The Head Is Formed by the Skull
and Hyoid Bones
The skull, which consists of 22 bones, rests on top of the
vertebral column. It has two groups of bones: 8 cranial
bones and 14 facial bones. The cranial bones protect the
brain and form attachment points
for the meninges (
me-NIN-jez
) on
the interior and the muscles that
move the head on the exterior.
The facial bones house the open-
ings to the airways and the digestive system, protect the
sensory organs (eyes, ears, nose, and taste buds), and pro-
vide attachments for facial muscles.
Cranial b o n e s The cranium consists of the following
bones (Figure 5.8, on the next page):
The frontal bone forms the forehead, roofs of the eye
sockets, and front part of the cranial floor. The mucous
membrane-lined spaces (frontal sinuses) deep within
it resonate sound.
The parietal (
pa-Rl-e-tal
) bones (2) form the sides
and roof of the cranium
The temporal bones (2) form the lower side of the
cranium and part of the cranial floor. The temporal
bones have several features:
• They form joints with the jawbone (mandible) called
the temporomandibular joints (TMJ).
• The external auditory meatus is the canal that
leads to the middle ear.
• The mastoid process is a point of attachment for
some of the muscles involved in head movement.
• The carotid artery passes through
a foramen called the carotid
foramen.
• The styloid process serves as
a point of attachment for the
tongue and neck muscles.
The occipital bone (
ok-SIP-i-tal
) forms the back part
of the skull and most of the cranial floor. The medulla,
spinal cord, and vertebral and spinal arteries all pass
through its foramen magnum. The first
cervical
vertebra attaches to the occipital bone at two processes
called the occipital condyles.
The sphenoid bone (
SFE-noyd
) is in the middle of the
cranial floor and is where all the other cranial bones
attach, like the keystone joining two arches to form
a doorway. It contains sphenoidal sinuses, which
drain into the nasal cavity. The pituitary gland sits
in a depression of the sphenoid bone called the sella
turcica. The optic nerve passes through its optic
foramen, and the mandibular nerve passes through
its foramen ovale.
The ethmoid bone (ETH-moid) forms the anterior
part of the cranial floor, the medial part of the eye
sockets, and superior portions of the nasal cavity. It has
3 to 18 ethmoidal sinuses (air spaces) and mucus-
lined conchae that warm and moisten inhaled air
and trap foreign particles. The crista galli, a ridge on
the superior portion of the ethmoid bone, serves as an
attachment point for the meninges. This is surrounded
by the cribriform plate through which the nerves
associated with the receptors for smell pass from the
nose into the brain.
Facial
b o n e s Your face changes and grows from
the time you are born until around age 16. Your teeth
form and erupt, the cranial bones grow, and the pa-
ranasal sinuses expand. Your facial bones include the
following:
Nasal bones (2) form the bridge of the nose.
Maxillae (
mak-SIL-e
; singular is
maxilla)
(2) form the
upper jawbone and join with all the other facial bones
except the mandible (lower jawbone):
• Each maxilla has a maxillary sinus that empties
into the nasal cavity.
• The alveolar process
(
al-VE-o-lar
)
forms
the
arch that contains the sockets (alveoli) for the
teeth.
• The maxillae form the anterior three-fourths of the
roof of the mouth (hard palate).
Palatine bones (
PAL-a-tin
) (2) form the posterior
portion of the hard palate, part of the lower eye
sockets, and part of the floor and the sides of the
nasal cavity.
The mandible is the largest, strongest facial bone and
the only one that moves:
• Each condylar process
(
KON-di-lar
)
forms a
temporomandibular joint
with
each
temporal
bone.
• Like the maxillae, the mandible has an alveolar
process for the lower teeth.
meninges
(me-NIN-
jez) Three membranes
that cover the brain
and spinal cord.
foramen
(fo-RA-men)
A hole in a bone for
passage of vessels
or nerves (plural is
foramina).
The Axial Skeleton is Composed of 80 Bones 123
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