THE FASCINATING WORLD OF ELECTRON MICROSCOPY: ULTRASTRUCTURAL MORPHOLOGY OF ADRENAL CHROMAFFIN CELLS

Adrenal medulla, part of sympathetic nervous system derived from neural crest cells, is composed of short interconnecting cords or clumps of secretory cells called chromaffin cells that are modified sympathetic postganglionic neurons without process (they lost their axons and dendrites during embryonic development). The chromaffin cells have abundant membrane-bound granules with diameter of 100 to 350 nm. In humans, two populations of chromaffine cells are distinguished by transmission electron microscopy (TEM): one population secreting epinephrine (E) and one population secreting norepinephrine (NE) (Fig.1). These cells differ by the nature of their membrane bound granules