Arterial supply and venous drainage of the choroid plexus of the human lateral ventricle in the prenatal period as revealed by vascular corrosion casts and SEM.

The topography of the arterial supply and venous drainage was visualised by corrosion casting and scanning electron microscopy in the human foetal (20 weeks) choroid plexus of the lateral ventricle. Although secondary villi were not yet present at that developmental stage, the topography of the large arteries and veins almost fully corresponded to that described in adult individuals. The only major difference observed was a lack of the typical tortuosity of the lateral branch of the anterior choroidal artery and of the superior choroidal vein, which probably develops during further expansion of the vascular system associated with the formation of secondary villi.

The microvascular architecture of the choroid plexus in fetal human brain lateral ventricle: a scanning electron microscopy study of corrosion casts.

The microvascular architecture of developing lateral ventricle choroid plexus was investigated by corrosion casting and scanning electron microscopy in human fetuses aged 20 gestational weeks. The areas with different microvascular patterns corresponded to the particular parts of the mature plexus: anterior part, glomus, posterior part, the villous fringe and the free margin. In the posterior part, densely packed parallel arterioles and venules were surrounded by sheath-like capillary networks. Other areas contained compact capillary plexuses of the primary villi: the most prominent, protruding basket- and leaf-shaped plexuses were observed in the villous fringe, whilst less numerous and smaller plexuses occurred in the anterior part and glomus. The capillaries of the plexuses had a large diameter and sinusoidal dilations, and showed the presence of occasional short, blind sprouts indicative of angiogenesis. Short anastomoses between arterioles supplying the plexuses and venules draining them were only rarely observed. In the upper area of the choroid plexus, the superior choroidal vein was surrounded by a capillary network forming small, glomerular or rosette-shapes plexuses. The free margin of the choroid plexus was characterized by flat, multiple, arcade-like capillary loops. The general vascular architecture of the human choroid plexus at 20 gestational weeks seems to be similar to that of postnatal/mature plexus, still lacking, however, the complex vascular plexuses of the secondary villi.

The structure of acquired aural cholesteatoma as revealed by scanning electron microscopy.

The structural features of cells, their surfaces and the extracellular matrix were investigated in acquired aural cholesteatoma. Cholesteatomas surgically removed from 30 patients were examined by a scanning electron microscope (SEM). The predominant part of a cholesteatoma was composed of stratified squamous epithelium, showing extensive chaotic desquamation. The surface sculpture of the keratinocytes and corneocytes varied from parallel ridges, irregular microplicae and mirovilli, to flat grooves and pits and a completely smooth surface. Sheetlike lamellar structures, probably representing an intercellular lipid-forming permeability barrier, were also observed. Small crystals located in the perimatrix were observed in one case. According to the SEM observations, cholesteatoma epithelium is characterised by abnormal and uncoordinated keratinisation, with a predominance of the advanced stages of the process.

Surface structures of aural polyps: a scanning electron microscopic study.

Surfaces of aural polyps collected from 30 patients were examined by scanning electron microscopy. In the polyps not associated with cholesteatoma, the epithelial lining showed individually variable metaplasia towards cuboidal 'cobblestone'-type and squamous epithelium covered with microvilli of various shapes and sizes. Squamous epithelium was present on the surface of all polyps with underlying cholesteatoma, with superficial cells possessing elongated microvilli, microplicae of different sizes, grooves and pits. Such surface structures reflect different stages of the keratinization process that seems to be characteristic for the epithelial lining of polyps with underlying cholesteatoma. Incomplete epithelium accompanied by granulation tissue was found in several polyps; in two cholesteatoma-associated polyps plate-like cholesterol crystals were observed.

Vascular architecture of normal human urinary bladder and its remodeling in cancer, as revealed by corrosion casting.

The vasculature of normal human urinary bladder wall and its tumors were studied using corrosion casting and scanning electron microscopy. In the normal wall, a regular organization of highly tortuous horizontal and vertical vessels allows accommodation of the vascular system to spatial changes resulting from the filling/voiding cycle. The vasculature of tumors is a result of remodeling of preexisting wall vessels associated with gradual growth of the neoplastic tissue. The shape and arrangement of blood vessels in different regions of the tumor seem to reflect a variable dynamics of tumor development and possible influence of various angiogenesis-promoting growth factors.

Vascular system of the human spinal cord in the prenatal period: a dye injection and corrosion casting study.

The vascularization of the spinal cord was investigated in 50 human fetuses aged from 10 to 28 gestational weeks using dye injection methods and corrosion casting accompanied by scanning electron microscopy. In the investigated period of fetal development, the general vascular architecture of the spinal cord, corresponding to that described postnatally, seemed to be already established. The observed changes included: (1) remodeling of the supplying (extrinsic) arterial branches, (2) transformation of the posterior anastomotic chain into two distinct posterior spinal arteries, and (3) development of the capillary networks in the gray and white matter. The remodeling of the radicular arteries supplying the spinal cord was accompanied by a decrease in their number and transition from regular to irregular distribution (appearance of intersegmental differences in their frequency). The anterior spinal artery and regular array of the central arteries were already present in the youngest fetuses examined, but the final remodeling of the posterior anastomotic chain into two posterior spinal arteries occurred between 15th and 20th week of fetal life indicating that the vascularization of the anterior region of the spinal cord in the investigated period of fetal life was more advanced as compared with that of the posterior region. The capillary network of the gray matter in the youngest fetuses had the form of discrete glomerular plexuses supplied by groups of central arteries and mainly vascularizing the anterior horns. Successively, the plexuses fused to form a continuous system along the anterior columns and the system expanded to fully vascularize the posterior horns. The white matter in the earlier fetal period seemed to be partially avascular, later the density of capillaries vascularizing those areas was still much lower than in the gray matter. The veins showed considerably greater variability than the arteries, as far as their topography and distribution was concerned. High tortuosity characterized the superficial veins, especially in the younger fetuses, although the degree of tortuosity differed even between individual fetuses. Only anterior spinal and central arteries were usually accompanied by their venous counterparts, the other veins seemed to have no regular topographical relations with the arteries.

Architecture of blood vessels in human fetal gastric corpus: a corrosion casting study.

Vascular architecture of the gastric corpus was investigated in 16-24 wk human fetuses using a corrosion casting technique and the scanning electron microscopy. The general distribution of blood vessels seen in adults has already been established in the fetus, with three major vascular plexuses located in the serosa, submucosa and mucosa. The serosal plexus, supplied and drained by large extramural vessels, contained anastomosing, arcade-like arrays of arteries and veins with their branches piercing the muscularis and communicating with the compact submucosal plexus. Vertical arterioles and capillaries were sent by submucosal arteries to supply a very dense capillary plexus which surrounded the gastric pits and consisted of wide, sinusoidal vessels showing morphological manifestations of angiogenesis by intussusceptive growth. The plexus was drained by vertical venules emptying into submucosal veins. In contrast to the richly vascularized upper half of the mucosa, the lower half showed a relative paucity of blood vessels, probably due to the thinness of the fetal mucosa allowing an effective diffusion of oxygen and nutrients from the upper half. Neither arteriovenous anastomoses, nor end-arteries were found in the fetal stomach. Results of this study support one of the two existing models of mucosal vascularization in the human stomach: i.e. the model postulating the presence of short and long arterioles and two distinct, albeit interconnected capillary networks in the upper and lower zones of the mucosa respectively. In human fetuses, the latter network is absent; it probably develops by remodelling of the preexisting vertical capillaries in the last phase of pregnancy, prior to the onset of gastric gland function.

Microvascular architecture of the human urinary bladder wall: a corrosion casting study.

The vascular system of the urinary bladder wall effectively performs its function in spite of considerable spatial changes due to the filling/voiding cycle. However, only a few studies have dealt with the microvascular architecture of the bladder wall and only two, using old-fashioned techniques, were devoted to the human bladder. This study presents the microvasculature of the human bladder wall visualized by scanning electron microscopy of vascular corrosion casts. Postoperative bladder specimens obtained from patients with advanced bladder tumors were filled with small amount (80 ml) of saline and perfused via at least four largest arteries with anticoagulant-containing saline followed by paraformaldehyde/glutaraldehyde fixative and Mercox resin. After polymerization of the resin, the vascular casts were macerated with potassium hydroxide, cleaned with formic acid and water and freeze dried. Only regions of the bladder wall distant to the tumor were examined in light and scanning electron microscopes. The almost empty state of the bladder was manifested by extensive folding of the mucosa and tortuosity of almost all vessels other than capillaries. The branches of main arteries and veins formed an adventitial/serosal plexus which directly supplied/drained the capillary network of the muscularis and sent long perpendicular vessels to the mucosal plexus. These vessels had straight or coiled course depending on whether they terminated at the top or at the base of the mucosal folds. The rich mucosal plexus followed the folds parallel to their surface and gave off short, straight, mostly perpendicular twigs communicating with the subepithelial capillary network. Apart from very few vascular interconnections between the mucosal plexus and the muscularis, the submucosa was generally avascular. The subepithelial capillary network showed extreme density and uneven contours of the capillaries, only in less folded areas of trigone and urethral orifice the network was looser and capillaries thinner. The capillary system of the muscularis was poorly developed. Due to its architecture, tortuosity, and coiling/uncoiling capabilities, the microvasculature of the human urinary bladder wall seems to efficiently accommodate changes associated with cyclic contraction and stretching. Disturbances in blood flow induced by overdistension of the bladder reported in several studies may be due to pressure of the urine affecting the patency of the vessels rather than to the spatial insufficiency of the vascular system.

Vascular architecture of human urinary bladder carcinoma: a SEM study of corrosion casts.

The vascular architecture of five advanced invasive papillary tumours of the urinary bladder was investigated using corrosion casting and scanning electron microscopy. The superficial vasculature was composed predominantly of capillary systems of two types: dense flat networks with numerous interconnections and tightly packed tortuous loops, forming multiple irregular folds that reflected the papillary morphology of the tumours. The capillaries were supplied and drained by numerous straight nonanastomosing arterioles and venules, which arose by way of multiple branching of larger vessels originating from the mucosal plexus of the bladder. Differences between the tumours in the spatial arrangement of these vessels probably reflect different growth dynamics. The intramural parts of the tumours contained a chaotic network of straight, uniform capillaries with numerous sprouts, which was very different from the superficial capillary system. It is postulated that different angiogenesis-targeted growth factors may be expressed in the phases of exophytic growth and muscularis invasion of the tumour, leading to the formation of different microvascular patterns.

Microcirculation of human fetal posterior root ganglia: a scanning electron microscopic study of corrosion casts.

The vasculature of lumbar posterior root ganglia was investigated in human fetuses aged 17-24 weeks; using the corrosion casting technique and scanning electron microscopy. The arterial supply consisted of one main artery and occasional arterioles entering the ganglion at its pole and running axially, while the venous drainage was located at the periphery of the ganglion, thus indicating a centrifugal pattern of blood flow. The dense capillary network of the ganglion showed the roughly parallel course of the vessels in the central zone and an irregular arrangement in the peripheral zone where capillaries formed "nests", probably surrounding individual perikaryons of ganglionic cells. The capillaries had a sinusoidal character with numerous dilatations about twice the normal capillary size, as well as occasional larger vascular spaces resulting from capillary interconnections and suggesting the intussusceptive type of angiogenesis.

The architecture of internal blood vessels in human fetal vertebral bodies.

The internal vascular system of vertebral bodies was investigated in 17-24 wk human fetuses by acrylic dye injection and by corrosion casting/scanning electron microscopy. The regions of intervertebral spaces did not contain blood vessels. The radial metaphyseal vessels were at the stage of centripetal ingrowth into the vertebral body cartilage and their terminal, blindly ending segments had a form of cuff-like capillary plexuses. The anterolateral equatorial arteries communicating with the vessels of the ossification centre were only rarely found. The centre was usually supplied by 2 posterior (nutrient) arteries which branched into an arcade-like array of arterioles equipped with occasional sphincters and giving origin to a dense network of peripherally located capillaries. Numerous blind capillary buds formed the advancing border of the ossification centre. The veins usually accompanied the arteries. In the ossification centre the venous compartment consisted of sinuses drained by larger posterior veins. In the 17 wk fetus, an axial avascular area was observed in the place of notochord localisation, indicating the formation of a ring-shaped ossification centre around the notochord remnants at earlier stages of fetal development.

Microvasculature of the human fetal laryngeal anterior commissure.

The vascular pattern of the injected with Mercox human fetal larynges, especially of the anterior commissure and surrounding it area, was analysed within the horizontal and frontal sections under a light microscope. The main result of our study was confirmation of existence of the avascular "plane zero" situated above the anterior commissure, which separates that structure from the supraglottic tier. That finding i.e. avascular separation between teh middle and upper laryngeal compartments, already present in the fetal period, has clinical implications as far as the spread of neoplastic process within the larynx is cancerued.

Vascular architecture of the human fetal adrenal gland: a SEM study of corrosion casts.

The vascular architecture of adrenal glands was investigated in human fetuses aged from 16 to 24 weeks, using microcorrosion casts and scanning electron microscopy. The fetal adrenals showed an arrangement of blood vessels remarkably similar to that described in adult glands. There was a clear centripetal pattern from superficial arteries and their branches, via irregular capillaries of the subcapsular plexus and definitive cortex, and then via the radial sinusoids and venous sinuses of the fetal cortex, to the central vein. Rare medullary arterioles traversed the cortex to break up into small local capillary networks in the central region of the gland. Some superficial capillaries were drained by occasional subcapsular veins. No portal system was observed in the fetal adrenals.

Season-specific thymic architecture in the frog, Rana temporaria: SEM studies.

It is already known that the thymus of the adult common frog, Rana temporaria, undergoes conspicuous annual cyclic changes. Light microscopic (LM) observations are at present confirmed by three-dimensional scanning electron microscopy (SEM) pictures showing the presence of a characteristic cortico-medullary division of summer thymuses and cystic appearance of winter organs. Summer thymuses are larger, much heavier and populated by a significantly higher number of cells than winter organs. The season-specific thymic size, cell content and distribution are reflected by its angioarchitecture. The microcorrosion casts of vascular system of winter thymuses are much smaller and more compact than those of the summer organs in which vessels are arranged at larger spatial intervals. It seems that thymic enlargement following the winter atrophy results from vernal repopulation of the thymic cortex by thymocytes which in consequence induces a reshaping of the existing capillary network.

Thymic vascular system of the European common frog, Rana temporaria: a scanning electron-microscopic study of vascular casts.

Vascular corrosion casts of the thymus of adult individuals of the European common frog, Rana temporaria, were analysed by scanning electron microscopy. The main arterial vessel, which is derived either from the temporal artery or from the auricular ramus, approaches the central territory of the gland and branches into "twigs" that, on penetrating the parenchyma, give rise to capillaries. Most of these capillaries run vertically towards the surface of the gland; they either join the superficial capillary plexus or follow this plexus for a variable distance and then run back towards the medulla, forming capillary loops. The former capillaries link with the extensive venous plexus composed of irregular meshes, whereas the latter capillaries join the venules at the cortico-medullary boundary and finally escape into collecting veins on the gland surface. The venous twigs, which join together near the gland, form the main thymic vein, which empties into the external jugular vein. The details of the thymic vasculature of the anuran amphibian, R. temporaria, are compared with those described in mammalian species, viz. the mouse, rat and guinea pig.

Corrosion casting study on the vasculature of nasal mucosa in the human fetus.

BACKGROUND: The vasculature of the nasal mucosa in the human fetus so far has not been investigated morphologically by modern techniques. METHODS: Nasal blood vessels were studied in 18-21-week-old human fetuses by corrosion casting and scanning electron microscopy. RESULTS: The general vascular architecture was similar to that described for adult humans, with (1) a dense network of subepithelial capillaries, (2) a mucosal layer of larger vessels, predominantly veins, and (3) large arteries located near the perichondrium. Specific vessel types characteristic of the nasal mucosa and important for its functions in adults, such as cavernous veins or cushion veins, were, however, absent in the fetuses, although probable precursor forms of cushion veins could be observed. The arteriovenous anastomoses had the form of short bridges, and no tortuous or glomerular anastomoses present in the mature nasal mucosa were found. CONCLUSIONS: The underdevelopment of some vascular areas is postulated to reflect the functional immaturity of the respiratory system in the fetus.

Microvasculature of the dorsal mucosa of human fetal tongue: a SEM study of corrosion casts.

The vasculature of the dorsal mucosa of the tongue was investigated in 18-21 week human fetuses by corrosion casting and scanning electron microscopy. Microvascular systems of the fungiform, foliate and circumvallate papillae, albeit less complex, showed similarity to those described in children, while the capillary networks of the filiform papillae were not yet fully developed, having either a knot-like or cone-like form instead of the corolla-like pattern typical of the postnatal period. Morphological features suggesting angiogenesis included both capillary outgrowths characteristic of vascular sprouting and tiny holes in the vascular walls regarded as evidence of intussusceptive capillary growth. The subpapillary vascular network supplying and draining the papillary vessels was composed of the more superficial capillary bed and the deeper plexus of larger arterioles and venules.

Microvascular corrosion casting in the study of tumor vascularity: a review.

Tumor blood flow is dependent on the structure and three-dimensional (3-D) architecture of the vascular network. The latter can be best studied by scanning electron microscopy of microvascular corrosion casts. However, literature reviews show that nearly all studies using this technique render comparisons of different tumors more difficult since they are mainly based on descriptive terms that might lead to misunderstandings. Qualitative comparisons of 13 experimental and 3 human primary tumors of different origin show a high degree of similarity in the vasculature. Quantitative analysis of these casts reveals similar ranges of parameters such as diameters, intervascular and interbranching distances. Diameters of vessels with capillary wall structure range from 6 micron m to 55 micron m in the human primary tumors (renal clear cell carcinoma, basalioma), and from 5 micron m to 80 micron m in xenografted tumors (sarcomas, colon carcinoma). Intervascular distances in the human primary tumors range from 2 micron m to 52 micron m, and from 11 micron m to 105 micron m in the xenografts. Interbranching distances range from 34 micron m to 258 micron m in the former, and from 11 micron m to 160 micron m in the latter. Both qualitative and quantitative analyses of tumor microvascular corrosion casts enable pathophysiological conclusions to be drawn and contribute to a better understanding of tumor vascularity.

The vascular architecture of human fetal oviduct: a scanning electron microscopic study of corrosion casts.

Vascular architecture was investigated, in 18-21 week old human fetuses, for the first time with the use of corrosion casting and scanning electron microscopy, which offer high resolution and three-dimensional images of the vascular networks. The general arrangement of large vessels was similar to that described for the mature oviduct; however, the intramural vasculature of the muscular layer and mucosal folds consisted predominantly of capillary and sinusoidal networks. A characteristic feature of the fetal oviduct was a prominent sub-serosal venous plexus, which was most extensive in the isthmic segment. The relatively low degree of differentiation found in the fetal oviduct vasculature seems to reflect its functional immaturity.