Spinal cord. HE (1). Very low magnification image showing a cross-sectioned rabbit spinal cord. The gray matter is located internally, and consists of two anterior horns (A) (more widened and separated from the surface of the medulla), and two posterior horns (P) (which sharpen posteriorly and practically contact the surface of the organ). The white matter, is located outside the gray matter, and can be divided into two anterior (Ca), two lateral (Cl) and two posterior white columns (Cp). (G: spinal ganglion, slightly displaced forward due to rupture of the posterior root on that side. Rp: dorsal roots. Ra: ventral roots. Red arrowheads: posterior medial sulcus. Blue arrowheads: anterior medial fissure. M: meninge (dura). Arrow: ependymal canal).
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Spinal cord. HE (2). 4x. The gray matter consists of two anterior horns (A) (more widened and separated from the surface of the medulla), and two posterior horns (P) (which sharpen posteriorly and practically contact the surface of the organ). The white matter, is located outside the gray matter, and is divided into columns: two anterior (Ca), two lateral (Cl) and two posterior (Cp). The gray matter of the two halves of the spinal cord, is in contact both in front and behind the ependymal canal (E), through the anterior (red arrow) and posterior (blue arrow) gray commissures, respectively. (Red arrowheads: posterior median sulcus. Blue arrowheads: anterior medial fissure).
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Spinal cord. HE (3). 10x. Central region of the spinal cord showing the ependymal canal (E), lined by the ependyma or ependymocyte cells, whose cilia (arrowhead) are visible. Immediately behind the ependymal duct is the posterior gray commissure (blue asterisk) and, beyond, the two posterior columns (Cp) of the white matter. Ahead of the ependymal duct is the anterior gray commissure (red asterisk) (narrower than the posterior one), the anterior white commissure (cb), and the two anterior white columns (Ca). (Red arrow: posterior median sulcus. Blue arrow: anterior median fissure).
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Spinal cord. HE (4). 10x. In the anterior horn of the gray matter of the spinal cord, the presence of large neuronal somas, belonging to motor neurons (blue arrowheads), stands out. The thin expansions (red arrowheads) that radiate from the gray matter of the anterior horn, entering both the lateral (Cl) and anterior white columns (Ca), correspond to axon bundles of root neurons (of motor neurons and, in the D1 to L2 metameres, also of vegetative preganglionic neurons; these do not appear in the image). (Cp: posterior column).
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Spinal cord. HE (5). 20x. Anterior gray horn of the spinal cord showing the big and star-shaped motor neuron somas (blue arrows). They have a large, spherical euchromatic nucleus and thick Nissl bodies in the cytoplasm. There are also other neurons (blue arrowheads) of much smaller size. The smallest nuclei, scattered by the neuropil, belong to different types of glial cells. The white matter (Sb) has many central myelinated nerve fibers (red arrowheads) cross-sectioned. There are bundles of motor neuron axons (red arrows) that enter the white matter from the gray matter.
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Spinal cord. HE (6). 10x. The white matter (Sb) of the spinal cord is made up of central myelinated nerve fibers that, as were grouped in both ascending and descending fascicles, always appear cross-sectioned in a cross section of the spinal cord (they appear as a point surrounded by a clear halo). There are also fine bundles of nerve fibers (arrowheads), corresponding to axons of motor neurons (and vegetative preganglionic neurons in metameric D1 to L2), which run parallel of the cut plane, and which end up leaving the spinal cord, constituting the anterior root (Ra). Above, to the left, there is a small portion of the anterior gray horn (asterisk). The thick septum of fibrous connective tissue visible in the lower part of the image corresponds to the meninge (M), specifically to the dura.
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Spinal cord. HE (7). 10x. The end of the posterior gray horn of the spinal cord almost contact with the surface of the organ. This image shows the apex or vertex (asterisk) of the posterior horn, highlighting the small size of the numerous neuronal somas located there. Note how the dorsal root (Rp), made up of nerve fibers from the dorsal root ganglion, is penetrating the spinal cord, establishing the border between the posterior (Cp) and lateral (Cl) columns of the white matter.
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Spinal cord. Cresyl violet (1). Low magnification image of a cross-sectioned rat spinal cord. Cresyl violet is a basic aniline that stains cell nuclei and the Nissl bodies of neurons. Therefore, the gray matter, located internally, is easily differentiated with this technique. It consists of two anterior gray horns (A) (more widened and separated from the surface of the medulla), and two posterior horns (P) (which are sharpened posteriorly and practically contact the surface of the organ). The white matter, on the contrary, stains very little. It is located outside the gray matter, and shows two anterior columns (Ca), two lateral columns (Cl) and two posterior columns (Cp). (Arrow: ependymal canal).
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Spinal cord. Cresyl violet (2). 10x. With this technique, the gray matter is distinguished by the presence of neuronal somas, easily identifiables by the staining of its Nissl bodies. The image shows the anterior gray horn (A), with large motor neurons (blue arrowheads). Other structure observed are part of the posterior gray horn (P), with smaller neurons, and portions of the anterior (Ca), lateral (Cl) and posterior (Cp) white columns. The small cell nuclei that are visualized in these columns correspond mainly to glial cells (also present in the gray matter). The gray matter of both spinal cord halves contact both in front and behind the ependymal canal (E), through the gray commissures anterior (red arrow) and posterior (blue arrow), respectively. (Red arrowheads: anterior medial fissure. Asterisk: white commissure, located between the anterior gray commissure and the bottom of the anterior medial fissure).
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Spinal cord. Cresyl violet (3). 20x. Anterior gray horn of the spinal cord, in which abundant star-shaped neuronal somas appear, mostly large, corresponding to the motor neurons (arrows) of the anterior horn. They have large Nissl bodies and an euchromatic nucleus (red arrowhead) with a striking nucleolus. Small neural somas (blue arrowhead) could belong to Golgi II neurons (such as Renshaw neurons). Cell nuclei without appreciable cytoplasm, scattered among neuronal somas, would correspond to various types of glial cells.
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Spinal cord. Cresyl violet (4). 40x. Motor neurons of the anterior gray horn of the spinal cord. The one that occupies the centre of the image is characteristic: a large star-shaped soma, with large Nissl bodies, an euchromatic nucleus (arrow) and developed nucleolus (next to the nucleolus you can see a small Barr body). Cell nuclei without appreciable cytoplasm (arrowheads), scattered among neuronal somas, correspond to various types of glial cells.
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Spinal cord. Cresyl violet (5). 100x. High magnification micrograph showing motor neurons of the anterior gray horn of the spinal cord. The one on the right shows all the typical features: a large, star-shaped soma with large Nissl bodies, an euchromatic nucleus (blue arrow) and a developed nucleolus. The two neuronal processes (red arrows) that are observed must be classified as dendrites, since they have Nissl bodies (arrowheads). Remember that the axon is free of Nissl bodies. (A region of the soma devoid of Nissl bodies is observed in the neuron on the left: it is the axon hillock (asterisk).
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Spinal cord. Cresyl violet (6). 100x. High-magnification image of a motor neuron of the anterior gray horn of the spinal cord. The star-shaped soma has large Nissl bodies, as well as an euchromatic spherical nucleus (n) and a highly developed nucleolus (arrow). The tiny spherical formation attached to the nucleolus corresponds to the sex chromatin or Barr's body (red arrowhead), so it follows that the sample is from a female animal. The thick prolongation that, emerging from the soma, goes to the right is a dendrite, since it presents Nissl bodies (blue arrowhead). The small nuclei, of different shapes and sizes, surrounded by barely perceptible cytoplasm, correspond to glial cells.
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Spinal cord. Cresyl violet (7). 10x. Image of the posterior gray horn, which contact with the surface of the organ. The posterior horn has a large number of neuronal somas: In the apex o vertex, they are small somas (red asterisk), while those located more anteriorly (blue asterisk) are larger. In the upper part of the image, the dorsal root (Rp) can be seen penetrating the spinal cord. To the right and left of the posterior horn, both the posterior white column (Cp) and the lateral white columns (Cl) can be seen.
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Spinal cord. Cresyl violet (8). 20x. The end of the posterior horn of the spinal cord contact with the surface of the organ. In this image, the apex or vertex of the posterior horn can be seen, the small size of the numerous neuronal somas located there stands out. Note how the dorsal root (Rp), made up of nerve fibres coming from the spinal ganglion, is penetrating the spinal cord. This establishes the border between the posterior (Cp) and lateral (Cl) white columns.
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Spinal cord. Klüver-Barrera (1). Low magnification micrograph showing a cross- sectioned spinal cord at the level of the cervical region (note the predominance of the transverse diameter). The Klüver-Barrera technique incorporates both cresyl violet (stains the neuronal Nissl bodies) and luxol blue (stains myelin bright blue). For this reason, the white matter, with its anterior (Ca), posterior (Cp) and lateral (Cl) columns, is intensely stained. The large amount of myelin in the gray matter (Sg) is also striking. The pale regions, in the form of a cap or inverted letter "V", located in the most dorsal area of both posterior gray horns, correspond to the gelatinous substance of Rolando (R), very poor in myelin. (A: anterior gray horns. P: posterior gray horns. Red arrow: central canal).
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Spinal cord. Klüver-Barrera (2). 4x. The gray matter of the spinal cord has, although less than the white matter, an abundant amount of myelin fibers, as demonstrated by the staining performed with the Klüver-Barrera technique (luxol blue stains myelin of the nerve fibers in bright blue color). In the gray matter, the neuronal somas are stained in violet colour by cresyl violet, being larger those of the anterior gray horns (A) and notably smaller those of the posterior ones (P). In the center of the medulla is the central or ependymal canal (E), flanked, in front and behind, respectively, by the gray commissures, anterior (a) and posterior (p). (R: Rolando's gelatinous substance. Ca: anterior columns. Cl: lateral columns. Cp: posterior columns. Red arrow: anterior median fissures. Blue arrows: posterior medial septum).
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Spinal cord. Klüver-Barrera (3). 10x. Ependymal or central canal (E), lined by ependymocytes, flanked by the gray commissures, anterior (a) and posterior (b), which put in contact the gray matter of both spinal cord halves. The white commissure (Cb) is located between the anterior gray commissure and the bottom of the anterior medial fissure (red arrow). Note the distribution of neural somas in the gray matter, with the anterior ones being larger (red arrowhead) and the posterior ones smaller (blue arrowhead). (Ca: anterior columns. Cp: posterior columns. Blue arrow: posterior median septum).
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Spinal cord. Klüver-Barrera (4). 10x. Anterior horn of the gray matter of the spinal cord. In addition to the motor neuron somas (arrowheads), the abundance of myelin nerve fibers in the gray matter is striking. These fibers seem to run without apparent order, either individually or grouped into small packages. Groups of fibers (arrows) are observed that radiate from the gray matter to the white matter. (Ca: anterior white column. Cl: lateral white column).
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Spinal cord. Klüver-Barrera (5). 20x. Anterior gray horn of the spinal cord, showing several motoneuron somas (red arrows), star-shaped. These neurons have large Nissl bodies, an euchromatic nucleus and a developed nucleolus. In the neuropil, the large number of myelin nerve fibers (stained bright blue by luxol blue), which run in apparent disorder, is striking. Sometimes they are grouped into small packages, some of which (blue arrows) can be seen leaving the gray matter and moving to the white matter, to finally constitute the anteriosr root (not visible in the image). (Sb: white matter).
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Spinal cord. Klüver-Barrera (6). 40x. Gray matter of the anterior horn of the spinal cord, showing several motoneuron somas (red arrows), large and star-shaped. These neurons have large Nissl bodies, an euchromatic nucleus, and a developed nucleolus. In one of these motor neurons, along with the nucleolus, a structure compatible with the accessory body of Cajal (arrowhead) can be seen. Other smaller neurons (blue arrows) are also seen. The smallest cell nuclei, surrounded by almost imperceptible cytoplasm, correspond to different types of glial cells. In the neuropil, there are many myelin nerve fibers (stained bright blue by luxol blue) that run, isolated or grouped in small packages, in apparent disorder.
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Spinal cord. Klüver-Barrera (7). 10x. In some areas, the limit between the gray and white matters appears to blur. Thus, on the outer edge of the neck of the posterior horn, the reticular formation (FR) is located, appearing as a network, formed by thin septa of gray matter (recognizable by the presence of neuronal somas) intermingled with small bundles of white matter (more stained in blue colour due to the greater abundance of myelin fibers). In the upper part of the image, both to the right and to the left, we can see (very pale) the Rolando's gelatinous substance (asterisks).
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Spinal cord. Klüver-Barrera (8). 10x. The apex of each of the posterior gray horns appears dorsally covered by a pale region, in the form of a cap or inverted letter "V": it is the gelatinous substance of Rolando (R), very poor in myelin, and therefore weakly stained with the luxol blue of the Klüver-Barrera technique. It is a sensory nucleus of the posterior horn, in which there are numerous small neurons. Likewise, it appears crossed by small bundles of myelin nerve fibers (arrows). The image also shows the white matter, both the posterior (Cp) and the lateral columns (Cl).
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Spinal cord. Silver stain (1). Low magnification image of a cross-sectioned rat spinal cord at the level of the lumbar region. Note the great development of the gray matter, with very wide anterior (A) and posterior (P) gray horns. Even at this low magnification, the motor neuron somas (red arrowheads) are distinguishable, as well as other somas (blue arrowheads) located more posteriorly, also of large size that could correspond to neurons of the Clarke's column. The white matter is subdivided into two anterior columns (Ca), two lateral ones (Cl) and two posterior ones (Cp). (Red arrow: ependymal canal. Blue arrow: anterior median fissure).
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Spinal cord. Silver stain (2). 10x. Portion of the anterior gray horn (A) of the spinal cord, in which the large and star-shaped somas of the motor neurons (arrowheads) stand out. Groups of axons (nerve fibers) (red arrows) of these neurons (also of vegetative preganglionic neurons in the D1 to L2 metamers) radiate from the outer limit of the gray matter, completely crossing the thickness of the white matter (Sb), and they leave (blue arrow) the spinal cord to converge several of them and constitute the anterior root (asterisk).
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Spinal cord. Silver stain (3). 20x. Motor neurons (arrows) of the anterior gray horn of the spinal cord. With this silver technique it is possible to visualize the neuronal extensions much better than with the anilines. These cells have a large, star-shaped soma, from which various extensions start that can be followed. The neuropil appears furrowed by fine nerve fibres, stained in a dark color, which would correspond to axons of the motor neurons themselves, or to axons from neurons located in other regions, both medullary and extramedullary.
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Spinal cord. Silver stain (4). 40x. Motor neurons of the anterior horn of the spinal cord, viewed at high magnification. With this technique, the abundant neurofibrils that intersect in the soma and continue through the extensions (both dendrites and axon) are revealed. The soma of these neurons is stellate, voluminous, from which several extensions arise that can be followed for a more or less long way. The nucleus is not stained, it appears pale, although it is possible to identify the nucleolus (arrowhead) inside. The thicker neural extensions, emerging as "pinches" of the soma, are dendrites (red arrows). One of the neurons exhibits a fine extension from its origin, that possibly corresponds to an axon (blue arrow).
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Spinal cord. Silver stain (5). 100x. Motor neuron of the anterior horn of the gray matter of the spinal cord seen at very high magnification, with the oil-immersion objective. Its soma is large and stellate in shape, from which various extensions emerge that can be identified either as dendrites (d) (the thickest, multiple, emerging as "pinches" of the soma), or as axon (a) (unique, relatively fine since its emergence, barely branched and gradually thinning). Note the network of neurofibrils (arrowhead) in the cytoplasm of the neuron. The neuropil appears furrowed by fine nerve fibers that would correspond both to axons of the motor neurons themselves, and to axons from neurons located in other regions, either medullary or extramedullary.
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Spinal cord. Silver stain (6). 20x. In this high magnification of figure 2, a small portion of the anterior horn (A) can be seen with some motor neurons (blue arrow). Groups of axons (nerve fibers) (red arrows) of these neurons (and of vegetative preganglionic neurons in the D1 to L2 metamers) radiate from the outer limit of the gray matter, crossing the white matter (Sb) and leaving (asterisk) the spinal cord to converge several of them and constitute the ventral root (Ra).
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Spinal cord. Silver stain (7). 4x. Low magnification image of a cross sectioned rat spinal cord at the level of the lumbar region. Note how, on both sides, the dorsal roots (Rp) (consisting of the central branches of the "T" division of the spinal ganglion neuron axons) are penetrating the spinal cord. At this point, the border between the lateral column (Cl) and the posterior column (Cp) of the white matter is established. (A: anterior gray horns. P: posterior gray horns. Ra: ventral roots).
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Spinal cord. Silver stain (8). 10x. High magnification of the previous figure. The dorsal root (Rp), made up of the central branches of the "T" division of the spinal ganglion neuron axons, is penetrating (asterisk) into the spinal cord. Already inside the spinal cord, in a narrow region between the apex of the posterior gray horn and the medullary surface, small bundles of nerve fibers (arrows) are seen that will end up either making synapses with sensory neurons of the posterior gray horn (P), or by entering the posterior column (Cp) to form part of ascending nerve pathways.
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Spinal ganglion. HE (1). Low-magnification image of a cross sectioned spinal cord showing one of the two spinal ganglia (G) in this spinal cord segment. Note its relationship to the dorsal root (asterisk) of the spinal cord. It is slightly more displaced forward than it should because the posterior root appears to have been torn. (Arrow: dura mater).
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Spinal ganglion. HE (2). 4x. At low magnification and when the orientation of the section plane is appropriate, it is possible to observe the peripheral location of the neuronal somas (blue arrows), among which areas occupied by nerve fibers appear (red arrow). Note the dorsal root (asterisk), emerging directly from the ganglion. (Me: spinal cord. D: dura mater).
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Spinal ganglion. HE (3). 10x. In the upper part of the image, the dorsal root (asterisk) is emerging from the node, confirming that the spinal ganglion is in the path of the dorsal root. The somas of the pseudomonopolar neurons (arrowheads) are located in the ganglion, mainly peripherally. It is possible to see in the centre of the ganglion, groups of neuronal somas intermingled with areas where nerve fibers are concentrated (arrows) when the section plane is not strictly central and longitudinal. On the left, there is a fine connective tissue capsule that surrounds the ganglion. (D: dura mater).
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Spinal ganglion. HE (4). 20x. The spinal ganglion neurons are pseudounipolar neurons, with globular or piriform soma, which in the histological sections adopts a rounded shape and a smooth contour. They can appear as large neurons (red arrows), with fine Nissl substance, and smaller ones (blue arrows), in which the staining of the somatic cytoplasm is uniform and the Nissl bodies are not distinguished. The small, slightly flattened, heterochromatic nuclei that surround neuronal somas correspond to the satellite glial cells (also called satellite cells) (arrowheads). Clusters of these nuclei are frequently seen, adjacent to a neuronal soma: in each of these groups the "glomerulus" is located (asterisks).
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Spinal ganglion. HE (5). 40x. The pseudounipolar neurons of the spinal ganglion have a globular or piriform soma, which appears rounded in histological sections, although sometimes it takes on a polygonal shape when it is compressed by neighbouring neuronal somas. Large neurons (red arrows) show fine Nissl bodies well visible. In other smaller neurons (blue arrows), the staining of the somatic cytoplasm is uniform and the Nissl substance is either do not distinguish, or is restricted to the outermost area of the soma. The small, slightly flattened, heterochromatic nuclei that form like a crown around neural somas belong to the satellite glial cells (blue arrowheads). Clusters of these nuclei are frequently seen, adjacent to a neuronal soma: in each of these groupings the "glomerulus" is located (asterisks). To the left of the image there is an area with nerve fibers (F). (Red arrowheads: starting cone of axon. C: connective tissue capsule of ganglion).
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Spinal ganglion. HE (6). 100x. The center of the image shows the soma of a typical large pseudounipolar neuron, seen at very high magnification. It has a rounded (N) euchromatic nucleus and developed nucleolus. The fine Nissl bodies are homogeneously distributed throughout the somatic cytoplasm. The elongated zone devoid of Nissl substance located on the right side of the soma corresponds to axon (A), which seems to surround the soma. The small and flattened nuclei, with heterochromatin, which are surrounding both the neural somas and the axon, belong to the satellite glial cells (arrows). Clusters of these nuclei are frequently seen, adjacent to a neuronal soma: in each of these groupings the "glomerulus" (G) is located.
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Spinal ganglion. HE (7). 100x. Pseudounipolar spinal ganglion neuron seen at very high magnification. It has a rounded euchromatic central nucleus (N) and an evident nucleolus. Fine Nissl substance is observed, distributed homogeneously throughout the somatic cytoplasm except in the area of the axon hillock (blue asterisk). It can be seen the emergence of the axon (blue arrow), showing fine lines that correspond to groups of microtubules. Immediately to the left, a glomerulus (G) can be seen, with several sections of the axon (red arrowheads) accompanied by several nuclei belonging to satellite glial cells ("periaxonic gliocytes") (red arrows). It can be seen the fine connective tissue "capsule" (blue arrowheads) that completely surrounds neuronal soma and satellite cells, leaving the glomerulus itself confined within it. (Red asterisk: satellite glial cell - "perisomatic gliocyte" - D: fibrous connective tissue of the dura mater).
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Spinal ganglion. Cresyl violet (1). 4x. Spinal ganglion observed at low magnification. With this basic aniline, the Nissl substance of neurons, as well as the cell nuclei (both heterochromatin and nucleolus) are very well stained. The somas of the pseudounipolar neurons (arrowheads) are located mainly peripherally, although when the cut plane is not strictly central and longitudinal, groups of neuronal somas intermingled with nerve fibers (arrows) are seen in the centre of the ganglion. Below and to the left is a portion of the dorsal root (Rp). (Me: spinal cord).
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Spinal ganglion. Cresyl violet (2). 10x. The spinal ganglion neurons are pseudounipolar neurons, with globular or piriform soma, which in the histological sections adopts a generally rounded shape and a smooth contour. There are large neurons (red arrows), with fine visible Nissl substance, and smaller ones (blue arrows), in which the staining of the somatic cytoplasm is uniform and the Nissl substance is barely distinguishable. The small flattened heterochromatic nuclei, that surround the neuronal somas correspond to the satellite glial cells (red arrowheads). In the upper left part of the image, the dorsal root (Rp) is observed. Both in the root and in the areas of the interior of the ganglion occupied by nerve fibers, the elongated nuclei (blue arrowheads) belong to Schwann cells, as well as endoneural connective tissue fibroblasts.
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Spinal ganglion. Cresyl violet (3). 20x. The pseudomonopolar neurons of the spinal ganglion have somas of highly variable sizes. There are large somas (red arrows), with fine visible Nissl substance, and others of medium or small size (blue arrows) in which the cytoplasm staining is uniform and Nissl substance is more difficult to distinguish. In many cases, a reinforcement (blue arrowhead) of the basophilia is observed in the periphery of the soma. The small flattened heterochromatic nuclei, that surround the neuronal somas, or forming part of the glomerulus (G), correspond to the satellite glial cells. In the areas of the interior of the ganglion occupied by nerve fibers, the elongated nuclei belong to both Schwann cells (the palest) and endoneural connective tissue fibroblasts. (Red arrowheads: axon hillock).
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Spinal ganglion. Cresyl violet (4). 40x. The spinal ganglion neurons are of the pseudounipolar type. The cell nucleus (N) is characteristic: large, spherical, euchromatic and with a developed nucleolus. In the cytoplasm, the typical image of fine Nissl substance (blue arrow) stands out, especially in the larger somas, while in the smaller neuronal somas, the Nissl substance is difficult to distinguish, frequently appearing an edge (red arrow) of basophilic material on the periphery of the soma. The small flattened heterochromatic nuclei, that surround the neuronal somas, or forming part of the glomerulus (G), correspond to the satellite glial cells (arrowheads). The elongated nuclei that appear in the clear spaces between the neuronal somas are both Schwann cells and connective tissue fibroblasts. (Asterisks: axon hillock).
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Spinal ganglion. Cresyl violet (5). 40x. The pseudounipolar neuron in the centre of the image has a large (N) nucleus (euchromatic and with a developed nucleolus) and a cytoplasm with typical fine Nissl substance. On the left side of the soma there is a pale area devoid of Nissl substance, the axon hillock (red asterisk) and, next to it, a glomerulus (G), with multiple sections of the axon (arrows) grouped in a reduced space and closely related to the satellite glial cells (in this case "periaxonic gliocytes") (red arrowheads). The rest of the neuronal somas are of medium/small size. The areas (blue asterisk) devoid of neuronal somas are occupied by nerve fibres, making it possible to distinguish nuclei from Schwann cells (larger and paler) and endoneural fibroblasts. (Blue arrowhead: "perisomatic gliocyte").
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Spinal ganglion. Cresyl violet (6). 100x. Very high magnification image of three pseudounipolar neurons. The two on the right are medium and small, while the middle one (with fine Nissl substance) is large. In the last, we do not see the nucleus since the section plane has not affected it, but instead highlights an axon hillock (asterisk), devoid of Nissl substance and - next to it - three sections of the axon (Ax) are observed that correspond to a glomerulus. The small flattened heterochromatic nuclei, that surround the neuronal somas, or forming part of the glomerulus (G), correspond to the satellite glial cells (red arrows). In the lower right part of the image, the relatively large, pale and elongated nuclei are probably Schwann cells.
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Spinal ganglion. Cresyl violet (7). 100x. High magnification image of the soma of a typical large pseudounipolar neuron. Note the euchromatin nucleus (N), with a very striking nucleolus (n). The somatic cytoplasm is fully occupied by fine Nissl substance (arrowhead). The nuclei (red arrows) of the small satellite glial cells, somewhat elongated and of relatively heterochromatic nucleus, are appreciated. There are some flattened nuclei, located immediately outside the satellite glial cells: they correspond to fibroblasts (blue arrows) of the fine connective tissue “capsule” that completely surrounds the neuronal soma and its glomerulus.
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Spinal ganglion. Cresyl violet (8). 100x. Soma of a large pseudounipolar neuron. The nucleus (N) is rounded, ,euchromatic and with a developed nucleolus (n). Abundant fine clumps of Nissl substance (arrowhead) occupy the entire somatic cytoplasm, but are absent from the axon hillock (asterisk) and from the axon itself (Ax), which is seen emerging to the right and downward. The nuclei of the satellite glial cells are visible (arrows), surrounding the neuronal soma. They are somewhat ovoid in shape, with relatively dense heterohromatin.
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Spinal ganglion. Klüver-Barrera (1). 4x. Low-magnification image of a spinal ganglion stained with the Klüver-Barrera technique. In the pseudounipolar neurons (arrow) the Nissl bodies are stained with cresyl violet. The nerve fibres (asterisk) appear bright blue, as luxol blue stain myelin. Note how the neuronal somas are located mainly peripherally (in the cortex of ganglion, C), due to the orientation of the section plane. (M). On the left, the dorsal root (R) can be seen emerging from the ganglion. (M: middle region of the ganglion).
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Spinal ganglion. Klüver-Barrera (2). 20x. It is in the periphery or cortex (C) of the ganglion (located in this image on the right) that the somas of pseudomonopolar neurons are mainly located. In the center or medulla (M), the predominant element are myelinated nerve fibers (red arrows), although among them there are also neurons. This is due both to a certain irregularity of the cortico-medullary boundary and to the orientation of the section plane. The pale halo that appears surrounding many of the neuronal somas is an artefact of the technique.
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Spinal ganglion. Klüver-Barrera (3). 40x. High magnification showing neuronal somas (arrows) with fine Nissl bodies, stained purple with cresyl violet. The myelinated nerve fibers (asterisks), stained bright blue with luxol blue, correspond to the axon of these neurons.
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Spinal ganglion. Silver stain (1). 10x. Pseudounipolar neurons (arrows) of a spinal ganglion stained in dark brown with a silver technique. In many of the neuronal somas it is observed how the only prolongation or axon they emit, as soon as it emerge form the soma, makes a series of turns on itself, constituting the so-called "glomerulus" (arrowheads). Among the groups of neuronal somas, there are areas (asterisk) where nerve fibers accumulate, originated by the division in T (at a certain distance from the glomerulus) of the axon of each one of these neurons.
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Spinal ganglion. Silver stain (2). 20x. Somas of pseudounipolar neurons (S). In many of them it is observed how the axon, as soon as it originates from the soma, makes a series of turns on itself, of greater or lesser complexity, to constitute the so-called "glomerulus" (arrows). (F: areas where nerve fibers accumulate).
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Spinal ganglion. Silver stain (3). 40x. Several somas of pseudomonopolar neurons (S) in which the axon emerges from the soma, and gives rise to the glomerulus (blue arrows). Some of these glomeruli are of extraordinary complexity (asterisk). Note that sometimes the axon (red arrow) that comes out of the soma does not form a glomerulus, but runs more or less rectilinear. (F: nerve fibers).
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Spinal ganglion. Silver stain (4). 40x. Small group of pseudomonopolar neuron bodies (S) flanked, on both sides, by nerve fibers (F). Several glomeruli can be seen (arrows). Immediately to the right of this group of neurons it is possible to see the exact point where an axon is dividing in a "T" (arrowhead).
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Spinal ganglion. Silver stain (5). 40x. Nerve fiber bundle in a spinal ganglion. They always belong to the unique extension or axon of pseudounipolar neurons and their corresponding "T" division. Note how the calibre of these nerve fibers is highly variable: the large (blue arrow) and medium (red arrow) fibers are myelinated; the thinnest (arrowhead) would be fine myelinated fibers or -even- unmyelinated. Below and to the right is the soma of a pseudounipolar neuron (S).
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Spinal ganglion. Formol-uranyl nitrate technique (1). 20x. A spinal ganglion stained with the Cajal formol-uranyl nitrate technique. Numerous pseudounipolar neurons (arrows) are observed, as well as areas where nerve fibers accumulate (F). This technique reveals the Golgi complex (blue arrowheads) impregnated with a dark brown color, which is distributed throughout the neuronal soma except at the level of the axon hillock (red arrowheads), where it is absent.
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Spinal ganglion. Formol-uranyl nitrate technique (2). 40x. High magnification of the previous figure. The Golgi complex (blue arrows) is revealed with this histological technique, appearing as a complex network of anastomosed canaliculi. It is distributed throughout the soma of pseudomonopolar neurons, except in the region of the axon hillock or origin of the axon (red arrow), where it is absent. (N: neuronal nucleus. F: nerve fibers).
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Sympathetic ganglion. HE (1). Human. 2x. Very low magnification image of a sympathetic ganglion. The neuronal somas are distributed throughout the ganglion, so that - unlike the spinal ganglion - there is no cortex or medulla. Between the somas of the sympathetic neurons (which show a certain tendency to form small groups) there are extensive areas (asterisks) where nerve fibers accumulate. Although it is not possible to see it at this magnification, there are also satellite cells that surround each neuron, as well as a connective tissue endoneurium related to nerve fibers. On the outside, the ganglion is lined by a thin connective tissue capsule (C).
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Sympathetic ganglion. HE (2). Human. 4x. The neuronal somas (arrowheads) of the sympathetic ganglion are irregularly distributed, although they tend to form small groups. There are also large areas (F) devoid of neuronal somas, where nerve fibers are grouped. On the right side of the image, especially in the lower half, there are several thick bundles (asterisks) of nerve fibres entering/leaving the node.
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Sympathetic ganglion. HE (3). Human. 10x. Vegetative neurons (arrows) distributed without an apparent order, among a large number of nerve fibers (F). Most neuronal somas are slightly retracted due to a fixation problem, so there is a small clear space around them. Note the nuclei of satellite glial cells that surround the somas of these autonomic neurons.
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Sympathetic ganglion. HE (4). Human. 20x. Sympathetic neurons separated by nerve fibres (F) and connective tissue septa in which blood vessels are seen (V). The somas of these neurons have a spherical euchromatic nucleus, which is sometimes displaced (red arrowhead) from the centre of the cell. In the somatic cytoplasm there are fine Nissl substance not very evident, which sometimes tend to be located (blue arrowhead) on the periphery of the soma. It is not uncommon to find variable amounts of a brownish-yellowish pigment in the soma of vegetative neurons (arrows). It can be both melanin and lipofuscin. Special techniques are required to determine its nature.
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Sympathetic ganglion. HE (5). Human. 40x. The somas of the sympathetic neurons have a spherical euchromatic nucleus and a developed nucleolus, sometimes displaced from the centre of the cell. In the somatic cytoplasm there are fine Nissl substance not very evident, which sometimes tend to be located (blue arrowhead) on the periphery of the soma. It is not uncommon to find variable amounts of a brownish-yellowish pigment (red arrows), which can be either melanin or lipofuscin. The soma of these neurons have processes (blue arrows), that cross both the satellite glial cell cover and the connective tissue capsule that surrounds the soma, to enter the territory of the nerve fibers. Among the neuronal somas are nerve fibers (F) and connective tissue with blood vessels (V).
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Sympathetic ganglion. HE (6). Human. 100x. Somas of various sympathetic neurons seen at high magnification. The euchromatic cell nucleus (N) is spherical, with a highly developed nucleolus (n). In the somatic cytoplasm, the Nissl substance sometimes tend to be located (arrowhead) on the periphery of the soma. All the somas that appear in the image show a greater or lesser amount of granules of a brownish-yellowish pigment (arrows), which can be either melanin or lipofuscin. Its exact nature cannot be determined with a simple hematoxylin-eosin. (F: territory where nerve fibres and connective tissue with blood vessels are located, as well as extracapsular dendrites of neurons).
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Sympathetic ganglion. HE (7). Human. 100x. High magnification showing four somas of sympathetic neurons. The cell euchromatic nucleus (N) is spherical, with a highly developed nucleolus (n). In the somatic cytoplasm, the Nissl substance sometimes tend to be located (blue arrowheads) on the periphery of the soma. Three of the four somas that appear in the image show a variable quantity of brownish-yellowish granules (blue arrows) of a pigment that can be either melanin or lipofuscin. A thick process (red arrow) emerges from the soma of one of these neurons, which crosses the capsule, and may be a long extracapsular dendrite. The neuron in the upper part of the image seems to emit several very fine extensions (red arrowheads), whose appearance is compatible with intracapsular dendrites. (Asterisk: satellite glial cell nucleus. F: territory where nerve fibres and connective tissue with blood vessels are located, as well as extracapsular dendrites of these neurons).
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Spinal ganglion. Silver stain (1). Human. 2x. Very low magnification image of a sympathetic ganglion. The neuronal somas are distributed throughout the ganglion, so that there is no cortex or medull. Between the somas of the vegetative neurons (which show a certain tendency to form small groups) there are extensive areas (asterisks) where large amounts of nerve fibres accumulate. On the outside, the node is lined with a thin connective tissue capsule (red arrow). Along the left side of this node, nerve fibre bundles are observed: two entering/leaving (Fn) the node, and three cut transversely (blue arrows).
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Spinal ganglion. Silver stain (2). Human. 4x. In this low-magnification image of a sympathetic ganglion, it is possible to observe how the neuronal somas emit various processes of variable length. Between the somas of the sympathetic neurons there are extensive areas (asterisks) where large amounts of nerve fibers accumulate, impregnated in black or very dark brown colour by silver.
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Sympathetic ganglion. Silver stain (3). Human. 10x. The sympathetic neurons (arrowheads) have a rounded soma from which emerge - without hardly deforming it - multiple processes (one axon and multiple dendrites of variable length). These neurons appear irregularly distributed, with a certain tendency to form small groups. Among them there are extensive areas devoid of somas, in which large amounts of nerve fibres (F) impregnated in a black or very dark brown colour by the silver technique.
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Sympathetic ganglion. Silver stain (4). Human. 20x. Sympathetic neurons showing rounded somas with a hole, that corresponds to the "negative" image of the nucleus. From this soma, and without hardly deforming it, multiple dendrites (blue arrowheads) of variable length arise, and a single axon (difficult to identify with certainty). Several of the neuronal somas accumulate varying amounts of a granular substance (red arrowheads) stained black: it could correspond to either melanin or lipofuscin. Above and to the right is a thick connective tissue septum (C), showing collagen fibres that form light brown wavy bundles. (Arrow: binucleated sympathetic neuron. F: areas devoid of neuronal somas, where nerve fibers are concentrated).
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Sympathetic ganglion. Silver stain (5). Human. 20x. The soma of the sympathetic neurons is rounded and shows multiple dendrites (blue arrowheads) of variable length, and a single axon (difficult to identify with certainty). Long dendrites of two or more nearby neurons approach until they meet, to form the so-called "glomerulus" (G), where multiple synaptic contacts are established. Several of the neuronal somas shown in the image accumulate varying amounts of black granules (red arrowheads): they could be either melanin or lipofuscin. Among the neuronal somas, the fine wavy lines stained black can correspond both to axons (nerve fibers) (from neurons of this ganglion, from another, or from vegetative preganglionic neurons), as well as to long dendrites.
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Sympathetic ganglion. Silver stain (6). Human. 40x. Detail of the previous image, showing a glomerulus (G) consisting of the confluence of long dendrites of two neurons. Note how the soma of these vegetative neurons is rounded, without deformations, despite emitting multiple extensions (one axon and several dendrites of variable length).
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Sympathetic ganglion. Silver stain (7). Human. 40x. The soma of the sympathetic neurons is rounded, and emits several processes: one axon, difficult to identify with certainty, and multiple dendrites of variable length. Dendrites are classified as long or extracapsular (blue arrows) (those that cross the capsule (arrowhead) of satellite glial cells surrounding the soma) and short or intracapsular (those that do not). Sometimes fine nerve fibers are seen that are in close contact with the neuronal soma: these would be afferent nerve fibres (red arrow) that will synapse with the soma. In the lower part of the image, appears a typical glomerulus (G), made up by the confluence of long dendrites of two neurons. On the right is a thick connective tissue septum (C), with wavy bundles of collagen fibres.
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Sympathetic ganglion. Silver stain (8). Human. 40x. Sympathetic neurons are multipolar, and their dendrites can be either long or extracapsular (blue arrowheads) or short or intracapsular (red arrowheads). In the centre of this image, long dendrites (blue arrows) from at least three vegetative neurons come together to form a glomerulus (G). Above and to the left is a neuron in which the capsule (red arrow) that intimately surrounds the neuronal soma is visible.
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