A representative vertebra and intervertebral disc are shown in figure 8.22. The most obvious feature of a vertebra is the body, or centrum—a mass of spongy bone and red bone marrow covered with a thin layer of compact bone. This is the weight-bearing portion of the vertebra. Its rough superior and inferior surfaces provide firm attachment to the intervertebral discs.
_Think About It_
The vertebral bodies and intervertebral discs get progressively larger as we look lower and lower on the vertebral column. What is the functional significance of this trend?
Dorsal to the body of each vertebra is a triangular canal called the vertebral foramen. The vertebral foramina collectively form the vertebral canal, a passage for the spinal cord. The foramen is bordered by a bony vertebral arch composed of two parts on each side: a pillarlike pedicle34 and platelike lamina.35 Extending from the apex of the arch, a projection called the spinous process is directed toward
35lamina = layer, plate the rear and downward. You can see and feel the spinous processes as a row of bumps along the spine. A transverse process extends laterally from the point where the pedicle and lamina meet. The spinous and transverse processes provide points of attachment for the spinal muscles.
A pair of superior articular processes project upward from one vertebra and meet a similar pair of inferior articular processes that project downward from the vertebra just above (fig. 8.23a). Each process has a flat articular surface (facet) facing that of the adjacent vertebra. These processes restrict twisting of the vertebral column, which could otherwise severely damage the spinal cord.
When two vertebrae are joined, they exhibit an opening between their pedicles called the intervertebral foramen. This allows passage for spinal nerves that connect with the spinal cord at regular intervals. Each foramen is formed by an inferior vertebral notch in the pedicle of the superior vertebra and a superior vertebral notch in the pedicle of the one just below it (fig. 8.23fc).
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.