The phylum Chordata is a taxonomic group. All animals which have a  spine, or backbone, are classified in the phylum Chordata. There  are three subphylums in Chordata: Uroch â¦ ordata (tunicates),  Cephalachordata (lancelets), and Vertebrata (vertebrates).
The 12 vertebrae in the upper back make up what is known as the thoracic spine. They curve outward and inward to provide structure for the rib cage. The bones provide structure and flexibility for the body, while protecting the spinal colu... Read More.
Overview. 1  The thoracic spine is the mid-portion of your back and extends from the base of the neck to the bottom of the rib cage. It is made up of 12 thoracic vertebrae, which are separated by soft spongy discs that aid in shock absorption. 2  Degenerative disc disease (DDD) is a process that breaks down the inter-vertebral discs.