The lumbar spine is made up of vertebrae found in the lower back, says Spine-health. These vertebrae curve in toward the abdomen and begin 5 or 6 inches below the scapular bones. Doctors refer to these vertebrae alphanumerically as L1 through L5.
The vertebrae in the lumbar spine must bear a great deal of weight and must help the body twist, bend and lift heavy weights, making them vulnerable to break-down and injury, says Spine-health. The lumbar vertebrae are stacked on top of each other, with a disc of spongy material between them. The discs protect the bones from shocks and from scraping against each other. They also allow the spine to be flexible.
Two vertebrae that are adjacent to each other are connected by small facet joints, which also allow the spine to be flexible, notes Spine-health. The spinal column near the lumbar vertebrae also holds nerves that branch out from openings in the spine. Eventually, these nerves come together to form the sciatic nerve, which bifurcates and runs down the back of each thigh, down the legs and to the feet.
Muscles also support the lumbar spine, says Healthline. They are the multifidus, the longissimus and the spinalis. The multifidus stabilizes the lower spine and allows it to rotate. The longissimus starts in the middle of the lumbar spine and reaches up to the transverse process, and the spinalis muscle travels from the sacrum beneath the lumbar spine all the way to the cervical vertebrae in the neck.