The five lumbar vertebrae (vertebrae lumbales) of the human body form part of the spinal column. Because the lumbar spine has to bear a special load due to the weight and mobility of the trunk, damage or impairment to the lumbar vertebrae often leads to massive pain.
What are lumbar vertebrae?
In humans, the lumbar spine is composed of five lumbar vertebrae and is located in the lower part of the spine. It begins below the thoracic spine and runs to the sacrum (Os sacrum). Compared to the other vertebrae of the spine, the lumbar vertebrae are larger and all have a similar basic shape that resembles a bean. They are numbered from cranial (that is, from above or up toward the head) to caudal (that is, down toward the feet) from one to five. The fifth lumbar vertebra may be fused with the first vertebra of the sacrum, which is called sacralization. Seen from the side, the spine is slightly curved. This curvature is called lordosis in a normal condition. When the curvature is increased, the result is a hollow back or what is called hyperlordosis. The opposite of this is the flat back.
Anatomy and structure
Each lumbar vertebra consists of a lumbar vertebral body (corpus vertebrae), the lumbar arch (arcus vertebrae), four small vertebral joints, the spinous process (processus spinosus), the transverse process (processus transversus), and the vertebral foramen (foramen vertebrale). The vertebral arch is connected to the vertebral body by two strong feet, the pediculi arcus vertebrae. Together, the vertebral body and vertebral arch form the vertebral foramen. The spinous process sits on the vertebral arch, and the auxiliary process (processus accessorius) arises from below the vertebral arch and is found only in the lumbar vertebrae. In addition, the four articular processes (processus articularis superior and cranialis and processus articularis inferior and caudalis) are located on the vertebral arch on both sides at the top and bottom, providing a mobile connection to the vertebrae above and below. To the side of the superior articular process is also the teat process (processus mamillaris). On both sides of the lumbar vertebrae is the transverse process, which is comparatively long in the lumbar vertebrae. Together with the vertebral arches, the vertebral holes of adjacent vertebral bodies form a bony canal, the vertebral canal, which is also known as the spinal canal or spinal cord canal. There are also openings between adjacent vertebral bodies from which spinal cord nerves can exit.
Function and tasks
The lumbar spine is responsible for carrying the entire weight of the trunk and passes this weight to the sacrum. It stabilizes the trunk and enables the body to stand upright. The lumbar spine can be moved in different directions, allowing for different movement patterns. Mainly bending and straightening movements as well as movements to the side are possible. Here, flexion and extension of 70 degrees is possible in a healthy lumbar spine. To the side, an inclination of 25 degrees is possible. Only rotational movements are possible to a limited extent due to the structure of the vertebral bodies and the position of the vertebral joints. The rotational capacity is therefore only about two degrees. The mobility of the spine decreases with age. The intervertebral discs (Disci intervertebrales) located between the individual lumbar vertebrae have a buffering function. The lumbar vertebrae are surrounded by the lumbar muscles, to which they provide attachment points. The muscles wrap laterally around the spinous processes. The lumbar spine cooperates with and is supported by the back muscles in their functions. Together with the intervertebral discs and the muscles, the lumbar vertebrae protect the spinal canal with the spinal cord running through it with nerves and vessels. In the adult human body, the spinal cord ends approximately at the level of the second lumbar vertebra. The spinal nerve roots, the cauda equina, are arranged in the shape of a horse’s tail below this. The intervertebral hole, or foramen intervertebrale, located between each two vertebrae allows passage of the respective spinal nerves.
Diseases and disorders
Back pain often affects the lumbar region of the spine because the lumbar spine is subject to the most stress. Back complaints of various causes are summarized under the lumbar spine syndrome, or LS syndrome for short.There is localized, usually dull and pulling back pain that can radiate to the tailbone and legs. The pain can be acute or chronic, depending on the cause. In lumbago, colloquially known as lumbago, acute low back pain occurs. Strong reflex muscle tension leads to restricted movement of the lumbar vertebrae and severe pain. Lumbago often occurs after lifting heavy loads, bending over or jerky movements, but it can also be caused by previous poor posture. Chronic low back pain can occur due to poor posture, inflammatory changes such as ankylosing spondylitis, or an increasing reduction in the size of the intervertebral spaces. Spondyloarthritis, which involves changes in the vertebral joints, can also lead to chronic low back pain. Damage to the intervertebral discs between the lumbar vertebrae can lead to a herniated disc, in which nerves or parts of the spinal cord are compressed by disc tissue, causing pain. Characteristic of a herniated disc is the radiation of pain into the leg. Severe squeezing of the cauda equina, for example due to a herniated disc, leads to neurological deficits. In spinal stenosis, the spinal canal is narrowed; in spondylolisthesis, interruptions of the vertebral arches cause instability of the lumbar vertebrae up to vertebral slippage. Scheuermann’s disease is a growth disorder of the spine that can lead to painful malpositions. Rarely, back pain occurs due to tumor disease.
