Each of these bones can be explored further, using the related
images in the Atlas. Foramina and fissures are present for the
passage of vessels and nerves. The vessels are detailed in
Chapter 21; the nerves are shown in the Focus box on cranial
nerves in Chapter 14.

Cranial Bones

The Occipital Bone (Figure 7–5a)

General Functions:

The occipital bone forms much of the

posterior and inferior surfaces of the cranium.

Articulations:

The occipital bone articulates with the parietal

bones, the temporal bones, the sphenoid, and the first cervical
vertebra (the atlas) (Figures 7–3a–c,e and Figure 7–4).

Regions/Landmarks:

The external occipital protuberance

is a small bump at the midline on the inferior surface.

The external occipital crest, which begins at the external

occipital protuberance, marks the attachment of a ligament
that helps stabilize the vertebrae of the neck.

The occipital condyles are the site of articulation between

the skull and the first vertebra of the neck.

The inferior and superior nuchal (NOO-kul) lines are ridges

that intersect the occipital crest. They mark the attachment
sites of muscles and ligaments that stabilize the articulation at
the occipital condyles and balance the weight of the head over
the vertebrae of the neck.

The concave internal surface of the occipital bone

(

Figure 7–4a

) closely follows the contours of the brain. The

grooves follow the paths of major blood vessels, and the ridges
mark the attachment sites of membranes that stabilize the
position of the brain.

Foramina:

The foramen magnum (

Figure 7–4b

) connects

the cranial cavity with the spinal cavity, which is enclosed by
the vertebral column. This foramen surrounds the connection
between the brain and spinal cord.

The jugular foramen lies between the occipital bone and

the temporal bone (

Figure 7–3e

). The internal jugular vein

passes through this foramen, carrying venous blood from the
brain.

The hypoglossal canals (

Figure 7–4b

) begin at the lateral

base of each occipital condyle and end on the inner surface of
the occipital bone near the foramen magnum. The hypoglossal
nerves, cranial nerves that control the tongue muscles, pass
through these canals.

In this section, we classify cranial nerves as primarily sensory,

special sensory, motor, or mixed (sensory and motor). In this
classification, sensory nerves carry somatic sensory information,
including touch, pressure, vibration, temperature, or pain.

Inferior

nuchal line

External

occipital

protuberance

Foramen
magnum

Superior

nuchal

line

Occipital

condyle

External

occipital
crest

(a) Occipital bone, inferior view

(b) Right parietal bone, lateral view

Superior

temporal line

Inferior

temporal line

Hypoglossal

canal

Figure 7–5

The Occipital and Parietal Bones

166

FOC_FIRST

FOC_H1

FOC_H2

FOC_UL_FIRST

FOC_UL_MID

FOC_UL_MID_LP

FOC_UL_LAST

FOC_UL_LAST_LP

FOC_SUPTTL

FOC_UL_ITEM_TTL

FOC_KT

Focus

The Individual Bones of the Skull

FOC_TTL