Chromaffin System

CHROMAFFIN SYSTEM, chromaffin organs, adrenal system, system of chromaffin organs, a name given according to Kon's proposal to a series of organs that selectively react with a change in color and other properties to the action of chromium in its salt solutions. When a solution of potassium dichromate is applied to the tissue of these organs, they become apparent, as they turn brown and become accessible to macroscopic and microscopic study. This specific reaction of the cells of chromaffin organs was first discovered in 1864 by Vvedensky in Russia and in 1865 by Henle in Germany. The method of staining and revealing chromaffin organs among surrounding tissues greatly advanced the study of this system of organs. In lower vertebrate animals, this system of organs is represented by small clusters of chromaffin cells located near each sympathetic ganglion of the sympathetic trunk. Thus, in these animals, these organs are metameric, corresponding to the metamery of the sympathetic ganglia of the sympathetic trunk; since chromaffin organs are topically related to these ganglia, they are also called paraganglia or usually paraganglia (see).

In higher vertebrate animals, the metameric arrangement of chromaffin organs is absent even in the embryonic period of development; throughout life or only in the childhood period, not all embryonic rudiments of these organs are preserved, but only several such paraganglia. These include: 1) several variable (childhood) (fig. 1) abdominal para-aortic paraganglia (fig.₂); 2) permanent, so-called carotid, or intercarotid glands; 3) the adrenal gland (its medullary layer) or adrenal paraganglia. The adrenal paraganglion acquires the greatest vital importance in all animals, starting from amphibians. In amphibians, the chromaffin adrenal gland fuses with tissue of another origin, a derivative of the epithelium lining the body cavity, the so-called interrenal tissue (see Adrenal glands, comparative anatomical data). The chromaffin and interrenal tissues, merging together, form in higher vertebrates a substance of a newly formed organ, absent in fish, i.e., the complex adrenal gland (see). As for the carotid glands, the question of their inclusion in the X. s. cannot yet be considered settled and is disputed by many authors (see Paraganglia). The organs of the X. s. mentioned develop from the rudiment of the sympathetic nervous system, i.e., they are sympathogenic organs; later, already in the embryonic period, the cells constituting this tissue lose all morphological signs of nerve cells and acquire a number of new features, among which their chromaffinophilia, argentaffinity, presence of adrenalogic granules, etc., stand out; morphologically they become sharply distinct from primitive sympathetic cellular elements. Therefore, such cells are called chromaffin (by Kohn) or phaeochromic (by Pol). In their protoplasm, specific granules appear, stained in brown and dark shades by solutions of chromium salts; it is precisely these granules that give a series of reactions of chromaffin organs (or similar tissues) to adrenaline; therefore, they are considered the morphological carriers of adrenaline or its unfinished intermediate products ('proadrenaline'). Thus, chromaffin cells by function and reactions are adrenalogic cells, and the entire X. s. of organs is the adrenal, or better, adrenalogic (producing adrenaline) system. Since all organs of this system have no open ducts (ductless organs), they are classified as endocrine organs; their intracellular products pass directly into the capillary and then into the venous system; the veins thus serve simultaneously as the excretory pathways for their complex secretions, mixed with blood (see Vegetative nervous system, as well as Internal secretion?). - Besides the adrenal glands and the carotid gland, all other, mostly unpaired, organs of the X. s. to one degree or another are subject to involution (reduction) with age, often ending in their disappearance. How absolute and final this disappearance of unstable, 'labile' organs of the adrenalogic system is, is still difficult to say. There is reason to believe that, although with age the paraganglia visible to the naked eye, located in certain places, disappear, nevertheless in certain nodes of the sympathetic nerve trunk and its branches, permanent microscopic inclusions of groups of adrenalogic cells remain and may later become specifically differentiated (Wiesel, Zalkind). The temporarily functioning organs of the adrenalogic system of organs are the following paraganglia of early childhood: 1) additional organs of the sympathetic nerve trunk - abdominal aortic paraganglia, paired or unpaired organs; 2) paraganglia laid in (sympathetic) solar plexus (unpaired or in the form of several separate chromaffin cell nests); 3) paraganglia scattered in various extra- and intra-organic nodes of the sympathetic nervous system; 4) additional adrenal glands, consisting of interrenal (cortical) and chromaffin tissues. In the relevant literature, unfortunately, there is no uniformity in the definition of the properties of the 'additional adrenal gland'. It is necessary to clearly distinguish 3 kinds of bodies, only partly similar to the true adrenal gland: 1) additional interrenal (cortical) bodies, 2) additional chromaffin bodies, 3) additional true adrenal glands. The first category of these are variable paraganglia subject to more pronounced age-related changes _than the permanent part of the X. s. In addition, chromaffin inclusions in the nodes of the sympathetic nervous system are also very variable, and this applies both to their position and to their form, size, and reactive properties. Permanent paraganglia, having reached maximum development, to a certain extent preserve, up to old age, the ratios of mass, form, and size. Their changes are more gradual than in childhood. The form, mass, size, as well as the structure of variable paraganglia, on the contrary, undergo continuous, profound changes both in the period of their development and in the subsequent period of their reduction. As for the zone of distribution of paraganglia in the body, as Wiesel points out, everywhere in sympathetic nerve nodes one can expect to find inclusions of groups of chromaffin cells by chance. These inclusions can be of various sizes: from a small group of cells to a macroscopically visible organ. In such large nodes of the sympathetic nerve as, for example, the solar plexus, these inclusions of chromaffin cells have a rather constant character. As for other nodes of smaller size, all of them have been insufficiently investigated in this respect. Nevertheless, in the specialized literature* there is a large number of articles devoted to individual findings of paraganglia or even entire additional adrenal glands in various parts of the animal body. Thus_g paraganglia have been found: in the composition of the spermatic cord, in the inguinal canal, in the appendages of the testicle, in the testicle itself, in the kidney, in the hepatoduodenal ligament, in the cardio-cervical region, in the solar plexus, at the aortic arch, in the wall of the esophagus, in the broad ligament of the uterus, in the uterosacral ligament. The greatest relative constancy is shown by paraganglia laid in the solar plexus, renal, superior mesenteric, hypogastric, in the plexus around the abdominal aorta. Very rare are findings of true additional adrenal glands, i.e., glands consisting of both epithelial and chromaffin tissue, like the adrenal gland, and not of just one of them. Due to the presence of small but numerous chromaffin inclusions (paraganglia) in the nodes of the sympathetic nerves, the X. s. as a whole represents a considerable mass of adrenalogic tissue, broken into separate links and scattered throughout the blood vessels, digestive tract, etc. The presence in the human body of relatively constant additional paraganglia, as for example in the region of the solar plexus, at the bifurcation of the common carotid artery, etc., or periodic ones (for example, childhood paraganglia) makes possible their compensatory hypertrophy in case of underdevelopment, decrease, or cessation of function of the medulla of the adrenal glands. At autopsy, various age-related and pathological processes are sometimes found in the medulla of the adrenal glands, expressed by various morphological changes in chromaffin cells_g and loss by them of specific, secretory properties (in particular, loss of chromaffin reaction). It turns out that the given subject did not have in life symptoms of bronchial (Addison's) disease, usually accompanying destruction of the adrenal glands. In such cases, the indicated, sometimes life-saving compensatory hypertrophy of chromaffin tissue in the other healthy paraganglia takes place. Pathological growth of chromaffin tissue in different places of its localization leads to the appearance of neoplasms (paragangliomas), usually associated with proliferation of sympathetic nervous tissue as well (sympathomas) (see also Ganglioneuroma). Excessive growth of chromaffin cells can lead to excessive production of adrenaline in the body - hyperadrenalinemia, which in turn leads to disruption of the correlation of function of the X. s. with other organs of 'internal secretion. For the development, structure, position, and function of the most important individual organs of the X. s. (adrenal gland, carotid gland, paraganglia), see the respective entries. Some authors formerly included in the system of chromaffin organs the so-called coccygeal gland, or glomus (glomus coccygeum), located on the anterior surface of the coccyx. This is a small formation the size of a pinhead or slightly larger *»(up to the size of a pea). At present, it has been established that the genesis of the coccygeal gland is not directly connected with the sympathetic nervous system. The presence of chromaffin elements in it is also not proven. The epithelioid cells enclosed in this formation, whose function is still not understood, apparently represent reactively changed smooth muscle fibers belonging to the middle coat of precapillaries.

In the coccygeal gland, the rudimentary human tail artery (a. sacralis media, s. caudalis) ends in a plexus; the thin vascular network of this artery constitutes the main mass of the organ together with its connective tissue capsule and trabeculae. A special question concerns the so-called yellow (chromaffin) cells of the intestinal canal; these cells possess the basic characteristic microscopic reactions of chromaffin cells, but genetically and functionally they differ from sympathogenic chromaffin elements. The yellow cells were first discovered by Nicolas (1891) in the intestinal epithelium; somewhat later they were found and described by Kulchitsky and others. When these cells are fixed with chrome salts or impregnated with silver, they are selectively stained (hence the name yellow, or argentophilic cells). These cells have a special secretory function, which is not sufficiently clarified in essence. In humans, the mentioned yellow cells are found as a result of special staining among the epithelium throughout the intestine, in Brunner's glands, in the initial part of the pancreatic duct (Kull), in the hepatic duct, and in the wall of the small bile ducts. As a result of the blastomatous growth of these same cells, true tumors may develop.