The lowest part of the spine is called the lumbar spine. This area usually has five vertebrae. However, some people are born with a sixth vertebra in the lumbar region.
At the base of the lumbar spine is a group of specialized vertebrae that connects the spine to the pelvis. This is called the sacrum. When one of the bones forms as a vertebra rather than part of the sacrum, it is called a transitional (or sixth) vertebra.
The lumbar spine is shaped like a backwards C, The vertebrae in the lumbar spine area are the largest of the entire spine. The lumbar spinal canal is also larger than in the cervical (neck) or thoracic (torso) parts of the spine.
The lumbar spine is vulnerable to back pain imply because it carries most of the burden of your weight bearing body movements. Attempting to carry or lift an object that is too heavy usually causes injuries to the lumbar spine.