Page 270 - Fundamentals of anatomy physiology
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Chapter 7 The Axial Skeleton 257
Table 7–1 Regional Differences in Vertebral Structure and Function
Feature Cervical Vertebrae (7) Type (Number) Lumbar Vertebrae (5)
Thoracic Vertebrae (12) Inferior portion of back
Massive, oval, flat faces
Location Neck Chest
Body Small, oval, curved faces Small
Medium, heart-shaped, flat faces; facets for Blunt, broad; points posteriorly
Vertebral foramen Large rib articulations Short; no articular facets or transverse
Spinous process Long; split tip; points inferiorly Medium foramina
Transverse processes Have transverse foramina Support weight of head, neck, upper
Long, slender; not split; points inferiorly limbs, and trunk
Functions Support skull, stabilize relative positions 7
of brain and spinal cord, and allow All but two (T11, T12) have facets for rib
controlled head movement articulations
Support weight of head, neck, upper limbs,
Typical appearance (superior view) and chest; articulate with ribs to allow
changes in volume of thoracic cage
Table 7–1 includes a summary of the features of these cervical vertebra is named after Atlas, who, according to Greek myth,
vertebrae. holds the world on his shoulders. The articulation between the
occipital condyles and the atlas is a joint that permits you to
Compared with the cervical vertebrae, your head is rela- nod (such as when you indicate “yes”). The atlas can easily be
tively massive. It sits atop the cervical vertebrae like a soup distinguished from other vertebrae by (1) the lack of a body
bowl on the tip of a finger. With this arrangement, small mus- and spinous process and (2) the presence of a large, round ver-
cles can produce significant effects by tipping the balance one tebral foramen bounded by anterior and posterior arches.
way or another. But if you change position suddenly, as in a
fall or during rapid acceleration (a jet takeoff) or deceleration The atlas articulates with the second cervical vertebra, the
(a car crash), the balancing muscles are not strong enough to axis. This articulation permits rotation (as when you shake
stabilize the head. A dangerous partial or complete dislocation your head to indicate “no”).
of the cervical vertebrae can result, with injury to muscles and
ligaments and potential injury to the spinal cord. We use the The Axis (C2)
term whiplash to describe such an injury, because the move-
ment of the head resembles the cracking of a whip. During development, the body of the atlas fuses to the body of
the second cervical vertebra, called the axis (C2) (Figure 7–19d).
The Atlas (C1) This fusion creates the prominent dens (DENZ; dens, tooth),
or odontoid (o. -DON-toyd; odontos, tooth) process, of the axis.
The atlas, cervical vertebra C1 (Figure 7–19d), holds up the A transverse ligament binds the dens to the inner surface of
head. It articulates with the occipital condyles of the skull. This the atlas, forming a pivot for rotation of the atlas and skull.
