Lumbar Spine

Low Back Anatomy

Have you ever asked, "Why do so many people suffer from low back pain?" The answer involves a brief overview of the lumbar spine. Although the entire spine is involved in everyday activities of rest and movement, the low back can be vulnerable to many pain-provoking disorders. Simple sprains and strains from overexertion, a herniated disc from a slip and fall, degenerative disc disease or spinal stenosis from normal aging, and other disorders can cause low back pain.

To help you understand back pain, the following brief and illustrated anatomy lesson is provided. 

What Is the Lumbar Spine?

The lumbar spine (low back) is the third major region of the spine; it is below the cervical spine and thoracic spine (Figure 1). Most people have five bones (vertebrae) in the lumbar spine, although it is not unusual to have six. Each vertebra is stacked on top of the other and between each vertebra is a gel-like cushion called an intervertebral disc. The discs help to absorb pressure, distribute stress, and keep the vertebrae from grinding against each other.

spine, lateral and posterior views
Figure 1. Spinal Column

Ligaments and Tendons: Connective Lumbar Spine Soft Tissues

The vertebrae and discs are held together by groups of ligaments (Figure 2). Ligaments connect bone to bone, whereas tendons connect muscle to bone. In the spine, tendons connect muscles to the vertebrae. The ligaments and tendons help to stabilize the spine and guard against excessive movement in any one direction.

Figure 2. Spinal Ligaments

Lumbar Spine Joints

The spine also has joints that are similar to knees, elbows, and other joints. The spinal joints are called facet joints (Figure 3).

The facet joints have been described as finger-like, and they link the vertebrae together. The facet joints are located at the posterior area of the spinal column (on the back side of the spinal column).

In addition, the facet joints help to make the spine flexible and enable you to bend forward, backward, and side to side.

facet joint, rear view
Figure 3. Spinal Facet Joints

Spinal Cord and Spinal Nerves in the Lumbar Spine

spinal nerve structures
Figure 4. Spinal Nerve Structures

In the center of the spinal column is a vertical hole called the spinal canal; it contains the spinal cord. The bones that create the spinal canal serve as armor to help protect the spinal cord from injury.

The spinal cord descends from your brain, through the cervical and thoracic spines in the spinal canal.  It ends, usually, in between the first and second lumbar vertebrae; below that, a group of nerves called the cauda equina (which translates to "the horse's tail) travels through the spinal canal and branch off to various parts in the lower half of your body.

The spinal cord and the nerves (Figure 4) are part of the central nervous system that includes the brain. The nerves are the body's neural message system, and they help you move, feel, and experience sensations such as heat.

Lumbar Spine Anatomy Helps You Understand Low Back Pain

Now that you have learned about lumbar spine anatomy, perhaps you can better understand what's causing your low back pain.  The lumbar spine is an intricate system, and an injury to the vertebrae (eg, spinal fracure) or to the discs (eg, herniated disc) can cause pain.



Updated on: 10/22/12
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