"Thoracic segments" refer to the sections of the spine located in the upper and mid-back region. These segments are connected to the ribs and serve to protect vital organs such as the heart and lungs. Full definition
Sympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord in the intermediolateral cell column (or lateral horn), beginning at the first thoracic segment of the spinal cord and are thought to extend to the second or third lumbar segments. (sciencedaily.com)
Since flies have legs only in thoracic segments, the presence of neuroblasts in these segments indicates the coordination of neurogenesis with development of the body plan at the stem - cell level,» says James Truman, co-author of the study. (sciencedaily.com)
In these animals, the first few thoracic segments have appendages that look like those of the head. (uchospitals.edu)