The series of vertebrae that protect the spinal cord; the spinal column.
is an exaggerated concave (kyphotic)
curvature of the thoracic vertebral column; it is commonly known as "humpback."
Lordosis is an exaggerated convex (lordotic) curvature of the lumbar region; it is commonly known as "swayback."
Scoliosis is an abnormal lateral curvature of the vertebral column.
Number of Vertebrae
In human anatomy, the vertebral column (backbone or spine) usually consists of 24 articulating vertebrae and nine fused vertebrae in the sacrum and the coccyx. Situated in the dorsal aspect of the torso and separated by intervertebral discs, it houses and protects the spinal cord in its spinal canal. There are normally 33 vertebrae in humans, including the five that are fused to form the sacrum, the four coccygeal bones that form the tailbone, and the others separated by intervertebral discs. The upper three regions comprise the remaining 24, and are grouped as cervical (seven vertebrae), thoracic (12 vertebrae) and lumbar (five vertebrae).
A typical vertebra consists of the vertebral
body and vertebral arch. These parts together enclose the vertebral
foramen that contains the spinal
cord. The vertebral arch is formed by a pair of pedicles and a pair of laminae. Two transverse processes and one spinous
process are posterior to (behind) the vertebral body. The spinous process projects
toward the posterior direction, while one transverse process projects to the left
and the other to the right. The spinous processes of the cervical and lumbar
regions can be felt through the skin. Facet joints are located above and below
each vertebra. These restrict the range of movement. Between each
pair of vertebrae are two small openings called intervertebral foramina through which the spinal
When viewed laterally, the vertebral column presents several curves corresponding to the different regions of the column: cervical, thoracic, lumbar, and pelvic.
Cervical and Thoracic Curves
The cervical curve convexes forward and begins at the apex
of the odontoid (tooth-like) process. It ends at the middle of the
second thoracic vertebra. The thoracic curve convexes dorsally,
begins at the middle of the second thoracic vertebra, and ends at the middle of
the 12th thoracic vertebra.
The lumbar curve, which is more pronounced in women than in men, begins at
the middle of the last thoracic vertebra and ends at the sacrovertebral angle.
It is convex anteriorly with the lower three vertebrae much more convex than the upper two. This curve is described as a lordotic
curve. The pelvic curve begins at the sacrovertebral articulation and ends at the point of the
coccyx; its concavity is directed downward and forward.
Primary and Secondary Curves
The thoracic and sacral curvatures are termed primary curves because they are present in the fetus and remain the same in the adult. As the child grows,
lifts the head, and begins to assume an upright position, the secondary curves
(cervical and lumbar) develop. The cervical curve forms when the infant is able
to hold up his or her head (at three or four months) and sit upright (at nine
months). The lumbar curve forms between twelve to eighteen months when the
child begins to walk.