TMJ Anatomy and Dysfunction

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are the common etiologies of myofascial pain and dysfunction?

Nocturnal bruxism (correct)

Habitual clenching of the mouth (correct)

Frequent jaw surgeries

Chronic dehydration

What is a common consequence of bruxism related to TMJ?

Reduced pain in jaw movement

Improved muscle balance

Imbalance of forces in the masticatory muscles (correct)

Increased mandibular mobility

Which symptom can indicate muscle spasm of the muscles of mastication?

Relaxed jaw movement

Increased chewing strength

Decreased pain during eating

Lockjaw (correct)

Where can tumors affecting the muscles of mastication be located?

Masticator space Signup and view all the answers

How does uncomplicated jaw dislocation typically occur?

Forward direction Signup and view all the answers

What assists in the reduction of a dislocated jaw?

Pressing down on the molar teeth Signup and view all the answers

Which of the following is NOT typically associated with trismus?

An allergic reaction Signup and view all the answers

What anatomical features are involved in dislocation of the jaw?

Condyloid process and articular eminence Signup and view all the answers

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

Concavoconvex Signup and view all the answers

Which compartment of the temporomandibular joint allows for more freedom of movement?

Superior compartment Signup and view all the answers

What ensures the disc moves in sync with the head of the mandible?

Fibrous bands Signup and view all the answers

Which nerve predominantly supplies the joint capsule of the TMJ?

Mandibular division of the trigeminal nerve Signup and view all the answers

Which muscle is NOT considered one of the principal muscles of mastication?

Pectoralis major Signup and view all the answers

What is the primary function of the muscles of mastication?

Movement of the lower jaw Signup and view all the answers

Where does the temporalis muscle originate?

Temporal fossa Signup and view all the answers

What type of vascular supply is provided to the temporomandibular joint?

Both arterial and venous Signup and view all the answers

What type of joint is the temporomandibular joint (TMJ)?

Synovial joint Signup and view all the answers

Which bones articulate at the temporomandibular joint?

Mandible and temporal bone Signup and view all the answers

What is the function of the lateral temporomandibular ligament?

It limits posterior movement of the mandible Signup and view all the answers

Where does the sphenomandibular ligament attach?

From the spine of the sphenoid to the mandible Signup and view all the answers

What is the role of the articular disc in the TMJ?

It separates the upper and lower compartments of the joint Signup and view all the answers

Which ligament lies behind and medial to the temporomandibular joint?

Stylomandibular ligament Signup and view all the answers

What kind of tissue forms the capsule surrounding the TMJ?

Dense irregular connective tissue Signup and view all the answers

How many components make up the functioning joint of the temporomandibular system?

Two Signup and view all the answers

What is the primary action of the medial pterygoid muscle?

It elevates the mandible. Signup and view all the answers

Which nerve supplies the medial pterygoid muscle?

Mandibular nerve Signup and view all the answers

What is the primary role of the medial and lateral pterygoids working together on one side of the mandible?

Rotating the mandible forwards Signup and view all the answers

Where does the medial pterygoid muscle insert?

Medial surface and angle of ramus of mandible Signup and view all the answers

Which movement is facilitated by the alternating contraction of the medial and lateral pterygoids on both sides?

Grinding food Signup and view all the answers

What is the primary function of the temporalis muscle?

Elevates the mandible Signup and view all the answers

Which nerves supply the masseter muscle?

Masseteric nerve Signup and view all the answers

What action do the lateral pterygoid muscles perform when acting together?

Depress the mandible Signup and view all the answers

Which muscle is primarily responsible for powerful jaw closure?

Masseter Signup and view all the answers

What is the insertion point of the lateral pterygoid muscle?

Pterygoid fovea on the neck of the mandible Signup and view all the answers

Which part of the zygomatic bone does the superficial part of the masseter originate from?

Inferior border of zygomatic arch Signup and view all the answers

Which of the following actions do the posterior fibers of the temporalis muscle perform?

Retraction of the mandible Signup and view all the answers

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

Infratemporal surface of sphenoid bone Signup and view all the answers

Study Notes

Myofascial Pain and Dysfunction

Common causes include nocturnal bruxism, clenching, and whiplash injuries.

Temporomandibular Joint (TMJ) Dysfunction

Can result from an imbalance of forces within the muscles of mastication
Bruxism is a common cause of TMJ dysfunction
Muscle spasm of the muscles of mastication (trismus) can be a symptom of tumor or infection.

Jaw Dislocation

Uncomplicated dislocation occurs in a forward direction.
Upward dislocation can only occur with significant skull base damage.
Backward dislocation can only occur with damage to the external auditory canal and tympanic cavity

TMJ Anatomy

The TMJ is a synovial joint between the head of the mandible and the mandibular fossa.
The mandible is a single bone with a horseshoe-shaped body and vertical rami.
The cranium has a mandibular fossa on each side.
Movement at one TMJ results in movement on the opposite side.

TMJ Capsule

Composed of dense, irregular collagenous connective tissue.
Attached to the articular tubercle and the margins of the mandibular fossa, and below to the neck of the mandible.

TMJ Synovial Membrane

Lines the capsule in both the upper and lower cavities of the joint.

TMJ Ligaments

Lateral temporomandibular ligament: Limits posterior movement of the mandible, protecting the external auditory meatus.
Sphenomandibular ligament: Attached to the spine of the sphenoid bone and the lingula of the mandibular foramen. A remnant of the first pharyngeal arch.
Stylomandibular ligament: A band of thickened deep cervical fascia extending from the styloid process to the angle of the mandible.

TMJ Articular Disc

An oval plate of fibrocartilage that divides the TMJ into upper and lower compartments.
The upper surface is concavoconvex and the lower surface is concave.
The upper compartment allows movement, while the lower compartment is more firmly attached.
The disc is attached to the tendon of the lateral pterygoid muscle and the head of the mandible.

TMJ Nerve Supply

The joint capsule receives sensory innervation from the mandibular division of the trigeminal nerve (branches of the auriculotemporal nerve).
Additional innervation comes from the masseteric branch of the mandibular division of the trigeminal nerve.

TMJ Blood Supply

Vascular supply is provided by branches of the superficial temporal and maxillary arteries.

Muscles of Mastication

Temporalis: Elevates the mandible, retracts the mandible after protrusion.
Masseter: Elevates the mandible, aids in protrusion.
Medial pterygoid: Elevates the mandible, protrudes the mandible, rotates the mandible to the opposite side.
Lateral pterygoid: Depresses the mandible, protrudes the mandible, produces side-to-side movements with medial pterygoid.
All masticatory muscles are supplied by the mandibular division of the trigeminal nerve.

Temporalis Muscle

Fan-shaped muscle in the temporal fossa covered by the temporal fascia.
Origin: Floor of temporal fossa, deep surface of the temporal fascia.
Insertion: Coronoid process of the ramus of the mandible, anterior border of the ramus of the mandible.
Nerve Supply: Anterior and posterior deep temporal nerves.

Masseter Muscle

Thick quadrilateral muscle covering the lateral surface of the ramus of the mandible.
Origin: Superficial part - maxillary process of zygomatic bone, inferior border of the zygomatic arch (anterior 2/3). Deep part - deep/inferior surface of the zygomatic arch (posterior 1/3).
Insertion: Lateral surface of the ramus and angle of the mandible.
Nerve Supply: Masseteric nerve.

Lateral Pterygoid Muscle

Short, thick conical muscle in the infratemporal fossa.
Origin: Two heads; upper head - infratemporal surface and crest of the greater wing of the sphenoid bone; lower head - lateral surface of the lateral pterygoid plate.
Insertion: Pterygoid fovea on the front of the neck of the mandible, articular disc, and capsule of the TMJ.
Nerve Supply: Branch of the anterior division of the mandibular nerve.

Medial Pterygoid Muscle

Thick quadrilateral muscle in the infratemporal fossa.
Origin: Small superficial head - maxillary tuberosity, large deep head - medial surface of the lateral pterygoid plate.
Insertion: Posteroinferior part of the medial surface and angle of ramus of the mandible.
Nerve Supply: Nerve to the medial pterygoid.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers topics related to myofascial pain, TMJ dysfunction, and the anatomy of the temporomandibular joint. Explore the common causes, symptoms, and mechanisms of jaw dislocation, as well as the unique structure of the TMJ. Test your knowledge on this essential subject in dental and physical health.