply from where? What is the specific part and where does it branch/arise from?
The PTERYGOID part of the maxillary artery that arises as the artery crosses the infratemporal fossa en route to the pterygomaxillary fissure
