What is the paraganglion system?

The adrenal medulla is embryologically, functionally, and structurally distinct from the adrenal cortex. It is populated by cells derived from the neural crest (chromaffin cells) and their supporting (sustentacular) cells. The chromaffin cells, synthesize and secrete catecholamines in response to signals from preganglionic nerve fibers in the sympathetic nervous system. Similar collections of cells are distributed throughout the body in the extraadrenal paraganglion system. The most important diseases of the adrenal medulla are neoplasms: Neuronal neoplasms (neuroblastomas and more mature ganglion cell tumors) and neoplasms composed of chromaffin cells (pheochromocytomas).