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Pituitary gland. HE (1). Human. Panorama. Low magnification image of a horizontal section of a pituitary gland. The pituitary is made up of two parts of very different origin: anterior pituitary or adenohypophysis (in which pars distalis, pars intermedia and pars tuberalis are distinguished), and neurohypophysis (comprising pars nervosa or posterior lobe, infundibular stalk, and median eminence). Both pars distalis (D) and pars nervosa (N) are clearly seen in the figure. Between both, a thin pars intermedia (blue arrow) hardly stands out. (Red arrow: a very thin connective tissue capsule).
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Pituitary gland. HE (2). Human. 4x. The pars distalis (D), on the left, has the typical appearance of a solid, cordonal endocrine gland (irregularly arranged cell cords, separated by vascular-connective tissue septa). On the right is the pars neuralis (N), with a very different histological aspect (reminiscent of nervous tissue). In the center of the image and arranged vertically, is the pars intermedia, very narrow, in which some Rathke cysts (arrowheads) can be seen.
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Pituitary gland. HE (3). Human. 10x. The pars distalis is made up of endocrine cell cords (asterisks) separated by connective tissue septa. Cell cords are several cells thick, and show cells with different stain affinity (acidophilic, basophilic, and chromophobic). The connective tissue septa have large-caliber blood capillaries (arrows), that occupy almost the entire volume of the septum. Due to their wide lumen, these blood vessels are classified as sinusoids. Since they have a fenestrated endothelium and a continuous basal lamina, both visible with electron microscopy, they are considered "fenestrated sinusoids".
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Pituitary gland. HE (4). Human. 10x. Endocrine cell cords of the pars distalis, showing the two most characteristic cell types: acidophilic cells (a), most abundant (stained red), and basophilic cells (b) (stained blue). With immunohistochemical techniques it is possible to differentiate the distinct cell types from one to the other, being named according to the hormone secreted. Thus, GH cells and PRL cells would correspond to acidophilic cells, while TSH cells, FSH / LH cells and ACTH cells form part of the basophil cell population. Arrows point to wide blood capillaries ("fenestrated sinusoids"), often occupied by numerous red blood cells.
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Pituitary gland. HE (5). Human. 20x. Acidophil (a) (GH and PRL cells) and basophil cells (b) (TSH, FSH / LH and ACTH cells) are mixed in the cell cords of the pars distalis, the former being considerably more abundant. There are cells with no stained cytoplasm: they correspond to the so-called "chromophobe cells" (arrowheads), many of which are related to the so-called "follicle-stellate cells". (Arrows: "fenestrated sinusoids", of very wide lumen).
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Pituitary gland. HE (6). Human. 20x. Acidophil (a) (GH and PRL cells) and basophil cells (b) (TSH, FSH / LH and ACTH cells) are mixed in the cell cords of the pars distalis, the former being more abundant. The cells in which no stained cytoplasm is seen are the "chromophobe cells" (arrowheads), many of which could correspond to the so-called "follicle-stellate cells". The arrow points to a small "micro-follicle", a rare finding in pars distalis. (S: "fenestrated sinusoids", of very wide lumen).
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Pituitary gland. HE (7). Human. 4x. Between the pars distalis (D) (left) and the pars neuralis (N) (right), is the pars intermedia (I), characterized by the presence of cavities, Rathke's cysts (arrows), covered by a cuboid epithelium and filled with a homogeneous, amorphous, colloid-like material. The cells of the pars intermedia, and sometimes also those of the cysts themselves, usually show basophilia (and are immunopositive for, among other substances, ACTH and MSH). It is not uncommon to see how some basophil cells of the pars intermedia, individually or in small groups, enter a small distance into the pars nervosa. This phenomenon is known by the name of "basophilic invasion" (asterisk).
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Pituitary gland. HE (8). Human. 10x. The pars intermedia (I) is a narrow strip made up of groups of cells and some cystic cavities, the Rathke cysts (arrows), covered by a cuboidal epithelium and filled with a homogeneous, amorphous material with a colloid appearance. The cells of the pars intermedia, and sometimes those of the cysts themselves, usually present basophilia, being immunopositive for, among other substances, ACTH and MSH. It is not uncommon to see how some basophilic cells of the pars intermedia, individually or in small groups, enter (arrowheads) a small distance into the pars nervosa. This phenomenon is known by the name of "basophilic invasion". (D: pars distalis; N: pars nervosa).
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Pituitary gland. HE (9). Human. 10x. The general appearance of pars nervosa is very reminiscent of that of nervous tissue. The dyeing appetite is very pale. It is made up of a large number of neuronal axons (they are bare axons), which come from neurons whose somas are located in the hypothalamus. In addition, there is a characteristic cell type, glial in character, the pituicytes, whose small heterochromatic nuclei, are distributed homogeneously, without special order. A few of those nuclei could actually belong to microglial cells. (Arrows: small blood vessels, loaded with red blood cells).
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Pituitary gland. PAS (1). Human. Low-magnification image of a horizontal section of a pituitary gland stained with the Periodic Acid-Schiff (PAS) technique. The pituitary is made up of two parts of very different origin: anterior pituitary or adenohypophysis (in which pars distalis, pars intermedia and pars tuberalis are distinguished), and neurohypophysis (comprising pars nervosa , infundibular stalk, and median eminence). Both pars distalis (D) and pars nervosa (N) are clearly seen in the figure. Between both, a thin pars intermedia (blue arrow) hardly stands out. (Red arrow: connective tissue capsule, very thin).
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Pituitary gland. PAS (2). Human. 20x. Image of the pars distalis, stained with the periodic acid-Schiff technique. Some cells are PAS-positive (arrowheads), which correspond to the basophil cells detected with hematoxylin-eosin. TSH cells, FSH / LH cells and ACTH cells would therefore be PAS-positive, whereas GH cells and PRL cells would be PAS-negative. The first three secrete glycoprotein hormones, and the last two, protein hormones. (Arrows: "fenestrated sinusoids").
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Pituitary gland. PAS (3). Human. 20x. With the periodic acid-Schiff technique, some cells (blue arrowheads) of the pars distalis show intense PAS-positivity. They correspond to the basophil cells detected with hematoxylin-eosin. TSH cells, FSH / LH cells and ACTH cells would therefore be PAS-positive, whereas GH cells and PRL cells would be PAS-negative. Some cells (red arrowhead) in which the cytoplasm does not stain at all would be classified as chromophobe cells. (Arrows: "fenestrated sinusoids").
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Pituitary gland. Gomori (1). Human. Horizontal, slightly oblique section of a pituitary stained with the Gomori technique. The more voluminous pars distalis (D) is seen at the bottom. Above and to the right a portion of pars tuberalis (T) is visible, in which the cross sections of venules (arrowhead) of the hypothalamic-pituitary portal system stand out. In the upper part of the image, a small portion of the infundibular stem (asterisk) can be seen. (Arrow: conjunctive capsule).
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Pituitary gland. Gomori (2). Human. 10x. Image of the pars distalis, stained with the Gomori technique. In the endocrine cell cords, two cell types are distinguished: acidophil cells (stained red by floxin), and basophil cells (stained blue by Gomori chromic hematoxylin). (Arrows: "fenestrated sinusoids").
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Pituitary gland. Gomori (3). Human. 10x. The endocrine cell cords of the pars distalis possess both cells stained red by phloxin (acidophil cells) (blue arrowheads), and cells stained blue by Gomori chromic hematoxylin (basophil cells) (red arrowheads). The cytoplasm of some cells does not appear to have been stained at all: these would be chromophobe cells, a clearly minority population. (S: "fenestrated sinusoids", filled with red blood cells).
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Pituitary gland. Gomori (4). Human. 4x. Horizontal, slightly oblique section of a pituitary. On the left, the pars distalis (D) is observed, with endocrine cell cords in which both acidophil and basophil cells appear. The center of the image corresponds to the pars tuberalis (T), in which there are abundant cross sections of venules (arrows) of the hypothalamic-pituitary portal system, as well as endocrine cell cords consisting of basophilic cells (stained blue by hematoxylin Gomori Chromic). In the lower part of the image, a small portion of the infundibular stem (asterisk) can be seen, with its typical appearance of nervous tissue and its low staining.
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Pituitary gland. Gomori (5). Human. 10x. In the pars tuberalis, the presence of numerous cross sections of venules (arrows) of the hypothalamic-pituitary portal system stands out, as well as endocrine cell cords consisting only of basophilic cells (stained blue by Gomori's chromic hematoxylin). Most of these basophilic cells express immunopositivity to FSH / LH hormones.
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Pituitary gland. Gabe (1). 4x. Low magnification image of a horizontal section of a pituitary gland from an experimental animal (rat). The pars distalis (D), the pars intermedia (I) and the pars nervosa (N) are perfectly differentiated.
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Pituitary gland. Gabe (2). 10x. With the Gabe technique, the TSH cells of the pars distalis (D) and the accumulations of neurosecretory material (Herring bodies) of the pars nervosa (N) are stained purple with aldehyde-thionine. In addition, orange G stains the pars distalis GH cells yellow-orange. (I: pars intermedia).
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Pituitary gland. Gabe (3). 20x. Image of the pars distalis of a rat pituitary in which aldehyde-thionine stained TSH cells (red arrowheads) in purple blue. GH cells (blue arrowheads) appear yellow-orange with orange G. (Arrow: “fenestrated sinusoid).
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Pituitary gland. Gabe (4). 40x. Pars distalis of a rat pituitary stained with the Gabe technique. TSH cells (red arrowheads) appear stained purple blue with aldehyde-thionine. GH cells (blue arrowheads) have been stained orange-yellow with orange G. The "fenestrated sinusoids" (arrows) are very notable, both for their large caliber and for the presence of bright yellow stained red blood cells.
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Pituitary gland. Gabe (5). 20x. In pars nervosa, with the Gabe technique, the neurosecretory material is revealed, since it stains purple blue with aldehyde-thionine. It appears both in the form of tiny dots and much larger globular structures, the Herring's bodies (red arrowheads). In the lower part of the image appears the pars intermedia (I). (Arrow: blood vessels filled with red blood cells).
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Pituitary gland. Gabe (6). 40x. The neurosecretory material can easily become apparent in pars nervosa, as it stains purple blue with aldehyde-thionine. It appears both in the form of tiny dots and much larger globular structures, the Herring's bodies (red arrowheads), which correspond to axonal dilatations that have a large number of neurosecretory granules. In the lower right part of the image a small portion of pars intermedia (I) is observed. (Arrow: blood vessels filled with red blood cells).
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Thyroid gland. HE (1). Human. 4x. The thyroid is an endocrine gland of the "follicular" histological type. It is made up of spherical formations of various sizes, the "thyroid follicles", immersed in a connective tissue stroma with abundant blood and lymphatic vessels. Each follicle is a hollow sphere, lined by a simple cuboidal epithelium, and filled with an eosinophilic and amorphous material, the so-called thyroid colloid. There is a basement membrane, not visible with hematoxylin-eosin, that completely surrounds each of the follicles.
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Thyroid gland. HE (2). Human. 10x. Thyroid follicles (F), in the human species, are of very different sizes. Each follicle is a hollow sphere, lined by a simple cuboidal epithelium made up of thyrocytes (arrowheads), filled with an eosinophilic and amorphous material, the so-called thyroid colloid (asterisk). This colloid appears more or less cracked and always retracted, so that there is an empty artificial space (arrow) between the colloid and the thyrocytes. (V: blood vessels, with red blood cells. VL: lymphatic vessels, artifactually dilated).
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Thyroid gland. HE (3). Human. 20x. Thyroid follicles, of different sizes, embedded in a connective tissue stroma, showing both thyrocytes (blue arrowhead) and thyroid colloid (asterisk), eosinophilic and amorphous. This colloid appears more or less cracked and retracted, leaving an empty artificial space (arrow) between the colloid and the thyrocytes. On the surface of the colloid it is common to observe small depressions, the so-called "reabsorption lacunae" (red arrowheads), which are considered an artifact. (V: blood vessels, with red blood cells. VL: lymphatic vessels, artifactually dilated).
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Thyroid gland. HE (4). Human. 40x. High magnification image of various thyroid follicles showing thyroid cells (blue arrowheads) and colloid (asterisk), retracted and cracked. In some areas, surrounding the follicle externally, appear a fine and homogeneous eosinophilic line, which corresponds to the basement membrane (red arrowheads).
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Thyroid gland. HE (5). Human. 40x. Thyroid follicles seen at high magnification, in which, apart from the thyrocytes (arrows), some cells located outside them can be seen, which belong to the follicle but do not contact with the follicular lumen; they correspond to C or parafollicular cells (blue arrowheads). (Red arrowheads: reabsorption lacunae).
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Thyroid gland. PAS (1). Human. 4x. Low magnification image of a human thyroid (the same as in the previous sample), stained with the PAS (periodic acid-Schiff) technique. The main interest of applying this technique is to show the PAS-positivity of the colloid, since it contains thyroglobulin, an iodinated glycoprotein.
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Thyroid gland. PAS (2). Human. 10x. Thyroid follicles showing the intense PAS positivity of the colloid, which maintains its homogeneous appearance and its cracked appearance. (VL: lymphatic vessels, artifactually dilated).
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Thyroid gland. PAS (3). Human. 20x. Thyroid follicles, with their thyrocytes (red arrowheads) and the thyroid colloid, retracted, cracked, and sometimes detached, showing marked PAS-positivity. (Blue arrowheads: reabsorption lacunae of the colloid. VL: lymphatic vessels, artifactually dilated).
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Parathyroid gland. HE (1). Human. Low magnification image of a parathyroid gland from a human adult. The stroma consists of a fine conjunctive capsule, barely noticeable, and by vascular-connective septa in which unilocular adipocytes (asterisk) are very abundant. The parenchyma is made up of cords and groups of glandular epithelial cells. There are two types of these cells: the chief cells (red arrow), and the oxyphil cells (blue arrow). The latter are non-secreting cells, have a tendency to appear in rounded, nodular-looking aggregates, and are absent before puberty. (Arrowheads: blood vessels).
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Parathyroid gland. HE (2). Human. 10x. Image of a parathyroid gland showing the arrangement, in nests and cords, of parenchymal cells. While the chief cells (red arrow) are homogeneously distributed, the oxyphil cells (blue arrow) show a tendency to group together and form rounded clusters with a nodular appearance. (Arrowheads: blood vessels. A: unilocular adipocytes).
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Parathyroid gland. HE (3). Human. 20x. The parenchymal cells of the parathyroid gland are arranged in nests and cords separated by connective septa. At this magnification, the main cells (red arrow) are perfectly differentiated from the oxyphilic cells (blue arrows). The latter stand out for their larger size, eosinophilic cytoplasm, and somewhat smaller and heterochromatic nucleus. (Arrowheads: blood vessels. A: unilocular adipocytes).
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Parathyroid gland. HE (4). Human. 20x. Large cluster (asterisk) of oxyphil cells, nodular in appearance, located in the upper left of the image. Oxyphil cells are larger than the chief ones, and have a small, heterochromatic nucleus, as well as a highly eosinophilic cytoplasm. Also striking is the fact that the boundaries between adjoining oxyphilic cells appear very sharp. The chief cells (arrow) are smaller, the cytoplasm is paler, and its nucleus is larger and more euchromatic than that of oxyphil cells. (Arrowheads: blood vessels. A: unilocular adipocytes).
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Parathyroid gland. HE (5). Human. 40x. In this image, practically all of the cells that are observed are chief cells, arranged in thin cords separated by connective septa. Note how the nucleus of these cells is relatively euchromatic and large in relation to cell volume. The cytoplasm stains moderately. (Arrowheads: blood vessels. A: unilocular adipocytes).
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Parathyroid gland. HE (6). Human. 40x. In this image, on the contrary, the oxyphilic cells are the predominant element, forming, in the right half of the image, a large cluster. Note the typical appearance of oxyphilic cells: larger than the chief ones, they have a small heterochromatic nucleus, as well as a highly eosinophilic cytoplasm. Furthermore, the boundaries between contiguous oxyphilic cells appear very evident. In some chief cells the cytoplasm has small granulations (arrowheads). (V: blood vessels. A: unilocular adipocytes).
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Infantile parathyroid gland. HE (1). Human. Low magnification image showing two parathyroid glands (P) of a child. Both are embedded in white or yellow fatty tissue. The basophilic structure that appears next to the gland on the right is the thymus (T). This is explained because both the inferior parathyroids and the thymus derive embryologically from the third branchial pouch.
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Infantile parathyroid gland. HE (2). Human. 4x. In the parathyroid gland (P) of the child, the only presence of chief cells is striking. Oxyphil cells, on the contrary, do not exist, since they begin to appear after puberty. However, some adipocytes (arrowheads) can be seen in the connective tissue stroma of the gland. (T: thymus).
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Infantile parathyroid gland. HE (3). Human. 10x. In the child's parathyroid gland there is a single parenchymal cell type, the chief cells, of a very clear cytoplasm, arranged in cords and large groups, separated by connective tissue septa in which some unilocular adipocytes can be seen (a). There are no oxyphil cells. (Arrows: blood vessels).
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Infantile parathyroid gland. HE (4). Human. 20x. The only parenchymal cell type of the child's parathyroid gland is the chief cell: it has a very clear cytoplasm, virtually not stained, and a rounded relatively heterochromatic nucleus. There are no oxyphil cells before puberty. Very occasionally, in the parathyroid, follicular-looking structures (f) may appear, occupied by a slightly eosinophilic lumpy material. (Arrows: blood vessels with red blood cells. A: unilocular adipocytes).
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Infantile parathyroid gland. HE (5). Human. 40x. Nests and chief cell cords in a child's parathyroid gland. These cells have a round nucleus, rather heterochromatic, and an extremely pale cytoplasm. Note how the nuclei of the chief cells located in the immediate vicinity of the conjunctive capsule (asterisk) that surrounds the organ, tend to be oriented forming a row next to the basement membrane (arrowheads) which, at this increase, appears as a thin eosinophilic line. (Arrows: blood capillaries within the connective tissue septa).
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Adrenal gland. HE (1). Low-magnification image of a dog's adrenal gland. Its two parts are easily observed: cortex (C) and medulla (M). (Asterisk: bleeding area within the connective tissue capsule. Arrow: nerves).
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Adrenal gland. HE (2). 2x. The adrenal gland has two perfectly differentiated parts: the cortex (C) (which in turn consists of three zones: glomerulosa (g), fasciculata (f) and reticularis (r)) and the medulla (M). On the outside, the gland is enveloped by a fine connective tissue capsule (arrow). (Asterisk: blood vessel, with a wide lumen, in the adrenal medulla).
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Adrenal gland. HE (3). 10x. Cortex of the adrenal gland in which its three regions are observed: from left to right, the zona glomerulosa (g), the zona fasciculata (f) and the zona reticularis (r). The zona glomerulosa is made up of large nests or groups of cells that are arranged forming rounded or elongated structures. Parallel radial cords of pale-looking cells stand out in the zona fasciculata. Finally, the zona reticularis has highly disorganized cords of eosinophilic cytoplasm cells. On the left, a narrow strip of the conjunctive capsule (asterisk) that surrounds the organ is observed. (Arrowheads: wide-span blood capillaries within connective tissue septa).
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Adrenal gland. HE (4). 20x. The center of the image is occupied by the zona glomerulosa (g), made up of large nests or groups of cells that are arranged in rounded or elongated masses. More deeply, (red asterisk), the typical parallel cell cords of the zona fasciculata (f) already appear, among which blood capillaries are seen (arrows ) of very wide lumen (“fenestrated sinusoids”). In the upper part of the image, the connective tissue capsule (blue asterisk) that surrounds the organ is seen, from which fine connective tissue partitions (blue arrowheads) emerge, separating the cell nests from the glomerular layer.
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Adrenal gland. HE (5). 20x. Zona fasciculata of the adrenal gland cortex, with its typical arrangement in cell cords (arrows) parallel to each other, of variable thickness, and separated from each other by wide blood capillaries (arrowheads), which can be classified as "fenestrated sinusoids ”. The endocrine cells that make up this zona fasciculata have a cytoplasm little stained, since it contains numerous lipid droplets.
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Adrenal gland. HE (6). 40x. High-magnification image of the zona glomerulosa of the adrenal cortex. It is made up of large nests or groups of cells that are arranged in rounded or elongated masses. These cellular nests are separated by fine connective tissue septa (arrows) that start from the connective tissue capsule (asterisk) that surrounds the organ. Frecuently, the endocrine cells of this layer also show lipid droplets (arrowheads), which gives them a pale staining.
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Adrenal gland. HE (7). 40x. Zona fasciculata of the adrenal gland cortex. It has a characteristic arrangement in cell cords (arrows) more or less parallel to each other, of variable thickness, separated from each other by wide blood capillaries (arrowheads) ("fenestrated sinusoids"). The endocrine cells that make up this zona fasciculata, as can be seen above all in the lower half of the image, have a poorly stained cytoplasm due to the presence of abundant lipid droplets.
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Adrenal gland. HE (8). 40x. The deepest portion of the adrenal gland cortex is the zona reticularis. As can be seen from this high-magnification image, endocrine cells possess eosinophilic cytoplasm with few lipid droplets, and organize themselves in irregularly arranged cell cords. The adrenal medulla (asterisk) is already visible in the lower right corner. (Arrowheads: wide blood capillaries located in connective tissue septa).
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Adrenal gland. HE (9). 40x. Limit between the zona reticularis of the adrenal cortex (top, right) (r) and the adrenal medulla (bottom, left) (M) of the gland. The endocrine cells of the medulla have a rather euchromatic nucleus and a slightly basophilic cytoplasm, and they cluster together forming large nests separated by fine connective tissue septa (arrowheads). Note the evident contrast with the eosinophilia of the cytoplasm of the cells of the zona reticularis.
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Adrenal gland. HE (10). 40x. High-magnification image of the adrenal medulla. Medullary endocrine cells clump together into large nests separated by fine -connective tissue septa (arrowheads). These cells have a rather euchromatic nucleus and a slightly basophilic cytoplasm, which frequently appears with signs of poor conservation, even when fixation has been carried out quickly. (A: arteriole).
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Adrenal gland. HE (1). Human. Low magnification image of an adrenal gland, in which its two parts are easily observed: cortex (C) and medulla (M).
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Adrenal gland. HE (2). Human. 10x. At low magnification, the three zones of the adrenal cortex (C) are seen: glomerulosa (g), fasciculata (f) and reticularis (r). The medulla (M) is located internally, and stands out for its more basophilia. On the outside, there is a fine connective tissue capsule (arrow) that completely surrounds the organ.
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Adrenal gland. HE (3). Human. 10x. Two superficial thirds of the adrenal gland cortex observed at medium magnification. The most externally located region, of narrow thickness, is the zona glomerulosa (g), in which the cells are arranged forming groups or nests of rounded shape. Underneath is the zona fasciculata (f), whose cells (paler due to the presence of lipid droplets in their cytoplasm) tend to orient themselves forming parallel cords with each other. Both the glomerulosa and fasciculata zones show fine connective tissue septa (arrowheads). (Asterisk: connective tissue capsule).
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Adrenal gland. HE (4). Human. 20x. In the zona glomerulosa (g) of the adrenal cortex, the cells (with few lipid droplets and moderately eosinophilic cytoplasm) are arranged forming groups or nests of rounded shape. The cells of the zona fasciculata (f), on the other hand, are paler due to the presence of extremely large lipid droplets in their cytoplasm, and tend to orient themselves constituting parallel cords to each other. (Arrowheads: connective tissue septa, some of which have red blood cells inside. Asterisk: connective tissue capsule. Red arrow: cell with a polyploid nucleus. Blue arrow: binucleated cell).
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Adrenal gland. HE (5). Human. 20x. Zona fasciculata of the adrenal gland cortex. Sometimes, the cells tend to become disordered, and the typical arrangement in parallel cords is less evident. Note the abundance of lipid droplets in the cytoplasm of these cells. (Arrowheads: vascular- connective tissue septa).
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Adrenal gland. HE (6). Human. 40x. Zona fasciculata of the adrenal gland cortex. Sometimes, the typical arrangement in parallel cords is less evident. The abundance of lipid droplets in the cytoplasm of these cells is striking, which gives them a foamy appearance and is the cause of their low staining. (Arrowheads: vascular- connective tissue septa).
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Adrenal gland. HE (7). Human. 20x. Deep part of the zona fasciculata (f), zona reticularis (r), and adrenal medulla (M) (right). The cells of the zona reticularis, which are arranged in apparent disorder, have a brownish pigment (lipofuscin) in the cytoplasm. In addition, the amount of lipid droplets that these cells accumulate is less than those in the zona fasciculata cells. In the adrenal medulla, endocrine cells show a rather euchromatic nucleus and a slightly basophilic cytoplasm. They are grouped together forming large cellular nests separated by fine connective tissue septa. (Asterisk: islet of cortical cells apparently isolated inside the medulla. This would be a sectional plane effect, since the cortico-medullar limit is not totally rectilinear).
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Adrenal gland. HE (8). Human. 40x. Zona reticularis of the adrenal cortex seen at high magnification. Endocrine cells are arranged in irregularly distributed cords, separated by connective tissue septa in which the blood capillaries (arrows) stand out for their wide lumen ("fenestrated sinusoids"). Cells in this layer have few lipid droplets, and the presence of varying amounts of a brownish pigment (lipofuscin) (arrowheads) is typically in their cytoplasms.
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Adrenal gland. HE (9). Human. 20x. Medium magnification image of the adrenal medulla (M), flanked on the right and left by the cortex (C). Medullary endocrine cells clump together into large nests separated by fine connective tissue septa (arrowheads). These cells have a relatively euchromatic nucleus and a basophilic cytoplasm. Some cells appear to show signs of poor conservation.
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Adrenal gland (Medulla). HE (1). Low magnification image of a rabbit's adrenal gland, showing its two parts: cortex (C) (with several distinguishable layers) and medulla (M).
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Adrenal gland (Medulla). HE (2). 10x. Image of the outermost two-thirds of the cortex of a rabbit adrenal gland showing the glomerulosa (g) and the fasciculata (f) zones. The zona glomerulosa is made up of groupings of cells that are arranged into rounded, elongated or horseshoe-shaped structures. Parallel cords of pale-looking cytoplasm cells stand out in the zona fasciculata. In the upper part, a thin connective tissue capsule (arrow) is seen surrounding the gland.
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Adrenal gland (Medulla). HE (3). 10x. Cortico-medullar limit in the rabbit adrenal gland. The medulla (M) (right) is perfectly differentiated from the cortex (C) (left) by the basophilia of its cells and by their arrangement, in large nests separated by connective tissue septa. Note the irregularity of the border between the cortex and the medulla, which gives rise to the presence (by effect of the section plane) of both groups of medullary cells (blue arrow) in the deep cortex, and of cortex cells (red arrow) in the superficial medulla.
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Adrenal gland (Medulla). HE (4). 20x. The medulla (M) (right) is easily distinguished from the cortex (C) (left) by the basophilia of its cells and by their arrangement, in large nests separated by connective tissue septa (asterisks). Note the irregularity of the border between the cortex and the medulla, which gives rise to the presence (by effect of the section plane) of both groups of medullary cells (blue arrow) in the deep cortex, and of cortex cells (red arrow) in the superficial medulla.
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Adrenal gland (Medulla). HE (5). 20x. Superficial region of the medulla of the rabbit's adrenal gland. In the image, the medullary cells (red arrows) (of variable basophilic cytoplasm) are mixed with small groups of cells (blue arrows) belonging to the cortex (they have slightly eosinophilic or pale cytoplasm, due to the presence of lipid droplets). (Asterisks: very wide lumen blood vessels within the connective tissue septa).
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Adrenal gland (Medulla). HE (6). 40x. Medulla of the rabbit's adrenal gland. The medullary cells (red asterisk) have a basophilic cytoplasm, and often have an elongated shape, arranging themselves "in a palisade" surrounding blood vessels (V) of a wide lumen and thin wall. There are also some groups of cortical cells (blue asterisk), characterized by presenting a slightly eosinophilia and abundant lipid droplets.
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Islets of Langerhans (endocrine pancreas). HE (1). Human. Low magnification of a section of the pancreas in which abundant small, pale, rounded structures are irregularly distributed within this exocrine gland. They are the islets of Langerhans (arrowheads), an endocrine component of the pancreas.
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Islets of Langerhans (endocrine pancreas). HE (2). Human. 10x. The islets of Langerhans (I) are seen as rounded structures, paler than the tubulo-acini (T) of the exocrine part of the gland. In histological sections, they appear with variable sizes, depending on the section plane. (Arrows: excretory ducts of the exocrine pancreas, with the lumen occupied by secretion).
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Islets of Langerhans (endocrine pancreas). HE (3). Human. 20x. Islet of Langerhans (I) surrounded by serous tubule-acini (T). Its cells, considerably paler than those of the tubulo-acini, are arranged forming cords and nests separated by connective tissue septa (arrowheads). Therefore, the islets of Langerhans can be said to have the histological appearance of an endocrine gland of the solid, cordonal type.
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Islets of Langerhans (endocrine pancreas). HE (4). Human. 40x. High magnification image of an islet of Langerhans. Its cells, paler than those that make up the exocrine serous tubule-acini (T), are arranged in nests and cords separated by connective tissue septa (asterisk). With hematoxylin-eosin it is very difficult to distinguish endocrine cell types (A or alpha, B or beta, D or delta, ...) on the islet. Some peripheral cells with a certain eosinophilia would correspond to A or alpha cells (arrowhead). Most of the rest of the cells would be B or beta cells.
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Islets of Langerhans (endocrine pancreas). HE (5). Human. 40x. High magnification image of an islet of Langerhans. Its endocrine cells are paler than those of the serous tubuloacini (T) of the exocrine pancreas, and they are arranged in nests and cords separated by conjunctive septa. With conventional histological techniques, such as hematoxylin-eosin, it is very difficult to distinguish endocrine cell types (A or alpha, B or beta, D or delta, ...) in the islet. Some cells with some eosinophilia, located peripherally, correspond to A or alpha cells (arrow). Most of the rest of the cells would be B or beta cells.
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Pineal gland. HE (1). Human. Low magnification image of a sagittal sectioned pineal gland. Anatomically it is related to the habenular commissure (H) (where there are numerous calcifications) and to the posterior commissure (P). The gland is covered by a connective tissue capsule (C) from which septa (arrowhead) enter towards the interior of the pineal, and branch out to delimit small irregular lobules (L). It is characteristic of the pineal gland to find calcifications (arrows) that are very basophilic, of varied sizes and often with an irregular contour. Glial scar (G) and small cystic cavities (Q) are also observed.
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Pineal gland. HE (2). Human. 4x. Organization of the parenchyma of the pineal gland, formed by pinealocytes, in small lobules (L) delimited by branched connective tissue septa (asterisk).
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Pineal gland. HE (3). Human. 10x. Pinealocytes are irregularly grouped inside lobules (L), separated by connective septa (C) that branch inside the gland.
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Pineal gland. HE (4). Human. 10x. Glial scars (G), formed by astrocytes, can be found in the pineal gland. They present a fibrillar appearance, due to the grouping of astrocytic processes, with a low density of nuclei. Immersed in the pineal parenchyma, there are calcified concretions (acervuli) (arrows), very basophilic, of very varied size. They frequently break as a consequence of the histological technique.
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Pineal gland. HE (5). Human. 4x. Glial scar (G) of the pineal gland. It has a clear, fibrillar appearance, with low nuclear density, and has an irregular contour, where glial extensions intermingle with pinealocytes. Inside the scar, some small calcified concretion (acervuli) (arrowhead) can be seen. Around the scar, in the pineal parenchyma, there are numerous acervuli, many of which have an irregular contour acquiring a morular appearance (arrows).
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Pineal gland. HE (6). Human. 10x. High magnification of the glial scar (G) in the previous image. It has a low density of nuclei, corresponding to astrocytes, and among them fibrillar structures are observed. Small calcifications (arrowhead) can be observed in the scar, which contrast with the large size of that calcifications (arrows) located in the pineal parenchyma.
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Pineal gland. PTAH (1). Human. Low magnification image showing a pineal gland stained with the phosphotungstic acid hematoxylin technique, which highlights the glial scars by staining in blue the astrocyte processes. Two glial scars (G) are shown in the image, one of them being surrounded by numerous calcified concretions (C). The rest of the image corresponds to the pineal parenchyma (P), where some branched connective septa are seen (arrow).
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Pineal gland. PTAH (2). Human. 10x. The glial scar (G) stands out with this technique, that stains in bluish colour the astrocyte processes. Interspersed with the extensions, the nuclei of the astrocytes are identified. From the margins of the scar, extensions arise (arrow) that penetrate the parenchyma and mix with the pinealocytes. In the vicinity of the glial scar are numerous calcified concretions (acervuli) (C) of irregular contour.
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Pineal gland. PTAH (3). Human. 20x. High magnification showing the boundary between the glial scar (G) and the pineal parenchyma (P). The scar is made up of numerous astrocytic processes that form a compact network, where the nuclei of the astrocytes are found. In the border area of the scar, astrocytic processes (arrows) arise invading the pineal parenchyma and intermingle with pinealocytes.
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