Figure 3-18.Thorax, anterior view.
to facilitate movement of one vertebra over
the fusion of five false vertebrae. It articulates on
There are seven cervical vertebrae in the neck.
The first is called the ATLAS and resembles a
bony ring. It supports the head. The second is the
highly specialized AXIS. It has a bony prominence
that fits into the ring of the atlas, thus permit-
ting the head to rotate from side to side. The atlas
and the axis are the only named vertebrae, all
others are numbered. Each cervical vertebrae has
a transverse foramen to allow passage of nerves,
the vertebral artery, and a vein. The seventh cer-
vical vertebra has an especially prominent projec-
tion that can easily be felt at the nape of the neck.
This makes it possible for physicians to count and
identify the vertebrae above and below it.
There are 12 vertebrae in the thoracic region.
These articulate with the posterior portion of the
12 ribs to form the posterior wall of the thoracic,
or chest, cage.
There are five lumbar vertebrae, which are the
largest segments of the vertebral column.
The SACRUM is the triangular bone im-
mediately below the lumbar vertebrae, formed by
each side with the hip bone and with the
COCCYX to form the posterior wall of the
THORAX. It is a cone-shaped bony cage,
about as wide as it is deep (fig. 3-18). It is formed
by 12 ribs on each side, which articulate posteri-
orly with the thoracic vertebrae. The first seven
pairs of ribs are attached to the sternum by car-
tilage and are called true ribs. The eighth, ninth,
and tenth ribs are united by their cartilages to the
cartilage of the seventh rib and are called false
ribs. The STERNUM is an elongated flat bone,
forming the middle portion of the upper half of
the chest wall in front. The xiphoid process,
located at the inferior aspect of the sternum,
serves as a landmark in the administration of car-
UPPER EXTREMITY. The upper extremity
consists of the bones of the shoulder, the arm,