Anatomy of Temporalis Muscle

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Questions and Answers

What is the type of joint that the TMJ is classified as?

Mono-axial hinge joint

Bi-axial condylar synovial joint (correct)

Uni-axial pivot joint

Tri-axial ball-and-socket joint

What is the function of the medial pterygoid muscle when both muscles act together?

Protrude and deviate the mandible to the same side

Elevate and retract the mandible

Elevate and protrude the mandible (correct)

Depress and protrude the mandible

Where does the medial pterygoid muscle insert into?

Articular tubercle of temporal bone

Medial surface of lateral pterygoid plate

Medial surface of angle and ramus of mandible, below the mandibular foramen (correct)

Lateral surface of mandibular fossa

What is the function of the lateral pterygoid muscle when one muscle acts alone?

Protrude and deviate the mandible to the opposite side Signup and view all the answers

What is the characteristic of the articular surfaces of the TMJ?

Covered by white fibrocartilage Signup and view all the answers

What is the articular surface of the TMJ below?

Head (condylar process) of mandible Signup and view all the answers

Which nerve supplies the masseter muscle?

Masseteric nerve Signup and view all the answers

What is the origin of the temporalis muscle?

Inferior temporal line Signup and view all the answers

What is the function of the posterior fibers of the temporalis muscle?

Retraction of the mandible Signup and view all the answers

Where does the lateral pterygoid muscle insert?

Front of the neck of mandible Signup and view all the answers

What happens when both lateral pterygoid muscles act together?

Protrusion and depression of the mandible Signup and view all the answers

What is the function of the deep vertical fibers of the masseter muscle?

Elevation of the mandible Signup and view all the answers

What is the origin of the lower head of the lateral pterygoid muscle?

Lateral surface of the lateral pterygoid plate Signup and view all the answers

What happens when one lateral pterygoid muscle acts alone?

Protrusion of the mandible to the opposite side Signup and view all the answers

What is the shape of the articular disc's upper surface?

Concavo-convex Signup and view all the answers

Where is the temporomandibular ligament attached above?

Root of zygomatic arch Signup and view all the answers

What is the function of the temporomandibular ligament?

Supports the joint Signup and view all the answers

What type of tissue is the articular disc composed of?

Dense avascular fibrocartilage Signup and view all the answers

What is the shape of the temporomandibular ligament?

Triangular Signup and view all the answers

Where is the fibrous capsule attached below?

Neck of mandible Signup and view all the answers

Which ligament is attached to the spine of sphenoid bone?

Spheno-mandibular ligament Signup and view all the answers

What is the primary action of the lateral pterygoid muscle in the TMJ?

Depression of the mandible Signup and view all the answers

Which nerve is responsible for the nerve supply of the TMJ?

Auriculotemporal nerve and Mandibular nerve Signup and view all the answers

What is the direction of mandible dislocation?

Only forwards Signup and view all the answers

Which movement of the TMJ is done by the medial and lateral pterygoids of both sides acting alternately?

Side-to-side movement Signup and view all the answers

Which artery supplies blood to the TMJ?

Maxillary artery and superficial temporal artery Signup and view all the answers

Which ligament is attached to the angle and posterior border of ramus of mandible?

Stylo-mandibular ligament Signup and view all the answers

Which movement of the TMJ is done by the posterior horizontal fibers of temporalis?

Retraction Signup and view all the answers

Study Notes

Temporalis Muscle

Origin: inferior temporal line, floor of temporal fossa, and temporal fascia
Insertion: tip and medial surface of coronoid process of mandible, and anterior border of ramus of mandible
Nerve supply: 2 deep temporal nerves, from anterior division of mandibular nerve
Action: elevation of mandible to close the mouth (antigravity) by anterior (vertical) fibers, and retraction of mandible by posterior (horizontal) fibers

Masseter Muscle

Origin: superficial oblique fibers from lower border of zygomatic arch, deep vertical fibers from inner surface of zygomatic arch
Insertion: lateral surface of ramus of mandible
Nerve supply: masseteric nerve, from anterior division of mandibular nerve
Action: elevation of mandible to close the mouth (antigravity) by deep vertical fibers, and protrusion of mandible by superficial oblique fibers

Lateral Pterygoid Muscle

Origin: upper head from infratemporal surface and crest of the greater wing of sphenoid, lower head from lateral surface of the lateral pterygoid plate
Insertion: into the front of neck of mandible (pterygoid fovea), as well as the capsule and articular disc of the temporomandibular joint
Nerve supply: branch from the anterior division of mandibular nerve
Action: protrusion and depression of the mandible to open the mouth, deviation of mandible to opposite side when one muscle acts alone, and side-to-side movement when both muscles act alternately

Medial Pterygoid Muscle

Origin: superficial head from maxillary tuberosity, deep head from medial surface of lateral pterygoid plate
Insertion: into medial surface of angle and ramus of mandible, below the mandibular foramen
Nerve supply: branch from the main trunk of the mandibular nerve
Action: elevation and protrusion of the mandible when both muscles act together, deviation of mandible to opposite side when one muscle acts alone, and side-to-side movement when both muscles act alternately

Temporomandibular Joint (TMJ)

Type: bi-axial condylar synovial joint
Articular surfaces: head (condylar process) of mandible below, and mandibular fossa and articular tubercle of temporal bone above
Articular surfaces are covered by white fibrocartilage with collagen fibers predominating and few cartilage cells
Capsule: attached above to margins of mandibular fossa and articular eminence, and below to neck of mandible, with lateral thickening forming temporomandibular ligament
Articular disc: oval plate of dense avascular fibrocartilage dividing joint cavity into upper and lower compartments, with upper surface concavo-convex and lower surface concave, and periphery attached to fibrous capsule all-around

Ligaments of TMJ

Temporomandibular ligament: triangular ligament on lateral aspect of the joint, attached above to root of zygomatic arch and below to lateral aspect of neck of mandible, supporting the joint
Stylo-mandibular ligament: cord-like ligament on posterior aspect of the joint, attached above to anterior aspect of styloid process near its tip and below to angle and posterior border of ramus of mandible
Spheno-mandibular ligament: cord-like ligament on medial aspect of the joint, attached above to spine of sphenoid bone and below to lingula of mandible

Movements of TMJ

Depression (opening of mouth): combined movements of hinging and gliding, done by lateral pterygoid muscle assisted by gravity and other muscles
Elevation (closure of mouth, occlusal position): done by medial pterygoid, temporalis, and masseter of both sides
Protrusion (forward movement): done by medial and lateral pterygoids of both sides, with little effect by superficial fibers of masseter
Retraction (backward movement): done by the posterior horizontal fibers of temporalis
Side-to-side (grinding or chewing movement): done by medial and lateral pterygoids of both sides acting alternately

Nerve Supply and Blood Supply of TMJ

Nerve supply: auriculotemporal nerve and masseteric nerve (from mandibular nerve)
Blood supply: maxillary artery and superficial temporal artery (from external carotid artery)

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Description

Learn about the origin, insertion, nerve supply, and action of the Temporalis Muscle, a crucial facial muscle involved in mandible movement.