Paraganglia


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Paraganglia

 

a series of endocrine glands of vertebrate animals and man that are composed of chromaffin (adrenal) tissue and that secrete adrenaline (epinephrine), noradrenaline (norepinephrine), and possibly other catecholamines into the blood. In man and mammals paraganglia include very small nodules as well as large encapsulated, lobulated aggregates, which have an organ structure. The largest paraganglia are the medullary portions of the adrenal glands; substantially smaller are the carotid paraganglion and the paraganglia located near the heart and aorta. The components of paraganglia are secretory cells, of at least two types, and auxiliary cells, which are enclosed in connective-tissue stroma. The hormone is stored in cytoplasmic granules. Upon excitation (depolarization) of the cell membrane, it is secreted by evacuation of the granule contents into the extracellular medium. The biochemical and pharmacological characteristics of the secretory cells of paraganglia are similar to those of some neurons, especially sympathetic ones, in which noradrenaline is the mediator and which, in the opinion of a number of scientists, share a common embryonic origin with paraganglial cells. The auxiliary, or lining, cells cytologically resemble neuroglia. A unique feature of paraganglia is that their secretory cells are directly innervated, that is, they are innervated by efferent (motor) nerve endings. Functionally and genetically, paraganglia are a single system that cannot be divided into chromaffin (“sympathetic”) and nonchromaffin (“parasympathetic”) parts. The erroneous distinction of nonchromaffin paraganglia led to denial of their secretory function and to the notion that the carotid paraganglion, for example, functions as an organ of chemical sense. It is now established that all paraganglia have a single type of chemistry, which is adrenaline-related, and that the innervation of paraganglial secretory cells is efferent.

REFERENCES

Smitten, N. A. Simpato-adrenalovaia sistema v filo- i ontogeneze pozvonochnykh. Moscow, 1972.
Coupland, R. E. The Natural History of the Chromaffin Cell. London, 1965.

D. A. SAKHAROV

References in periodicals archive ?
Pheochromocytoma and paraganglioma are relatively uncommon tumors of neuroendocrine origin that arise from neural crest-derived chromaffin cells of the adrenal medulla and sympathoadrenal and parasympathetic paraganglia, respectively.
2) Paraganglioma is a kind of tumour that arises from extraadrenal paraganglia and consists of specialized neural crestderived cells.
Most of these are catecholamine-secreting tumors and primarily located in the abdomen (more rarely in the chest) in the extraadrenal paraganglia, whereas the remainder are generally non-catecholamine secreting and mostly located in the head and neck paraganglia (5).
1 Mediastinal paragangliomas are predominantly concentrated in two locations; the aorticosympathetic paraganglia of the posterior mediastinum or the autonomic ganglia in the superior and middle mediastinum.
The third and final part of the book is made up of various real-world cases, including adrenal and paraganglia diagnosis, anterior mediastinal mass diagnosis, appendix diagnosis, and several other examples.
Tympanic paragangliomas are neuroendocrine neoplasms located in the middle ear and arising from chromaffin cells of the parasympathetic paraganglia.
Although it develops at the sites of normal paraganglia mainly intraabdominally, glomus jugularae or carotid bodies; it may be found in other part of the body also.
Phaeochromocytomas are neuro-endocrine catecholamine-secreting tumours that arise from chromaffin cells of the adrenal medulla or sympathetic paraganglia.
Paragangliomas are rare tumors of the parasympathetic and sympathetic paraganglia.
Pheochromocytomas are uncommon tumors arising from the adrenal medulla and the sympathetic paraganglia.
The normal paraganglia consists of nests of chief cells (type1) and sustentacular cells (type 2).
2) Paragangliomas are highly vascular and slow growing tumors (5 mm annually) deriving from the paraganglia, which are specialized tissue of the extra-adrenal neuroendocrine system.