Final answer:
The question pertains to the changes in intervertebral discs and the role of posterior ligaments during movements of the spine. A herniated disc can occur if the anulus fibrosus is weakened, leading to compression of spinal nerves. The posterior longitudinal ligament and the ligamentum flavum provide support to prevent such injuries.
Step-by-step explanation:
When the vertebrae of the spinal column are subjected to movements such as bending forward, the intervertebral discs get compressed, particularly on their anterior side. Meanwhile, the posterior side of these discs expands. The nucleus pulposus, with its gel-like consistency, allows the intervertebral disc to alter its shape in response to these movements. Nevertheless, if the anulus fibrosus is compromised due to injury or age, this could result in the nucleus pulposus herniating or protruding through the anulus fibrosus, leading to a herniated disc.
This herniation often compresses a spinal nerve, causing symptoms like pain and muscle weakness, which could be indicative of sciatica if it occurs at the L4/L5 or L5/S1 intervertebral discs. Furthermore, the posterior longitudinal ligament and the ligamentum flavum are important supportive structures located within the vertebral canal, which become taut during forward flexion, providing crucial support and maintaining spinal stability.