The lumbar spine is the lowest five of the twenty-four vertebrae of the spine, which descend vertically from the bottom of the ribs to the top of the hips and pelvis. Structurally, the lumbar spine is the foundation for the body’s movement and supports the weight of the upper body as it moves through space. It is prone to injury because it is where the most weight-bearing and movement of the body takes place.
The lowest and widest bone of the column is the L5, with large amount of ligamentation towards the fused sacrum and the posterior, superior portion of the iliac crest, or hip plate. As one descends down the vertebrae, the pedicles of each bone get longer and deeper as the spinal cord widens. The vertebrae have 5 wide fins, called processes, two transverse processes, two articular processes, and the spinous process at the very rear of the vertebrae. The spinal cord passes through the vertebral foramen which is the chamber formed by the processes at the back of the bone.
The Ligaments of the Lower Back
There are multiple ligaments connecting each vertebrae and interlacing down into the sacrum. The lumbar portion of the spine is the least able to twist as it is primarily a support structure for the body. Each bone of the Lumbar is wider and deeper than the last, allowing for less movement and more stability as you descend down to the pelvis. The backsides of the vertebrae interlace with ligaments and tendons that stabilize the trunk. The psoas muscles run up the lumbar vertebrae on each side up to the L1. The Lumbar is the third and final curve in the spine, with ligaments interlacing down into the sacrum and up into the thoracic spine and ribs.
The Nerves of the Lumbar Spine
The lumbar spine is particularly important for the nervous system; it is the starting point for the nerves of the legs and lower body and contains a plexus of nerve connections that extend up the spinal cord, and down into the legs and lower organs. This is a pivot place for alignment of the entire body; oftentimes nerve pain originates from mis-alignment in the lower back. The fins and processes at the back of the bones protect the nerves, but can be somewhat easily mis-aligned to pinch nerves in the legs and hips. This is why hip opening should be done slowly and why it is important to keep the sitting muscles (QL, spinal erectors, obliques) engaged and lengthening throughout hip opening.
Muscles of the Lumbar Spine
The muscles that interlace in the Lumbar spine are intricate and not usually appreciated by the term spinal erectors. The spine seems to be perfectly capable of strengthening itself to stay erect, if you engage the obliques, transverse abdominus, the muscles that run up the spinal vertebrae, and the serratus posterior inferior muscles connecting to the lumbar vertebrae from the ribcage.
That concludes the final piece of anatomy of the spine. Hope you enjoyed the series, parts 1 and 2 are available by clicking on the numbers. Let me know if you want me to write about anything else in the spine!