These curves increase the vertebral column’s strength, flexibility, and ability to absorb shock. The adult vertebral column does not form a straight line, but instead has four curvatures along its length (see Figure 1). In a full-grown giraffe, each cervical vertebra is 11 inches tall. This means that there are large variations in the size of cervical vertebrae, ranging from the very small cervical vertebrae of a shrew to the greatly elongated vertebrae in the neck of a giraffe. However, the sacral and coccygeal fusions do not start until age 20 and are not completed until middle age.Īn interesting anatomical fact is that almost all mammals have seven cervical vertebrae, regardless of body size. Similarly, the coccyx, or tailbone, results from the fusion of four small coccygeal vertebrae. The single sacrum, which is also part of the pelvis, is formed by the fusion of five sacral vertebrae. ![]() The lower back contains the L1–L5 lumbar vertebrae. Below these are the 12 thoracic vertebrae, designated T1–T12. Inferiorly, C1 articulates with the C2 vertebra, and so on. Superiorly, the C1 vertebra articulates (forms a joint) with the occipital condyles of the skull. In the neck, there are seven cervical vertebrae, each designated with the letter “C” followed by its number. The vertebral column is subdivided into five regions, with the vertebrae in each area named for that region and numbered in descending order. The vertebral column originally develops as a series of 33 vertebrae, but this number is eventually reduced to 24 vertebrae, plus the sacrum and coccyx. The vertebral column is curved, with two primary curvatures (thoracic and sacrococcygeal curves) and two secondary curvatures (cervical and lumbar curves). The vertebrae are divided into three regions: cervical C1–C7 vertebrae, thoracic T1–T12 vertebrae, and lumbar L1–L5 vertebrae. The adult vertebral column consists of 24 vertebrae, plus the sacrum and coccyx. The facet complex is surrounded by a watertight synovial capsule, much like the small joints in the fingers that allow for smooth movement.Figure 1. Vertebral Column. The pair that faces downward is the inferior articular facet. The pair that faces upward is the superior articular facet. Facet JointsĮach vertebra has a paired joint on its right side and a second paired joint on its left side, allowing a connection with the vertebrae above and below it. In the lower back it not only contains the spinal cord, it also contains the nerve roots of the lower spine. It is made up of the front (anterior) of the vertebral body, the pedicles on the sides of the vertebral body and the lamina in the back. The spinal canal is a bony tunnel surrounding the spinal cord. They may impair exiting nerve roots and cause pain. If present in the cervical spine they occur at the lowest level (C7) and are called a cervical rib. They provide a place for the back muscles to attach to the spine.įor the most part, these are absent in the vertebra of the neck (the cervical spine). The transverse processes are located at right angles to the junction of pedicles and the lamina. Sometimes these processes are absent or bifid in the cervical spine. Each spinous process is attached to the spinous process above and below it by ligaments. They are bony projections that arise at right angles (perpendicular) to the midline of the lamina. The bumps that can be felt down the back are the spinous processes. The lamina is is the roof of the spinal canal that provides support and protection for the backside of the spinal cord. The pedicles also serve as a bridge, joining the front and back parts of the vertebra. PediclesĮach vertebra has two cylinder-shaped projections (pedicles) of hard bone that stick out from the back part of the vertebral body, providing side protection for the spinal cord and nerves. Both the vertebral body and the discs increase in size from the head to the sacrum. The front or anterior section of the vertebral body protects the spinal cord and nerve roots. It bears about 80 percent of the load while standing and provides an attachment for the discs between the vertebrae. The vertebral body is the main portion of the vertebra. Each vertebra is composed of several parts that act as a whole to surround and protect the spinal cord and nerves, provide structure to the body and enable fluid movement in many planes. The adult spine is made up of approximately 24 bones (vertebrae) stacked on top of each other from the bottom of the skull to the pelvis.
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