Page 268 - Fundamentals of anatomy physiology
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Chapter 7 The Axial Skeleton 255
Clinical Note in the muscles of the abdominal wall. Scoliosis (sko. -le. -O. -sis; 7
scoliosis, crookedness) is an abnormal lateral curvature of the
Kyphosis, Lordosis, and Scoliosis The vertebral column spine in one or more of the movable vertebrae (Photo c). Sco-
must move, balance, and support the trunk and head. Con- liosis is the most common distortion of the spinal curvature.
ditions or events that damage the bones, muscles, and/or This condition may result from developmental problems from
nerves can result in distorted shapes and impaired function. damage to vertebral bodies, or from muscular paralysis affect-
In kyphosis (kı.-FO. -sis; kyphos, humpbacked, bent), the normal ing one side of the back (as in some cases of polio). In 4 out
thoracic curvature becomes exaggerated posteriorly, produc- of 5 cases, the structural or functional cause of the abnormal
ing a “round-back” appearance (Photo a). This condition can spinal curvature is impossible to determine. This idiopathic
be caused by (1) osteoporosis with compression fractures af- (of no known cause) scoliosis generally appears in girls during
fecting the anterior portions of vertebral bodies, (2) chronic adolescence, when periods of growth are most rapid. Small
contractions in muscles that insert on the vertebrae, or (3) curves may later stabilize once growth is complete. For larger
abnormal vertebral growth. In lordosis (lor-DO. -sis; lordosis, curves, bracing may prevent progression. Severe cases can be
a bending backward), or “swayback,” both the abdomen and treated through surgical straightening with implanted metal
buttocks protrude abnormally (Photo b). The cause is an ante- rods or cables.
rior exaggeration of the lumbar curvature. This may occur dur-
ing pregnancy or result from abdominal obesity or weakness
a Kyphosis b Lordosis c Scoliosis
Note that when we refer to a specific vertebra, we use a region. We will see how regional variations determine each
capital letter for the vertebral region: C, T, L, S, and Co rep- vertebral group’s function.
resent the cervical, thoracic, lumbar, sacral, and coccygeal re-
gions, respectively. In addition, we use a numerical subscript Cervical Vertebrae
to indicate the relative position of the vertebra within that
region, with 1 indicating the vertebra closest to the skull. For Most mammals—whether giraffes, whales, mice, or humans—
example, C1 is in contact with the skull and C3 is the third cer- have seven cervical vertebrae (Figure 7–19a). The cervical ver-
vical vertebra. Similarly, T12 is in contact with L1 and L4 is the tebrae are the smallest in the vertebral column. They extend
fourth lumbar vertebra (Figure 7–17). We will use this short- from the occipital bone of the skull to the thorax. The body of
hand throughout the text. a cervical vertebra is small compared with the size of the verte-
bral foramen (Figure 7–19b). At this level, the spinal cord still
Each vertebra has characteristic markings and articula- contains most of the axons that connect the brain to the rest of
tions, but we will focus on the general characteristics of each
