The common embryogenesis of chromaffin cells and sympathetic ganglion cells from primitive cells of the neural crest

Although the adrenal medulla is well developed by 12 weeks of gestation, most of the chromaffin tissue in the fetus is present in scattered extramedullary paraaortic paraganglia, the largest of which are termed the organs of Zuckerkandl. After birth, these paraganglia gradually atrophy, disappearing by two to three years of age. The various tumors that can arise from any site along the migratory path of the cells of the autonomic nervous system are in boxes. The chromaffin cells located in the paraganglia predominantly produce norepinephrine while those in the adrenal medulla typically secrete a greater quantity of epinephrine than norepinephrine.