Functional state of sympathoadrenal system

Like the posterior lobe of the pituitary gland, the adrenal medulla is a derivative of the nerve tissue. It can be considered as a specialized sympathetic ganglion. Accumulations of chromaffin tissue are found in the sympathetic nervous system( paraganglia).A chain of chromaffin bodies is located anterior to the abdominal aorta, in the region of the aortic bifurcation;carotid bodies also form part of the chromaffin system of the body.

Chromaffin adrenal cells secrete mainly adrenaline and to a lesser extent norepinephrine, whereas postganglion cells of the sympathetic nervous system are predominantly norepinephrine.

The similarity of products and ways of responding to the sympathetic nervous system and the adrenal medulla was the basis for combining these structures into a single sympathoadrenal system with the release of the nervous and hormonal link.

Chromaffin cells and sympathetic ganglion cells are formed in embryogenesis from embryonic neural crest cells, called sympathogens. These cells serve as precursors of sympathoblasts( from which the cells of sympathetic ganglia develop) and pheochromoblasts( giving rise to chromaffin cells).Chromaffin cells can develop a pheochromocytoma. Other types of neural crest develop from other types of catecholamine-producing tumors:

■ from sympatoblasts - sympathoblastoma;

■ from pheochromoblasts - pheochromoblastoma;

■ from the cells of the sympathetic ganglion - ganglioniroma.

Tumors of the first two species are called neuroblastomas, the third - gang-glioneuroma( ganglioneuroblastoma).These types of tumors are observed in newborns and young children, and very rarely in adults. Neuroblastomas are more often found at the age of 1-3 years, this is a very malignant tumor. At least 50% of these tumors are located in the abdominal cavity( up to 35% in the adrenal glands).Ganglioneuroblastoma is formed by the transformation of neuroblastoma cells, contains both neuroblasts and ganglion cells at different stages of differentiation. Ganglio-neuroma is a benign tumor consisting of mature ganglion cells.

In adults, the most commonly observed pheochromocytoma, formed from chromaffin cells. In 90% of cases, the catecholamine-producing tumor of chromaffin tissue is localized in the adrenal medulla, and in 10% outside of these glands. Malignant are less than 10% pheochromocytomas.

With chromaffin tumors of the adrenal and adnadrenal localization, a large amount of adrenaline and no-radrenaline enters the bloodstream. This causes the emergence of hypertensive crises against the background of normal arterial pressure( paroxysmal form of the disease), persistently high blood pressure and periodically recurring against this background an even greater increase in pressure( mixed form);resistant arterial hypertension without crises( permanent form).

To assess the functional state of the sympathoadrenal system, use a whole range of indicators. However, only some of these markers are used in clinical practice, mainly for the diagnosis of pheochromocytoma. Approximately 1 of 200 patients with high blood pressure is diagnosed with pheochromocytoma.