The document summarizes key anatomical structures and biomechanics of the temporomandibular joint (TMJ). It describes the TMJ's articular surfaces, discs, ligaments, blood supply, innervation, and the muscles involved in mastication. It discusses the different movements of the mandible during opening/closing, translation, and grinding. Clinical considerations include disc displacement and dislocation of the TMJ.

1. Temporomandibular joint
Muscles and mechanism of mastication
Muscles of facial expression
Mark Kozsurek, M.D., Ph.D.
mark@kozsurek.hu
EM I., 03/12/2018

2. Probably you’ve already seen in the dissection room...
Or will see soon...
coronoid process
condylar process
head or condyle of the mandible
pterygoid fovea
masseteric tuberosity
pterygoid tuberosity

3. mandibular fossa
articular eminence
petrotympanic fissure
(of Glaser)
articular eminence
mandibular fossa
petrotympanic fissure
(of Glaser)

4. Temporomandibular joint (TMJ)
mandibular fossa,
articular tubercle
mandibular condyle
ARTICULAR DISC
(made of fibrocartilage)
TMJ consists of two compartments: the discotemporal and discomandibular joints.
Note, that instead of hyalin cartilage all the articular surfaces are covered by fibrocartilage!

5. superior retrodiscal lamina
(elastic fibres)
inferior retrodiscal lamina
(collagen fibres)
• articular disc is thicker anteriorly and
posteriorly
• anterior border of the disc is in contact
with the upper insertion of the superior
belly of the lat. pterygoid muscle
• position of the disc is determined by the
superior part of lat. pterygoid muscle and
the elastic fibres of sup. retrodiscal lamina

6. AE: articular eminence
AB: anterior band
IZ: intermediate zone
PB: posterior band
BZ: bilaminar (retrodiscal) zone
C: condyle
SLP: sup. part of lat. pterygoid muscle
ILP: inf. part of lat. pterygoid muscle
Bilaminar (retrodiscal) zone is enclosed
by the posterior band of the disc, the
superior and inferior retrodiscal laminae
and the articular capsule. Is highly
vascularised (veinous plexus) and contains
a lot of nerve endings.

7. Capsule, ligaments
Capsule is loose, encloses the mandibular
fossa and the articular tubercle and inserts
around of the neck of mandible.
Lateral and medial (temporomandibular)
ligaments strenghten the joint capsule and
limit anterior and posterior movements.
Sphenomandibular ligament is the
remnant of the Meckel-cartilage. Just like
the stylomandibular ligament has no
real function in the movments of the
TMJ.
Lateral ligament is the strongest and
functionally the most important!

8. Blood supply and innervation of TMJ
• from ext. carotid artery:
• superficial temporal (st)
• from maxillary artery:
• anterior tympanic (at)
• deep auricular (da)
• deep temporal (dt)
Mainly the articular branches of the
auriculotemporal nerve arising from
the mandibular division of trigeminal
nerve, but branches of the facial
nerve contribute to the innervation
of the TMJ in approx. 50% of
individuals.

9. Biomechanics of mastication
 Open-close movement
(synonyms: abduction-adduction or elevation-depression)
 1st phase: rotation in the discomandibular joint around a
bicondylar axis, e.g. during talk;
 2nd phase: gliding in the discotemporal joint around a
transverse axis connecting the two mandibular foramina.
New axis
of rotation

10. At around 15° the lateral ligament stretches and avoids further pure
rotation within the discomandibular joint. Original transverse axis
shifts forward-downward and as a result of movement within the
discotemporal joint the head of the mandible climbs onto the articular
tubercle.
less then 15°
more then 15°

12.  Translation
 Condyles move forward
(protrusion) and backward
(retraction) along a sagittal
line. Movement is primarily
performed within the
discotemporal joints.
Retraction from the neutral position is almost impossible as the head of
mandible is arrested by the external acoustic meatus, and mouth has to
be slightly opened for protrusion otherwise upper front teeth will not
let the lower ones to move forward.

13.  Grinding
 The simpliest definition: rotation of the mandible around an
arbitrary vertical axis perpendicular to the intercondylar line. The
number of such axes is unlimited!
a) Left is the resting, right is the swinging condyle. The left rotates around a vertical axis passing
through it, while the right head moves forward and backward.
b) Right is the resting condyle which performs rotation around a vertical axis, and the left
condyle swings anteriorly-posteriorly.
c) Both the condyles swing: one forward, the other one backward and vice versa. Axis of
rotation is a vertical axis located half way between the two condyles.

14. Muscles of mastication

15. After removing
Temporalis and
Masseter muscles

16. After removing Lateral
Pterygoid muscle

18. Clinical-radiological considerations

20. 1. Disc displacement

21. 2. Bilateral and unilateral (more frequent) dislocation.

23. Muscles of facial expression
All of them are
innervated by the
facial nerve (CN7).

24. Thank you for your attention!