Lumbar Spine Anatomy
The lowest part of the spine is called the lumbar spine. This area usually has five vertebrae. However, sometimes people are born with a sixth vertebra in the lumbar region. The base of your spine, called the sacrum, is a group of specialized vertebrae that connects the spine to the pelvis. When one of the bones forms as a lumbar vertebra rather than part of the sacrum, it is called a transitional, or sixth, vertebra. This occurrence is not dangerous and does not appear to have any serious side effects.
The lumbar spine's shape has a lordotic curve, shaped like a backward "C." If you think of the spine as having an "S"-like shape, the lumbar region would be the bottom of the "S."