In lower concentrations, extra-adrenal chromaffin cells also reside in the bladder wall, prostate, and behind the liver. Ĭhromaffin cells also settle near the vagus nerve and carotid arteries. These terms can be used interchangeably but usually paraganglioma refer to a tumor originating from chromaffin cells outside the adrenal gland, which can also be called extra-adrenal pheochromocytoma, whereas pheochromocytoma typically refer to a tumor originating from the chromaffin cells within the adrenal gland. Tumors arising from these cell are called paragangliomas or pheochromocytomas.

The largest extra-adrenal cluster of chromaffin cells in mammals is the organ of Zuckerkandl. Ģ) Chromaffin cells (or pheochromocytes): These cells will migrate to the area adjacent to the sympathetic ganglia (hence the name paraganglia) and to the adrenal medulla where they will be the most abundant type of cells. A tumor arising from these cells is called neuroblastoma. Some of these cells will migrate to the adrenal medulla to form sympathetic ganglia cells within the adrenal medulla (without postsynaptic sympathetic fibers). From these ganglia, the post synaptic sympathetic fibers will arise and extend toward their target organ. There are two types of cells that originate from the neural crest and are related to the sympathetic nervous system (originate from a cell called sympathogonia): ġ) Neuroblasts: These cells migrate, during the fourth to the fifth week of fetal development in humans, on both sides of the spinal cord toward the region just behind the dorsal aorta forming the two chains of sympathetic ganglia (Sympathetic chain).

Hence they are called neuroendocrine cells. The chromaffin cells release catecholamines: ~80% of adrenaline ( epinephrine) and ~20% of noradrenaline ( norepinephrine) into systemic circulation for systemic effects on multiple organs (similarly to secretory neurones of the hypothalamus), and can also send paracrine signals. This causes the release of catecholamines. In order to activate chromaffin cells, the splanchnic nerve of the sympathetic nervous system releases acetylcholine, which then binds to nicotinic acetylcholine receptors on the adrenal medulla. They are in close proximity to pre-synaptic sympathetic ganglia of the sympathetic nervous system, with which they communicate, and structurally they are similar to post-synaptic sympathetic neurons. These cells serve a variety of functions such as serving as a response to stress, monitoring carbon dioxide and oxygen concentrations in the body, maintenance of respiration and the regulation of blood pressure. Chromaffin cells, also called pheochromocytes (or phaeochromocytes), are neuroendocrine cells found mostly in the medulla of the adrenal glands in mammals.

Primary function of the adrenal gland