Lumbar Spine Anatomy 101


In this post, we’ll cover the basics of lumbar spine anatomy. The lumbar spine is in the lower back (whereas the cervical spine anatomy refers to the neck region).

This curved part of the spine helps support and move the body, and is made up of interlocking bones called vertebrae, ligaments and nerves.

The lumbar spine contains:

  • 5 vertebrae: L1-L5 (referring to each of the lumbar vertebrae)
  • 5 intervertebral discs (a kind of cushion situated between each vertebrae)
  • 5 pairs of exiting nerve roots

A typical lumbar vertebra, such as the L2 vertebra, is made up of the following parts:

  • Body
  • Vertebral foramen/canal
  • Intervertebral foramen
  • Pedicle
  • Transverse process
  • Lamina
  • Spinous process
  • Facet joints
  • Pars interarticularis

Lumbar fusion surgery is an operation to fuse vertebrae in the lower back.

Sacral anatomy

Lumbar lordosis refers to the curvature of the spine. The apex — or most curved point — of lumbar lordosis falls at about vertebra L3 or L4. The lumbar lordosis of vertebrae L1 through S1 ranges from 30 degrees to 80 degrees, with S1 being the first sacral vertebra.

The sacrum is a series of three, four or five fused coccygeal vertebrae at the base of the spine. The coccyx (or tailbone) articulates — or forms a joint — with the inferior aspect of the sacrum.

Ligaments and nerve structures

There are ligaments throughout the lumbar spine. Inside the lumbar spine, you’ll find the following ligaments:

  • Anterior longitudinal ligament
  • Posterior longitudinal ligament
  • Ligamentum flavum
  • Interspinous ligaments
  • Supraspinous ligament
  • Intertransverse ligaments

The spinal cord and nerve roots are often affected by skeletal problems. Discs and bony tissue can interfere with normal nerve function and cause pain.

Conus medularis: The point at which the thick, single strand of the spinal cord ends — typically at T12 (referring to a thoracic vertebra) or L1

Cauda equina: The point at which individual nerve roots continue down through the spinal canal

The exiting nerve roots passes medial (middle) to the pedicle of the anatomic segment. The traversing nerve roots pass across the disc space and beneath the pedicles of the inferior segment below.

Vascular structures

The aorta and vena cava bifurcate — or divide into two branches — around the level of the L3 or L4 disc space. Vascular structures in the lumbar spine include:

  • Aorta
  • Vena cava
  • Iliac arteries
  • Iliac veins
  • Midsacral vessels

If you have questions about pain in your lumbar spine, consult an orthopedic specialist. They can determine the best surgical and non-operative treatments for your condition. Also read our FAQ on spine surgery.

If you’re going to have spinal surgery, there are steps you can take to be prepared for a successful procedure and recovery.