Why part of the spine bends and part of it does not?

The spine is divided into regions with different structural characteristics: the cervical, thoracic, lumbar, sacral, and coccygeal regions. The thoracic region has rib attachments, providing stability and limiting movement, while the cervical and lumbar regions are more flexible and designed for greater mobility. The intervertebral discs and the orientation of the facet joints also contribute to the varying degrees of flexibility throughout the spine. Consequently, some parts can bend more easily, while others are more rigid for support.