and ears; six are ear bones. With the exception
of the lower jaw bone (mandible) and the ear
bones, all skull bones are joined together and fixed
in one position. The seams where they join are
known as sutures.
Cranial Bones. The cranium is formed by
eight cranial bones, six of which are essential to
know. The FRONTAL BONE, which forms the
forehead, contains the frontal sinuses and helps
form the eye socket and nasal cavity. The two
PARIETAL BONES form the roof of the skull.
The two TEMPORAL BONES, which help form
the sides and base of the skull, also house the
auditory, or 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.
Facial Bones. The two MAXILLARY
BONES form the upper jaw, nasal walls, and part
of the eye socket. These bones contain large
cavities called maxillary sinuses. Frequently these
sinuses become infected, causing the individual
much discomfort. The lower jaw is called the
Figure 3-16.Vertebral column.
Figure 3-17.Vertebra structure.
MANDIBLE. Its main function is mastication.
Other bones of the face are the LACRIMAL and
VERTEBRAL (SPINAL) COLUMN. It
consists of 24 movable or true vertebrae, the
sacrum, and the coccyx, or tail bone (fig. 3-16).
The spinal column is divided into five regions in
the following order: cervical (neck), thoracic
(chest), lumbar (lower back), and sacral and coc-
The vertebrae protect the spinal cord and the
nerves arising from the spinal cord. Each vertebra
has an anterior portion, the body, which is the
large solid segment of the bone (fig. 3-17). This
body is for support, not only for the spinal cord,
but for other structures of the body as well. Many
of the main muscles are attached to the vertebrae.
The vertebral foramen is a hole directly behind
the body of the vertebrae and forms the passage
for the spinal cord. The vertebral projections are
for the attachments of muscles and ligaments and