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oral bio > TMJ > Flashcards

TMJ Flashcards

1
Q

What is the TMJ?

A

mandibular articulation, a bilateral joint that permit the mandible to move as a unit with two functional movement gliding and hinge movements

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2
Q

What is the TMJ formed of?

A
  • mandibular condyle
  • mandibular fossa and articular eminence
  • articular disc
  • articular capsule
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3
Q

What are the movements of TMJ?

A
  • hinge
  • translatory (gliding)
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4
Q

What is the hinge movement of the TMJ?

A

in the inferior portion of the joint between the head of the condyle and the lower surface of the disc

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5
Q

What is the translatory (gliding) movement of the TMJ?

A

in the superior part of the joint ,as the disc and the condyle transverse anteriorly along the tubercle to provide anterior and inferior movement of the mandible

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6
Q

What is the TMJ divided into according to the articular disc?

A
  • upper compartment
  • lower compartment
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7
Q

What are the characteristics of the upper compartment of the TMJ?

A
  • between the upper part of the disc and the borders of the temporal bone
  • larger than the lower compartment since upper articular surface is wider
  • helps in for the gliding movement
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8
Q

What are the characteristics of the lower compartment of the TMJ?

A
  • between the lower part of the disc and the mandibular condyle
  • smaller than the lower compartment
  • helps in the joint hinge movement of the condyle during movement
  • synovial membrane is attached above the glenoid fossa and articular eminence and below to the articular margin of the head of the condyle
  • at the sides, the capsule is strengthened by collateral ligaments of which the temporomandibular ligament is the strongest
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9
Q

What are the TMJ ligaments?

A
  • temporomandibular ligaments
  • stylomandibular ligament
  • sphenomandibular ligament
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10
Q

What is the attachment of temporomandibular ligament?

A

attached above to the temporal bone and below to lateral surface of posterior border of neck of mandible

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11
Q

What is the stylomandibular ligament attached to?

A

attached to styloid process and the posterior border
of the ramus

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12
Q

What is the attachment of sphenomandibular ligamnt?

A

between spin of sphenoid bone and lingual of
mandible

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13
Q

What are the accessory ligaments of TMJ?

A
  • stylomandibular ligament
  • sphenomandibular ligament
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14
Q

What is the function of ligaments?

A

limits the movement of the mandible, and prevent its movement beyond the articular eminence

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15
Q

What are the charactristics of the mandibular condyle?

A
  • formed of cancellous bone covered by a thin layer of compact bone
  • the bone trabeculae of the spongy bone radiates from the neck of the condyle and reach the cortex at right angle (thus giving maximal
    strength to the condyle)
  • the condyle is covered by a fibrous layer, the fibrous connective tissue is formed of:
  • superficial layer is formed of strong collagenous fibrous bundles and fibroblast and few chondrocytes which increase by age
  • deep layer is rich of chondroid cells and undifferentiated cells as long as the growing cartilage is present in condyle and few in this collagenous fibers
  • chondrocytes may be present and increase by age
  • by age, the wide marrow spaces will decrease by the marked thickening of bone trabeculae
  • also by age, the red marrow spaces may be replaced by fatty marrow
  • during the period of growth, a layer of hyaline cartilage lies underneath the fibrous covering during the period of growth
  • it serves as an active growth center till the age of 21 years, and remains may remain till old age
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16
Q

What are the characteristics of mandibular fossa and articular eminence?

A
  • formed of a layer of compact bone
  • the articular eminence is formed of spongy bone covered with a thin layer of compact bone
  • the articular fossa is formed of a thin layer of compact bone
  • the fibrous covering is thin at the fossa and thick over the eminence, it is arranged in three layers:
  • inner zone: the fibers are arranged at a right angle to the bony surface ( in adults, it could show a thin layer of calcification)
  • outer zone: the fibers run parallel to the bony surface
  • intermediate layer: a small transitional zone of Isolated flat fibroblasts situated on the surface with long flat cytoplasmic process
17
Q

What are the characteristics of articular disc?

A
  • oval fibrous biconcave disc
  • its upper surface is concave- convex to fit the articular eminence and fossa of the temporal bone
  • its lower surface is concave to fit the head of the condyle
  • from behind of the disc, divided into:
  • ascending limb: attached to the anterior surface of tympanic fissure
  • descending limb: attached to the neck of the condyle
  • unlike the rest of the disc, the loose posterior part is vascularized and covered with synovial membrane but this membrane is not found on weight bearing
    regions of the disc
  • central and anterior region of disc is covered with fibrous CT devoid of blood vessels or nerves
18
Q

What is the histology of articular disc?

A
  • formed of dense avascular fibrous tissue
  • the fibers are straight and
    tightly packed and are parallel to the surface on the borders and in the middle they are interlacing
  • few elastic fibers may be present
  • fibroblasts with elongated cytoplasmic process are present
  • chondrocytes may be found with advancing age
19
Q

What is the articulating capsule?

A

a fibrous sac attached superiorly to the temporal bone (fossa and
eminence) and inferiorly to the neck of condyle

20
Q

What is the histology of articulating capsule?

A
  • ccapsule consists of two layers:
  • oouter fibrous layer where Its lateral part thickened to form tempro-mandibular ligament
  • inner synovial layer (synovial membrane), is a thin layer
    of connective tissue rich of blood supply and lined the entire capsule with folds or villi protruding into the joint cavity
  • by EM , it has two types of synovial cells:
  • type A (light) which secrets hyloronic acid
  • type B (dark) produce protein rich secretion
  • the synovial membrane is rich in blood vessels and lymphatics
21
Q

What are the characteristics of synovial fluid?

A
  • produced by the synovial membrane cells
  • formed of viscous fluid (formed of plasma with added protein and mucin), containing varying types of cells (monocytes, lymphocytes and occasional polymorphnuclear leukocytes and macrophages)
22
Q

What are the functions of synovial fluid?

A
  • provide a lubrication for the joint surfaces to reduce the erosion during joint function
  • provide nutrition to the disc and the articular surfaces
  • responsible for the removal of foreign material (phagocytosis), Innervations and blood supply
23
Q

What is the nerve supply of TMJ?

A

trigeminal nerve

24
Q

What are the ae changes of TMJ?

A
  • flattening of the condyle .
  • absence of cartilaginous zone of condyle
  • fibrous cover of condyle become thicker
  • osteoporosis for the condylar bony part.
  • articular disc become thinner and could show hyalinization
  • walls of blood vessels become thicker
  • nerves decreased in number
  • decrease of the synovial fluid in the TNJ cavity

oral bio (5 decks)

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