vertebral arch of twelfth thoracic vertebra
A neural arch forming the posterior bony ring of the twelfth thoracic vertebra, composed of pedicles and laminae enclosing the spinal canal at the thoracolumbar junction. T12 is the most atypical thoracic vertebra; its arch bears mamillary and accessory processes resembling lumbar features, lacks transverse costal facets, and its inferior articular facets adopt the lumbar sagittal orientation.