The lumbar vertebrae are five bony cylinders found in a person's lower back between the thoracic vertebrae and the sacrum, according to Innerbody and Spine-Health. The lumbar vertebrae are larger and heavier than other vertebrae because they must bear the weight of the upper body while at the same time allowing it to bend and twist.
Also, the lumbar vertebrae protect the spinal nerves, though the spinal cord does not pass through the lumbar spine, according to Spine-Health. Instead, the spine branches into nerves called the cauda equina. This part of the spine also gently curves inward.
The lumbar vertebra is made up of a vertebral body and a number of projections called processes, according to Innerbody. One is the spinous process, which is above the vertebral body and separated from it by a space called the vertebral foramen. This space allows the spinal nerves to pass.
Lumbar vertebrae are also different from the other vertebrae in the spine because they lack the facets found on either side of the cervical and thoracic vertebrae, according to Innerbody. They also lack the smaller openings called the transverse foramen.
In between the vertebrae is a disc made of cartilage, says Innerbody. This disc, which has a spongy center called the nucleus pulposus, not only acts as a shock absorber but joins the vertebrae to each other.