Which part of the spine is not one of the four main divisions?

The spine is traditionally organized into four main divisions: cervical, thoracic, lumbar, and sacral (which includes the coccyx). The cervical region consists of the first seven vertebrae, responsible for supporting the head and allowing for neck mobility. The thoracic section comprises twelve vertebrae that articulate with the ribs and provide structural stability to the upper body. The lumbar region encompasses five vertebrae known for their larger size and weight-bearing capacity, which supports much of the body's load. The sacrum is made up of five fused vertebrae and is connected to the coccyx at the distal end.

The pelvic region, while important for overall anatomy, does not represent a distinct division of the spine. Instead, it refers to the structure that supports the spinal column and connects to the lower limbs but does not include any vertebrae associated with the spinal divisions. This distinction is crucial in anatomy, especially in understanding spinal structure and function. Thus, the pelvic region is not recognized as one of the primary divisions of the spine.