212
UNIT 2
Covering, Support, and Movement of the Body
7
Lacrimal Bones
Te delicate, fingernail-shaped
lacrimal bones
(lak
9
rĭ-mal)
contribute to the medial walls of each orbit (Figures 7.4a and
7.5a). Tey articulate with the frontal bone superiorly, the eth-
moid bone posteriorly, and the maxillae anteriorly. Each lac-
rimal bone contains a deep groove that helps form a
lacrimal
fossa
. Te lacrimal fossa houses the
lacrimal sac
, part of the
passageway that allows tears to drain from the eye surface into
the nasal cavity (
lacrima
5
tears).
Palatine Bones
Each L-shaped
palatine bone
is fashioned from two bony
plates, the
horizontal
and
perpendicular
(see Figures 7.13a and
7.6a), and has three important articular processes, the
pyrami-
dal
,
sphenoidal
, and
orbital
. Te
horizontal plates
, joined at the
median palatine suture, complete the posterior portion of the
hard palate. Te superiorly projecting
perpendicular (vertical)
plates
form part of the posterolateral walls of the nasal cavity
and a small part of the orbits.
Vomer
Te slender, plow-shaped
vomer
(vo
9
mer; “plow”) lies in the
nasal cavity, where it forms part of the nasal septum (see Fig-
ures 7.4a and 7.13b). It is described below in connection with
the nasal cavity.
Inferior Nasal Conchae
Te paired
inferior nasal conchae
are thin, curved bones in
the nasal cavity. Tey project medially from the lateral walls
of the nasal cavity, just inferior to the middle nasal conchae of
the ethmoid bone (see Figures 7.4a and 7.13a). Tey are the
largest of the three pairs of conchae and, like the others, they
form part of the lateral walls of the nasal cavity.
Check Your Understanding
7.
Women with prominent (high) cheekbones are often
considered beautiful by the modeling industry. What bones
are the “cheekbones”?
8.
Johnny was vigorously exercising the only joints in the skull
that are freely movable. What would you guess he was
doing?
9.
What bones are the keystone bones of the facial skeleton?
For answers, see Appendix H.
Special Characteristics of the Orbits
and Nasal Cavity
Define the bony boundaries of the orbits, nasal cavity, and
paranasal sinuses.
±wo restricted skull regions, the orbits and the nasal cavity, are
formed from an amazing number of bones. Even though we have
already described the individual bones forming these structures,
we give a brief summary here to pull the parts together.
to pass to the teeth in the lower jaw. Dentists inject lidocaine
into these foramina to prevent pain while working on the lower
teeth. Te
mental foramina
, openings on the lateral aspects of
the mandibular body, allow blood vessels and nerves to pass to
the skin of the chin (
ment
5
chin) and lower lip.
Maxillary Bones
Te
maxillary bones
, or
maxillae
(mak-sil
9
le; “jaws”) (Fig-
ures 7.4 to 7.6 and 7.11b and c), are fused medially. Tey form
the upper jaw and the central portion of the facial skeleton.
All facial bones except the mandible articulate with the max-
illae. Hence, the maxillae are considered the keystone bones
of the facial skeleton.
Te maxillae carry the upper teeth in their
alveolar pro-
cesses
. Just inferior to the nose the maxillae meet medially,
forming the pointed
anterior nasal spine
at their junction. Te
palatine processes
(pa˘
9
lah-tīn) of the maxillae project posteri-
orly from the alveolar processes and fuse medially at the
inter-
maxillary suture
, forming the anterior two-thirds of the hard
palate, or bony roof of the mouth (Figures 7.5c and d and 7.6).
Just posterior to the teeth is a midline foramen, called the
inci-
sive fossa
, which serves as a passageway for blood vessels and
nerves.
Te
frontal processes
extend superiorly to the frontal bone,
forming part of the lateral aspects of the bridge of the nose
(Figures 7.4a and 7.11b). Te regions that flank the nasal cavity
laterally contain the
maxillary sinuses
(see Figure 7.14), the
largest of the paranasal sinuses. Tey extend from the orbits to
the roots of the upper teeth. Laterally, the maxillae articulate
with the zygomatic bones via their
zygomatic processes
.
Te
inferior orbital fissure
is located deep within the orbit
(Figure 7.4a) at the junction of the maxilla with the greater wing
of the sphenoid. It permits the zygomatic nerve, the maxillary
nerve (a branch of cranial nerve V), and blood vessels to pass to
the face. Just below the eye socket on each side is an
infraorbital
foramen
that allows the infraorbital nerve (a continuation of
the maxillary nerve) and artery to reach the face.
Zygomatic Bones
Te irregularly shaped
zygomatic bones
(Figures 7.4a, 7.5a,
and 7.6) are commonly called the cheekbones (
zygoma
5
cheekbone). Tey articulate with the zygomatic processes
of the temporal bones posteriorly, the zygomatic processes
of the frontal bone superiorly, and with the zygomatic pro-
cesses of the maxillae anteriorly. Te zygomatic bones form
the prominences of the cheeks and part of the inferolateral
margins of the orbits.
Nasal Bones
Te thin, basically rectangular
nasal bones
(na
9
zal) are fused
medially, forming the bridge of the nose (Figures 7.4a and 7.5a).
Tey articulate with the frontal bone superiorly, the maxillary
bones laterally, and the perpendicular plate of the ethmoid bone
posteriorly. Inferiorly they attach to the cartilages that form
most of the skeleton of the external nose.
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