Intervertebral joints contain intervertebral discs and ligaments that allow for vertebral movements PDF

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Intervertebral joints contain intervertebral discs and ligaments that allow for vertebral movements...

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Intervertebral joints contain intervertebral discs and ligaments that allow for vertebral movements The articulations between adjacent vertebrae form two types of joints—symphyses and synovial—that permit small movements associated with flexion and rotation of the vertebral column (Figure 9–6a). Little movement occurs between adjacent vertebral bodies. From axis to sacrum, the vertebrae are separated and cushioned by pads of fibrocartilage called intervertebral discs. Thus, the bodies of vertebrae form symphyses. Intervertebral discs and symphyses are not found between the first and second cervical vertebrae or in the sacrum or coccyx, where vertebrae have fused. Recall that the first cervical vertebra has no vertebral body and no intervertebral disc. The only joint between the first two cervical vertebrae is a synovial joint that allows much more rotation than the symphyses between other cervical vertebrae Structure of Intervertebral Joints Intervertebral joints are joints between adjacent vertebral bodies (these are symphyses) and joints between adjacent articular processes (these are synovial) along the vertebral column. Let's look at the structure of the intervertebral discs and ligaments that support these joints. Intervertebral Discs Each intervertebral disc has a tough outer layer of fibrocartilage, the anulus fibrosus (AN-u . -lus fı . -BRO . -sus). The collagen fibers of this layer attach the disc to the bodies of adjacent vertebrae. The anulus fibrosus surrounds the nucleus pulposus (pul-PO . -sus), a soft, elastic, gelatinous core. The nucleus pulposus gives the disc resiliency and enables it to absorb shocks. The superior and inferior surfaces of the disc are almost completely covered by thin vertebral end plates that are composed of hyaline cartilage and fibrocartilage (Figure 9–6b). Movement of the vertebral column compresses the nucleus pulposus and displaces it in the opposite direction. This displacement permits smooth gliding movements

between vertebrae while maintaining their alignment. The intervertebral discs make a significant contribution to a person’s height: They account for about one-quarter of the length of the vertebral column superior to the sacrum. As we grow older, the water content of the nucleus pulposus in each disc decreases. The discs gradually become less effective as cushions, and the chances of vertebral injury increase. Water loss from the discs also causes the vertebral column to shorten, accounting for the characteristic decrease in height as we get older. Intervertebral Ligaments Numerous strong ligaments are attached to the bodies and processes of all vertebrae, binding them together and stabilizing the vertebral column (see Figure 9–6b). Ligaments interconnecting adjacent vertebrae include the following: ■ The ligamenta flava are paired ligaments that connect the laminae of adjacent vertebrae. ■ The posterior longitudinal ligament is a fibrous band that parallels the anterior longitudinal ligament and connects the posterior surfaces of adjacent vertebral bodies....