What is the outer portion of the intervertebral disc called?

• A. Spinal canal
• B. Vertebral body
• C. Annulus fibrosus
• D. Nucleus pulposus

Answer: (C)

The outer portion of an intervertebral disc is the annulus fibrosus. The disc has two main parts: an outer tough ring made of concentric lamellae of collagen—the annulus fibrosus—and a central gel-like core—the nucleus pulposus. The annulus fibrosus encases and contains the nucleus pulposus, providing strength and resistance to twisting and compression by its layered structure. The nucleus pulposus acts as a shock absorber, helping the disc deform under load. The spinal canal is the passageway for the spinal cord, and the vertebral body is the front, weight-bearing part of a vertebra, not part of the disc.