Your lower back (lumbar spine) is much stronger than you think. It is highly flexible with a broad range of motions. Specifically, weight-bearing and sturdy.
However, the lumbar spine is commonly injured. And if you understand lower back anatomy, it can help you identify serious problems.
Important Lower-Back Anatomy:
Lordotic Curve: The lower back (lumbar) is the portion situated between your lowest rib and the buttocks. The lumbar spine has a natural curve, its called the lordosis, and it is responsible for:
- Reducing the concentration of stress to the lower spine
- Evenly distributing weight from the upper body
- Balancing the weight of your head
Any problems in the lumbar spine area can increase this excessive inward curvature, which will trigger pain and discomfort.
Vertebrae: Your lower back contains five vertebral bones stacked over each other. These bones are L1 through L5 and progressively increase in size. This allows them to bear weight more efficiently. The vertebrae protect nervous tissue, such as the spinal cord and cauda equina.
Discs: There are five intervertebral discs between each of the vertebrae. These act as a cushion and shock-absorber to protect your vertebrae during spinal movements.
Facet joints: Vertebrae are connected by joints. These paired facet joints provide stability and allow your spine to move in different directions. The joint surface is lined by cartilage, which provides smooth movement. The facets of the upper lumbar vertebrae are similar to the thoracic facet joints. Similarily, allowing for back-and-forth movements. However, the lower lumbar facets are more flexible and allow for side-to-side movement.
Supporting muscles: There are large muscles and intricate ligament networks in your lumbar spine. Being that, they stabilize the spine and orchestrate any twisting and bending movements.
Nerves in the Lumbar Spine
Along with the vertebrae and discs, there are five lumbar spinal nerves L1 through L5. They exit through the small holes in the vertebrae, emerging out of the spine at the nerve roots. Then they travel down each leg and are formed by sensory and motor fibers. Sensory fibers send messages to your brain when you feel pain. While motor fibers receive messages from the brain to prompt an action.
The lumbar spinal nerves increase in size progressively and perform functions, such as:
- L1: provides sensation to your groin and genital region. They may also contribute to hip muscle movement.
- L2, L3, and L4: provides sensation to the front of your thigh and along the inside of the lower leg. They also control hip and knee muscle movement.
- L5: provides sensation to the outer lower leg and the upper part of the foot. And the web-spacing between the first and second toes. This nerve also controls the hip, knee, foot, and toe movements.
The L4 and L5 spinal nerves work with others contributing to the formation of the sciatic nerve. This nerve is the largest in the body. The sciatic nerve runs from your rear pelvis to the back of your leg. It then ends in your foot.
The Spinal Cord and Cauda Equina
The spinal cord starts in your brain and travels the length of your spine. Eventually, ending in the upper region of your lumbar, called the conus medullaris. However, after this point, the spinal nerves descend downward. The hanging position of the nerves resembles a horse’s tail, called the cauda equina. The spinal cord, conus medullaris, and cauda equine are vital tissues. These tissues need protection. Damage or compression to these requires immediate medical attention.
By understanding the basic anatomy of the lumbar spine (lower back), you can better identify problem areas. Whereas, you can more easily differentiate between problems that commonly affect the lumbar, such as sciatica and localized muscle pain. Knowing the lumbar spinal structure will also help you better communicate with your doctor.