268
UNIT 2
Covering, Support, and Movement of the Body
8
wide. Tis anterior movement braces the condylar process against
the articular tubercle, so that the mandible is not forced through
the thin roof of the mandibular fossa when one bites hard foods
such as nuts or hard candies. Te superior compartment also al-
lows this joint to glide from side to side. As the posterior teeth are
drawn into occlusion during grinding, the mandible moves with
±wo distinct kinds of movement occur at the ±MJ (Figure
8.13c). First, the concave inferior disc surface receives the condylar
process of the mandible and allows the familiar hingelike move-
ment of depressing and elevating the mandible while opening and
closing the mouth. Second, the superior disc surface glides ante-
riorly along with the condylar process when the mouth is opened
Zygomatic process
Mandibular fossa
Articular tubercle
Infratemporal fossa
External
acoustic
meatus
Articular
capsule
Ramus of
mandible
Articular
capsule
Mandibular
fossa
Articular disc
Articular
tubercle
Superior
joint
cavity
Inferior joint
cavity
Condylar
process of
mandible
Ramus of
mandible
Synovial
membranes
(b) Enlargement of a sagittal section through the joint
(a) Location of the joint in the skull
Lateral
ligament
(c)
Lateral excursion: lateral (side-to-side) movements of the mandible
Outline of the
mandibular
fossa
Superior view
Figure 8.13
The temporomandibular
(jaw) joint.
In
(b)
, note that the two
parts of the joint cavity allow different
movements, indicated by arrows. The inferior
compartment of the joint cavity allows the
condylar process of the mandible to rotate in
opening and closing the mouth. The superior
compartment lets the condylar process move
forward to brace against the articular tubercle
when the mouth opens wide, and also allows
lateral excursion of this joint
(c)
.
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