How many layers does the posterior longitudinal ligament have?

How many layers does the posterior longitudinal ligament have?

• A. Two layers
• B. Three layers
• C. One layer
• D. Four layers

Answer: (B)

The posterior longitudinal ligament is organized as three layers along its course. The outer layer attaches to the posterior aspects of the vertebral bodies and discs and is relatively loose, allowing some flexibility. The middle layer is the thickest and provides most of the resistance to forward bending and to posteriorly displaced disc material. The inner layer lies closest to the dural sac and blends with the dura, helping to stabilize the thecal sac and limit posterior protrusion of disc content. This layered arrangement makes the PLL taut in flexion, protecting neural structures, and explains its continuity with the tectorial membrane higher up in the cranial region.

The posterior longitudinal ligament is organized as three layers along its course. The outer layer attaches to the posterior aspects of the vertebral bodies and discs and is relatively loose, allowing some flexibility. The middle layer is the thickest and provides most of the resistance to forward bending and to posteriorly displaced disc material. The inner layer lies closest to the dural sac and blends with the dura, helping to stabilize the thecal sac and limit posterior protrusion of disc content. This layered arrangement makes the PLL taut in flexion, protecting neural structures, and explains its continuity with the tectorial membrane higher up in the cranial region.