Summary
The synganglion is bounded by an extracellular sheath and is divided into the cortex and the neuropile. The cortex contains two glial layers, each of which is composed of a distinctive type of glial cell, and three types of neurons. Type I is the least common and most electron dense, type II is most common, and type III represents neurosecretory cells with a larger volume of cytoplasm than in types I and II. Substantial areas of the neuron cell bodies are unsheathed. A third type of glial cell is found in the neuropile.
The first glial layer of the cortex, the perineurium, lies beneath the extracellular sheath and overlies the neuron cell bodies contributing to their ensheathment. In areas lacking neuron cells bodies, the perineurium overlies a second glial layer, the subpermeurium, which is inflected inwards where a group of neuron cell bodies is encountered. The subperineurium contributes to the ensheathment of both the cell bodies of neurons and the nerve fibers. It is confluent with glial cells which arise within the neuropile. The neuropile contains nerve fibers and glial cells and is perforated by the esophageal canal, which is lined by the perineurium and subperineurium. Unsheathed nerve fibers contact each other in three ways: end-knob, longitudinal, and cross contacts.
Zusammenfassung
Das Synganglion wird von einer extrazellulären Scheide umkleidet und ist in Cortex und Neuropil gegliedert. Der Cortex enthält zwei Gliazellschichten (die jeweils durch einen bestimmten Zelltyp charakterisiert sind) und drei Typen von Neuronenzellkörpern. Neuronenzellkörper vom Typ I sind sehr elektronendicht und nur selten anzutreffen; Typ II ist am häufigsten vertreten; Typ III wird durch neurosekretorische Zellen repräsentiert, die zudem ein relativ größeres Plasmavolumen als Typ I und Typ II besitzen. Ausgedehnte Bereiche der Neuronenzellkörper sind nicht umhüllt. Außerdem wurde ein dritter Gliazelltyp im Neuropil gefunden.
Die äußere corticale Gliaschicht, Perineurium genannt, liegt unter der extrazellulären Scheide und überdeckt die Neuronen teilweise. In Gebieten, in denen Neuronenzellkörper fehlen, überlagert das Perineurium eine zweite Gliazellschicht, das Subperineurium. Diese Schicht kann sich ins Innere des Ganglions erstrecken, falls sie auf eine Neuronenzellkörpergruppe stößt. Das Subperineurium trägt sowohl zur Umhüllung der Neuronenzellkörper, als auch der Nervenfasern bei. Es steht in direktem Zusammenhang mit Gliazellen aus dem Inneren des Neuropils.
Das Neuropil umfaßt Nervenfasern und Gliazellen und umgibt den ösophagealen Kanal, welcher vom Perineurium und Subperineurium gebildet wird. Hüllenlose Nervenfasern treten in drei Arten miteinander in Verbindung, durch Endknöpfe, Längs- und Querkontakte.
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Supported in part by U. S. Public Health Service Research Grant EC-246 from the Environmental Control Administration, Training Grant ES-00069 from the National Institute of Environmental Health Sciences and by the Office of Naval Research. Paper No. 3320 of the Journal Series of the North Carolina State University Agricultural Experimental Station.
We are indebted to Dr. R. F. Foelix for supplying the German translation of the summary and for reading the manuscript.
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Coons, L.B., Axtell, R.C. Cellular organization in the synganglion of the mite Macrocheles muscaedomesticae (Acarina: Macrochelidae). Z.Zellforsch 119, 309–320 (1971). https://doi.org/10.1007/BF00431289
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DOI: https://doi.org/10.1007/BF00431289