Lumbar Spine

• The lumbar spine consists of 5 vertebrae and 5 lumbar spinal nerve pairs, which exit the spinal canal inferior to their respective vertebrae.

• The lumbar vertebral region displays lordosis (concave posteriorly / curves inward similar to the cervical region).

• Lumbar vertebral bodies are larger than cervical and thoracic vertebral bodies to support the upper body's weight.

• The spinal cord typically terminates between T12 and L2 as the conus medullaris. Lumbar punctures are performed below L2 to avoid the spinal cord.

• Lumbar vertebral foramina are larger than those in the thoracic region but smaller than cervical vertebrae, attributed to the "lumbosacral enlargement," where lower limb spinal nerves exit.

• The sacrum is composed of 5 fused vertebrae and forms the posterior wall of the pelvis.

• The coccyx is composed of 3-5 fused vertebrae and serves as an attachment site for multiple pelvic floor muscles. The filum terminal extends from the conus medullaris to the coccyx, anchoring the spinal cord within the spinal canal.

Clinical correlate:

• Disc herniation is most common in the lumbar spine due to increased weight-bearing forces (see image on the right).