Cells originating from the neural crest of the thoracic region migrate to form bilateral sympathetic chains on each side of the vertebral column. Some cells give rise to the preaortic ganglia and sympathetic organ plexuses. Nerve fibers from the intermediate horn of the thoracolumbar spinal cord penetrate the ganglia and the sympathetic chains.

1. Preaortic ganglion
2. Sympathetic ganglion
3. Organ plexus
4. Developing suprarenal gland
5. Dorsal root ganglion
6. Neural tube
7. Dorsal aorta
8. Urogenital ridge
9. Notochord
10. Gut