Nerves of the Lumbar Spine

The lumbar spinal nerves lie in the intervertebral foraminae, and are connected by spinal nerve roots to the spinal cord. The spinal nerves divide into the ventral and dorsal rami outside the vertebral column. The lumbar sympathetic trunks run along the anterolateral lumbar vertebral column, and they communicate with the ventral rami of the lumbar spinal nerves

Lumbar Spinal Nerves

• The lumbar spinal nerves are numbered according to the vertebra beneath which they lie. The L1 spinal nerve lies below the L1 vertebra in the L1/2 intervertebral foramen. The L2 spinal nerve lies below the L2 vertebra in the L2/3 intervertebral foramen etc.
• Each spinal nerve is connected centrally to the spinal cord by a dorsal and ventral root.
  • The joining of the spinal nerve roots to the spinal nerve occurs in the intervertebral foramen.
• The spinal nerve divides peripherally into a larger ventral ramus and smaller dorsal ramus.
  • The branching into the two rami occurs outside the foramen.
• The spinal nerves are short, and no longer than the width of their intervertebral foramen.
  • They are generally a few millimetres, but can be less than 1mm with the roots branching directly into rami without the formation of a proper spinal nerve.