Check Your Understanding
What are the three main parts of the axial skeleton?
Which part of the skeleton—axial or appendicular—is
important in protecting internal organs?
For answers, see Appendix H.
Name, describe, and identify the skull bones. Identify their
Compare and contrast the major functions of the cranium
and the facial skeleton.
is the body’s most complex bony structure. It is
, 22 in all. Te cranial bones,
ne-um), enclose and protect the fragile brain
and furnish attachment sites for head and neck muscles. Te
facial bones (1) form the framework of the face, (2) contain
cavities for the special sense organs of sight, taste, and smell,
(3) provide openings for air and food passage, (4) secure the
teeth, and (5) anchor the facial muscles of expression, which
we use to show our feelings. As you will see, the individual skull
bones are well suited to their assignments.
Most skull bones are ﬂat bones. Except for the mandible,
which is connected to the rest of the skull by freely movable
joints, all bones of the adult skull are ﬁrmly united by interlock-
ing joints called
cherz). Te suture lines have a
saw-toothed or serrated appearance.
Te major skull sutures, the
, connect cranial bones (Figures 7.2a, 7.4b, and
7.5a). Most other skull sutures connect facial bones and are
named according to the speciﬁc bones they connect.
Overview of Skull Geography
It is worth surveying basic skull “geography” before describing
the individual bones. With the lower jaw removed, the skull re-
sembles a lopsided, hollow, bony sphere. Te facial bones form
its anterior aspect, and the cranium forms the rest of the skull
Te cranium can be divided into a vault and a base. Te
, also called the
re-ah; “bald part of
skull”), forms the superior, lateral, and posterior aspects of the
skull, as well as the forehead. Te
forms the skull’s
inferior aspect. Internally, prominent bony ridges divide the
base into three distinct “steps” or fossae—the
posterior cranial fossae
(Figure 7.2b and c). Te brain sits
snugly in these cranial fossae, completely enclosed by the cra-
nial vault. Overall, the brain is said to occupy the
In addition to the large cranial cavity, the skull has many
smaller cavities. Tese include the middle and internal ear cavi-
ties (carved into the lateral side of its base) and, anteriorly, the
Bones of cranium
(a) Cranial and facial divisions of the skull
(b) Superior view of the cranial fossae
(c) Lateral view of cranial fossae showing the contained
Cranial and facial divisions and fossae.