216
UNIT TWO
TABLE
7.6
|
Bones of the Facial Skeleton
Name and Number
Description
Special Features
Maxillary (2)
Form upper jaw, anterior roof of mouth, ±
oors of orbits,
and sides and ±
oor of nasal cavity
Alveolar processes, maxillary sinuses, palatine process
Palatine (2)
Form posterior roof of mouth and ±
oor and lateral walls
of nasal cavity
Zygomatic (2)
Form prominences of cheeks and lateral walls and ±
oors
of orbits
Temporal process
Lacrimal (2)
Form part of medial walls of orbits
Groove that leads from orbit to nasal cavity
Nasal (2)
Form bridge of nose
Vomer (1)
Forms inferior portion of nasal septum
Inferior nasal conchae (2)
Extend into nasal cavity from its lateral walls
Mandible (1)
Forms lower jaw
Body, ramus, mandibular condyle, coronoid process, alveolar process,
mandibular foramen, mental foramen
bones grow together. The posterior fontanel usually closes
about two months after birth; the sphenoidal fontanel closes
at about three months; the mastoid fontanel closes near the
end of the F
rst year; and the anterior fontanel may not close
until the middle or end of the second year.
Other characteristics of an infantile skull
(fig. 7.31)
include a small face with a prominent forehead and large
orbits. The jaw and nasal cavity are small, the sinuses are
incompletely formed, and the frontal bone is in two parts
(reference plate 51). The skull bones are thin, but they are
also somewhat flexible and thus are less easily fractured
than adult bones.
mandible through the
mental foramen,
which opens on
the outside near the point of the jaw. They supply the
tissues of the chin and lower lip.
Table 7.6
describes the fourteen facial bones.
Figure
7.30
shows features of these bones on radiographs.
Table
7.7
lists the major openings
(foramina)
and passageways
through bones of the skull, as well as their general locations
and the structures that pass through them.
Infantile Skull
At birth, the skull is incompletely developed, with F brous
membranes connecting the cranial bones. These membra-
nous areas are called
fontanels
(fon
tah-nel
z), or, more
commonly, soft spots. They permit some movement between
the bones so that the developing skull is partially compress-
ible and can slightly change shape. This action, called
mold-
ing,
enables an infant’s skull to more easily pass through
the birth canal. Eventually, the fontanels close as the cranial
Coronoid
process
Mandibular
foramen
Mandibular condyle
Ramus
Alveolar
border
Mental foramen
Body
Body
Alveolar
arch
Mandibular
foramen
Coronoid process
(a)
(b)
FIGURE 7.29
²Mandible.²(
a
) Left lateral view. (
b
) Inferior view.
In the infantile skull, a frontal suture (metopic suture) separates the
two parts of the developing frontal bone in the midline. This suture
usually closes before the sixth year; however, in a few adults, the fron-
tal suture remains open.
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