PARAGANGLION (paraganglia; Greek para near + ganglion a nerve knot) — the bodies of endocrine system producing mainly catecholamines and at the same time being the additional bodies of a nervous system which are carrying out hemoretseptorny function.
The term is for the first time offered in 1903. A. Kohn. Items were selected in one group on the basis of ability of their cells to besiege salts chromic to - you. Due to this feature such cells and the fabric formed by them were called chromaffin.
The largest P. are epinephral — marrow adrenal gland (see) — and lumbar aortal P. (Tsukkerkandl's body); allocate also a microparaganglion — guttural, drum, jugular and many others. In the subsequent referred accumulations to P. similar with chromaffin cells in the form of glomes (see. Glome ), including the carotid Glome which is located in the field of division of the general carotid artery into outside and internal carotid arteries; nadserdechny, lying in the area of a pulmonary trunk and the ascending aorta. Chromaffin P. combined under the name «adrenal system» earlier. It was established that P.'s cells which are in the field of distribution of conductors of a parasympathetic part of the autonomic nervous system are not besieged by salts chromic to - you. It formed a basis for so-called not chromaffin P.' allocation unlike the chromaffin P. connected with a sympathetic part of the autonomic nervous system. However according to T. A. Grigorieva, N. A. Smitten, D. A. Sakharova, P.'s division into chromaffin and not chromaffin is not quite proved as functionally and genetically they form uniform system.
The issued P. for the first time appear at the lowest vertebrata and carry out hl. obr. receptor function. At the subsequent stages of phylogenesis, in addition to receptor, there is an incretory function P., and at mammals they become complex bodies with various functionality. The human embryo 30 mm long has isolated chromaffin P. which arose from the hro-maffinoblast migrating together with neuroblasts of a sympathetic part of the autonomic nervous system. Not chromaffin P. come from embryonal bookmarks on the course IX and X couples craniocereberal (cranial, T.) nerves. Thus, a paraganglion have a neurogenic origin.
Items are, as a rule, surrounded with the connective tissue capsule, from a cut in depth of body the trabeculas dividing accumulations rather large (diameter of 20 — 30 microns) of cells on segments or tyazh depart. In cytoplasm of chromaffin cells a large number of small granules (fig.) disseminated between a cytoplasmic reticulum and microtubules, containing adrenaline or noradrenaline is found (see. Catecholamines ). These granules are dissolved during the fixing (unless as the fixer salts chromic to - you are used).
At many animals in chromaffin P. distinguish two types of cells — adrenotsita and noradrenotsita. By quantity adrenotsita — the light cells with granules size apprx. 0,2 microns in the diameter containing adrenaline prevail. In cytoplasm of these cells there are a little mitochondrions (usually small sizes) and many free ribosomes and grains of a glycogen. Noradrenotsita contain sharply osmiofilny (more dark) granules containing noradrenaline. It is not possible to differentiate this two types of cells in P. of the person usually since cytoplasm of cells of P. of the person is sated with both light, and dark granules.
In not chromaffin P. along with typical large cells cells of the smaller sizes meet kernels of an oval form, to-rye belong, apparently, to a peripheral neuroglia. By means of luminescent microscopy in nodes of a sympathetic trunk, napr, in an upper cervical node, a significant amount of the cells considered the same as chromaffin is found.
Specific feature of an innervation of P. — the contact of preganglionic effector nerve fibrils with P.'s cells which is observed in sympathetic nerve knots. On P.'s cells centrifugal shoots of cells of side horns of gray matter of a spinal cord and vegetative kernels of the glossopalatine and wandering nerves come to an end. At the same time quite large terminations of efferent preganglionic fibers of rounded shape with a set of synoptic vesicles diameter — 40 — 60 nanometers densely adjoin to P.'s cells. The vascular network P. is well developed, the majority of their secretory cells adjoins walls of vessels.
The proximity of cells of P. to nervous cells and fibers testifies not only to their genetic, but also functional relationship. The myelin nerve fibrils getting into P. reach a limit with the pericellular terminations capable to perceive changes of chemical composition of fabric and blood. The important role in hemoretseptorny functions belongs to a carotid glome and nadserdechny P. Predpolagayetsya that not chromaffin P. cosecrete various polypeptide hormones which are not catecholamines. As well as chromaffin cells, they contain the enzymes capable to decarboxylize proteinaceous predecessors of these hormones. Such function, in particular, enterokhromaffinotsita possess went. - kish. path.
Bibliography: Grigorieva T. A. Innervation of blood vessels, M., 1954; Ivanov G. F. Nerves and sense bodys of cardiovascular system, M. — JI., 1945; Kupriyanov V. V. Nervous device of vessels of a small circle of blood circulation, JI., 1959; Sakovich JI. V. Innervation carotid paragangliyev person, Nauch. works Irkutsk, medical in-that, century 92, page 9, 1971; Smitten N. A. Sympathoadrenal system in filo-and ontogenesis of vertebrata, M., 1972; Cop land R. The natural history of the hro-maffin cells, L., 1965; K o h n A. Chro-maffine Zellen, Chromaffine Organe, Para-ganglien, Prag. med. Wschr., S. 325, 1902.
B. B. Kupriyanov.