Temporomandibular Joint Question And Answers

Temporomandibular Joint

Question 1. Enumerate the ligaments of the temporomandibular joint and their functions.
Answer:

Ligaments of the temporomandibular joint:

• Fibrous capsule.
• Lateral ligament or temporomandibular ligament.
• Sphenomandibular ligament.
• Sytolomandibular ligament.

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Fibrous capsule Attachments:

• Above – Articular eminence.
• Circumference of the mandibular fossa
• Squamotympanic fissure
• Below- Neck of mandible.

Fibrous capsule Functions:

• It seals the joint space.
• It provides passive stability enhanced by local thickening and active stability from proprioceptive nerve endings.
• Lateral ligament

Lateral ligament:

Lateral ligament Attachments:

• Above – articular tubercle.
• Below – posterolateral aspect of the neck of the mandible.

Lateral ligament Functions:

• It seals the joint space.
• It provides passive stability enhanced by local thickening and active stability from proprioceptive nerve endings.

Lateral ligament Attachments:

• Above articular tubercle.
• Below – posterolateral aspect of the neck of the mandible.

Lateral ligament  Functions:

• It reinforces and strengthens the lateral part of the capsular ligament.
• It restricts the displacement of the mandible in three different planes.

Sphenomandibular ligament:

Sphenomandibular ligament Attachments:

• Superiorly spine of sphenoid.
• Inferiorly- lingula of mandibular foramen.

Sphenomandibular ligament Functions:

• It is an accessory ligament.
• It represents a remnant of Meckel’s cartilage.

Stylomandibular ligament Attachments:

• Above – lateral surface of the styloid process.
• Below the angle and adjacent part of the posterior border of the ramus of the mandible.

Stylomandibular ligament Functions:

• It is an accessory ligament.
• It represents the free border of the deep cervical fascia.

Question 2. Write briefly about the temporomandibular joint.
Answer:

Temporomandibular Joint Articular surfaces:

1. Upper articular surface formed by.

• Articular tubercle.
• Anterior part of mandibular fossa.

2. Lower articular surface formed by.

• Head of the mandibular fossa.

Temporomandibular Joint Ligaments:

• Fibrous capsule.
• Lateral ligament.
• Sphenomandibular ligament.
• Stylomandibular ligament.

Temporomandibular Joint Movements:

• Rotational movements – take place in the lower compartment of the joint.
• Gliding movements – take place in the upper compartment of the joint.

Temporomandibular Joint Blood supply:

• Branches from maxillary and superficial temporal arteries.
• Veins follow arteries.

Temporomandibular Joint Nerve supply:

• Auriculotemporal nerve.
• Massetric nerve.

Question 3. Mastication
Answer:

• It is the mechanical process that breaks up larger food particles into smaller pieces

Mastication Importance:

• Makes it easy for food to be swallowed
• Mixes food with the secretions of the salivary glands to soften it
• Increases the surface area of food particles to enable subsequent digestion
• Important for most fruits and raw vegetables because they contain undigestible cellulose membrane

Mastication Muscles of mastication:

• They help in mastication through their actions
• Muscles and their actions

Question 4. Histology of temporomandibular joint.
Answer:

• The articular disc is made up of type I collagen.
• The articular surfaces of the temporomandibular joint are covered with fibrous tissue.
• The capsule is lined on its inner surface by a synovial membrane.
• The synovial membrane lines the entire capsule with folds or villi of the membrane protruding into the joint cavity.
• The synovial membrane consists of two layers.

Cellular intima:

• It has one to four layers of synovial cells embedded in an amorphous, fiber-free intercellular matrix.

Vascular subintima:

• It is a loose connective tissue containing vascular elements along with scattered fibroblasts, macrophages, mast cells, fat cells, and some elastic fibers.
• This prevents the folding of the membrane.

Question 5. Articular capsule.
Answer:

• It is a fibrous, non-elastic membrane surrounding the joint.

Articular capsule Attachments:

• Above -Articular tubercle
• Circumference of the mandibular fossa
• Squamotympanic fissure
• Below-Neck of the mandible.

Articular capsule Histology:

• It consists of a dense collagenous membrane that seals the joint space and provides passive stability.
• It consists of increased local thickening in its walls and provides active stability from proprioceptive nerve endings in the capsule.
• The capsule is lined on its inner surface by a synovial membrane.
• The upper part of the capsule consists of fibrous and elastic tissue while the lower part consists of collagen fibers.

Question 6. Articular disc.
Answer:

• It is an oval fibrous plate that divides the joint into upper and lower compartments.
• The upper compartment permits gliding movements and the lower permits rotator as well as gliding movements.

Articular disc Surface:

• Superior concavoconvex.
• Inferior-concave.

Articular disc Histology:

• The periphery of the disc is attached to a fibrous capsule.
• It is composed of an anterior extension, anterior thick bond, intermediate zone, posterior thick band, and bilaminar region.
• The anterior portion of the disk fuses with the anterior wall of the capsule.
• Above it, it blends with the periosteum of the anterior slope of the articular eminence.
• Below it, it merges with the periosteum of the front of the neck of the condyle.

Question 7. Lateral pterygoid
Answer:

• The lateral pterygoid muscle has two heads:

Lateral pterygoid Origin:

1. Upper head
   • Infratemporal surface & crest of the greater wing of the sphenoid
2. Lower head
   • The lateral surface of the lateral pterygoid plate

Lateral pterygoid Insertion:

• Pterygoid fovea on the anterior surface of the neck of the mandible
• Anterior margin of articular disc of TMJ

Lateral pterygoid Nerve supply:

• A branch from the anterior division of a mandibular nerve

Lateral pterygoid Action:

• Depression of mandible
• Protrusion of mandible
• Act alternatively with others for side-to-side movements

Question 8. Medial pterygoid
Answer:

• Quadrilateral in shape
• Has two heads

Medial pterygoid Origin:

• Superficial head
• Tuberosity of maxilla
• Pyramidal process of palatine bone
• Deep head
• Medial surface of lateral pterygoid plate

Medial pterygoid Insertion:

• The roughened area on the Medial surface of the ramus of the mandible
• The angle of the mandible below & behind the mandibular foramen &mylohyoid groove

Medial pterygoid Nerve supply:

• Nerve to Medial pterygoid
• A branch from the main trunk of the mandibular nerve

Medial pterygoid Action:

• Elevates mandible
• Protrusion of mandible
• Alternate contraction during side-to-side movements

Question 9. Anterior belly of digastric
Answer:

Anterior belly of digastric Origin:

• Digastric fossa on the lower border of mandible close to symphysismenti

Anterior belly of digastric Insertion:

• Intermediate tendon

Anterior belly of digastric Nerve supply:

• Mylohyoid branch of the inferior alveolar nerve

Anterior belly of digastric Actions of digastric muscle:

• It depresses and retracts the chin in opening the mouth
• They pull hyoid bone upward and help in deglutition

Question 10. Functions of temporomandibular joint
Answer:

• TMJ helps with mandibular movements
• When the mouth is opened
• Two distinct motions occur at the joint
• The first motion is rotation around a horizontal axis through the condylar heads
• The second motion is a translation
• In it, the condyle and meniscus move together anteriorly beneath the articular eminence
• In closed-mouth position
• A thick posterior band of meniscus lies immediately above the condyle
• As the condyle translates forward, the thinner intermediate zone of the meniscus becomes articulating surface
• When the mouth is fully opened
• Condyle lie beneath the anterior band of the meniscus

Question 11. Masseter
Answer:

• Quadrilateral in shape
• Has two layers

Masseter Origin:

• Superficial layer
• Anterior 2/3rd of the lower border of the zygomatic arch
• Zygomatic process of maxilla
• Deep layer
• The deep surface of the zygomatic arch

Masseter Insertion:

• Upper & anterior part of the lateral surface of the ramus of the mandible
• Part of the Coronoid process

Masseter Nerve supply:

• Massetric nerve
• A branch from the anterior division of a mandibular nerve

Masseter Action:

• Elevates mandible
• Superficial fibers help in Protrusion
• Deep fibers help in the retraction of mandible