SKULL.The skull consists of 28 bones (figs.
1-15 and 1-16), 22 of which form the framework of the
head and provide protection for the brain, eyes, and
ears; six are ear bones. With the exception of the lower
jaw bone and the ear bones, all skull bones are joined
together and fixed in one position. The seams where
they join are known as sutures. The bones of the skull
are classified as either cranial or facial bones.
Cranial Bones.The cranium is formed by eight
major bones, most of which are in pairs (fig. 1-15). The
frontal bone forms the forehead and the roof of each
orbit (or eye socket) and the nasal cavity. The parietal
bones form the roof of the skull. The temporal bones
help form the sides and base of the skull and also house
the auditory and hearing organs. The occipital bone
forms part of the base and back of the skull, and
contains a large hole called the foramen magnum. This
opening permits passage of the spinal cord from the
cranium into the spinal column. The sphenoid bones
are wedged between several other bones in the anterior
portion of the skull. These bones help form the base of
the cranium, the sides of the skull, and the floors and
sides of the orbits. The ethmoid bones are located in
front of the sphenoid bone. They form sections of the
nasal cavity roof, the cranial floor, and the orbital wall.
Facial Bones.The facial bones of the skull
consists of 14 bones: 13 immovable bones and a
movable lower jawbone (fig. 1-16). The facial bones
give the face its basic shape and provide attachment
sites for various muscles that move the jaw and control
BY RED MARROW
Figure 1-14.Anatomy of a long bone.
Figure 1-15.Lateral view of the skull.