Between superior and inferior articular processes of adjacent vertebrae in the spine are found intervertebral joints (articulations).
Intervertebral
Joints
Between superior and inferior
articular processes of adjacent vertebrae in the spine are found intervertebral joints (articulations). These are glid-ing joints, allowing small movements such
as flexion and rotation of the spinal column. However, only slight gliding
occurs between adjacent vertebrae. Therefore, the vertebrae are separated and
cushioned by intervertebral discs,
which are pads of fibrocartilage (FIGURE 8-9). The bodies of the vertebrae form sym-physeal joints.
These joints are present between the axis and sacrum of the spine, but are not
present in the sacrum or coccyx. In these
locations, the vertebrae are fused. Also, the joints between the first and
second cervical vertebrae are fused. Actually, the first cervical vertebra does
not have a vertebral body or an inter-vertebral disc. Therefore, between the
first two cer-vical vertebrae, there is a pivot joint that allows for a greater
amount of rotation than the symphyseal joints between other vertebrae.
Throughout most of the spine,
each intervertebral disc has a tough outer layer of fibrocartilage known as the
annulus fibrosus. Collagen fibers
attach this fibro-cartilage to the bodies of adjacent vertebrae. Inside the
annulus fibrosis is the nucleus
pulposus, a core that is softer,
gelatinous, and more elastic. Intervertebral discs absorb shocks and have
resiliency because of each nucleus pulposus. Thin vertebral end plates nearly cover the superior and inferior
surfaces of each disc. The plates are made up of fibrocartilage and hya-line
cartilage. When movement occurs, the vertebral column compresses the nucleus
pulposus, displacing it in opposing directions. Gliding movements can occur
while vertebral alignment remains constant.
Intervertebral discs make up
nearly one-fourth of the length of the vertebral column superior to the sacrum,
greatly contributing to an individual’s height. However, aging causes water
content of each nucleus pulposus to decrease, reducing their cushioning
actions. This raises the chance of vertebral injury. The water loss results in
vertebral column shortening, and the older individual actually becomes shorter
over time.
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