Intervertebral Discs

An intervertebral disc is a pad consisting of an inner gelatinous nucleus pulposus surrounded by a ring of fibrocar-tilage, the annulus fibrosus (see fig. 8.22). The discs help to bind adjacent vertebrae together, support the weight of the body, and absorb shock. Under stress—for example, when you lift a heavy weight—the discs bulge laterally.

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

Chapter 8 The Skeletal System 265

Transverse-

process

Intervertebral disc Inferior articular — process of L3

Superior articular process of L4 Lamina

Transverse-

process

Intervertebral disc Inferior articular — process of L3

Superior articular process of L4 Lamina

Inferior Articular Process

Figure 8.23 Articulated Vertebrae. (a) Dorsal view of vertebrae L3 to L4. (b) Left lateral view of vertebrae L1 to L3.

Superior Vertebral Notch

V notch of L1

Superior vertebral notch of L2

Spinous process

J|— Intervertebral disc

-Superior articular process of L1

-Inferior vertebral

V notch of L1

Superior vertebral notch of L2

Spinous process

Intervertebral foramen

J|— Intervertebral disc

- Inferior articular process of L3

Figure 8.23 Articulated Vertebrae. (a) Dorsal view of vertebrae L3 to L4. (b) Left lateral view of vertebrae L1 to L3.

Excessive stress can crack the annulus and cause the nucleus to ooze out. This is called a herniated disc ("ruptured" or "slipped" disc in lay terms) and may put painful pressure on the spinal cord or a spinal nerve. To relieve the pressure, a procedure called a laminectomy may be performed—each lamina is cut and the laminae and spin-ous processes are removed. This procedure is also used to expose the spinal cord for anatomical study or surgery.

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