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Questions and Answers
What is the type of joint that the TMJ is classified as?
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?
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?
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?
What is the function of the lateral pterygoid muscle when one muscle acts alone?
What is the characteristic of the articular surfaces of the TMJ?
What is the characteristic of the articular surfaces of the TMJ?
What is the articular surface of the TMJ below?
What is the articular surface of the TMJ below?
Which nerve supplies the masseter muscle?
Which nerve supplies the masseter muscle?
What is the origin of the temporalis muscle?
What is the origin of the temporalis muscle?
What is the function of the posterior fibers of the temporalis muscle?
What is the function of the posterior fibers of the temporalis muscle?
Where does the lateral pterygoid muscle insert?
Where does the lateral pterygoid muscle insert?
What happens when both lateral pterygoid muscles act together?
What happens when both lateral pterygoid muscles act together?
What is the function of the deep vertical fibers of the masseter muscle?
What is the function of the deep vertical fibers of the masseter muscle?
What is the origin of the lower head of the lateral pterygoid muscle?
What is the origin of the lower head of the lateral pterygoid muscle?
What happens when one lateral pterygoid muscle acts alone?
What happens when one lateral pterygoid muscle acts alone?
What is the shape of the articular disc's upper surface?
What is the shape of the articular disc's upper surface?
Where is the temporomandibular ligament attached above?
Where is the temporomandibular ligament attached above?
What is the function of the temporomandibular ligament?
What is the function of the temporomandibular ligament?
What type of tissue is the articular disc composed of?
What type of tissue is the articular disc composed of?
What is the shape of the temporomandibular ligament?
What is the shape of the temporomandibular ligament?
Where is the fibrous capsule attached below?
Where is the fibrous capsule attached below?
Which ligament is attached to the spine of sphenoid bone?
Which ligament is attached to the spine of sphenoid bone?
What is the primary action of the lateral pterygoid muscle in the TMJ?
What is the primary action of the lateral pterygoid muscle in the TMJ?
Which nerve is responsible for the nerve supply of the TMJ?
Which nerve is responsible for the nerve supply of the TMJ?
What is the direction of mandible dislocation?
What is the direction of mandible dislocation?
Which movement of the TMJ is done by the medial and lateral pterygoids of both sides acting alternately?
Which movement of the TMJ is done by the medial and lateral pterygoids of both sides acting alternately?
Which artery supplies blood to the TMJ?
Which artery supplies blood to the TMJ?
Which ligament is attached to the angle and posterior border of ramus of mandible?
Which ligament is attached to the angle and posterior border of ramus of mandible?
Which movement of the TMJ is done by the posterior horizontal fibers of temporalis?
Which movement of the TMJ is done by the posterior horizontal fibers of temporalis?
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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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