Final answer:
The posterior longitudinal ligament is located in the vertebral canal, preventing posterior protrusion of the intervertebral disk and offering protection to the spinal cord.
Step-by-step explanation:
The posterior longitudinal ligament is within the vertebral canal and prevents posterior protrusion of the intervertebral disk and spinal cords.
The function of the posterior longitudinal ligament is to provide support and prevent hyperflexion, which can cause injury or herniation to the intervertebral disks. It runs along the back (posterior) portion of the vertebral bodies inside the spinal canal, from the second cervical vertebra to the sacrum. This ligament's anatomic position is crucial as it braces the intervertebral disks, limiting their posterior expansion and providing protection to the spinal cord that lies just behind it.