1,720,984 research outputs found
Morphology of epiphyseal apparatus of a ranid frog (Rana Esculenta)
No full textMorphological, histochemical and ultrastructural investigations on epiphyseal apparatus of Rana Esculenta were made. The most important findings were the following: 1) metaphyseal cartilage is localized inside proximal diaphyseal compact bone as a plug; 2) metaphyseal cartilage do not reduce in thickness during ageing; 3) metaphyseal cartilage do not show vascular invasion and do not mineralize in degenerative zone; 4) trabecular bone was not at all evident in this animal; 5) external periosteum is well vascularized and proliferates in correspondence to marginal epiphyseal end of the diaphyseal. From these results the hypothesis that the ranid frog bone growth is not due to metaphyseal metabolism (as in avian and mammals) but to bone periosteal marginal mineralization is reached
The fibrillar organisation of the osteon and cellular aspects of its development : a morphological study using the SEM fractured cortex technique.
No full textMorphometry and patterns of lamellar bone in human Haversian system
No full textThe lamellar architecture of secondary osteons (Haversian systems) has been studied with scanning electron microscopy (SEM) in transverse sections of human cortical bone. Na3PO4 etching was used to improve the resolution of the interface between neighboring lamellae and the precision of measurements. These technical improvements permitted testing of earlier morphometry assumptions concerning lamellar thickness while revealing the existence of different lamellar patterns. The mean lamellar thickness was 9.0 +/- 2.13 mu m, thicker and with a wider range of variation with respect to earlier measurements. The number of lamellae showed a direct correlation with the lamellar bone area, and their thickness had a random distribution for osteonal size classes. The circular, concentrical pattern was the more frequently observed, but spiral and crescent-moon-shaped lamellae were also documented. Selected osteons were examined by either SEM or SEM combined with polarized light microscopy allowing comparisons of corresponding sectors of the osteon. The bright bands observed with polarized light corresponded to the grooves observed in etched sections by SEM. The dark bands corresponded to the lamellar surface with the cut fibrils oriented approximately longitudinally along the central canal axis. However, lamellae with large and blurred bright bands could be observed, which did not correspond to a groove observed by SEM. These findings are in contrast with the assumption that all the fibril layers within a lamella are oriented along a constant and unchangeable angle. The different lamellar patterns may be explained by the synchronous or staggered recruitment and activation of osteoblasts committed to the osteon's completion. Anat Rec, 2012. (C) 2012 Wiley Periodicals, Inc
L'achitettura collagenica del dito umano evidenziata con la tecnica di Othani: studio tridimensionale al MES
No full textL'achitettura collagenica del dito umano evidenziata con la tecnica di Othani: studio tridimensionale al MES
No full textMorphological Features of Different Regions in Frog Crista Ampullaris (Rana esculenta)
No full textThe cellular organization of different regions of the crista epithelium from the frog posterior semicircular canal was studied by light, transmission and scanning microscopy. The sensory epithelium consists of hair cells surrounded by supporting cells and basal cells located close to the basement membrane. Three types of hair cells, namely club-like, cylindrical and pear-like cells differentially distributed along the crista could be recognized on the basis of their shape. Club-like cells are located only in the peripheral regions, cylindrical cells both in the central and in the peripheral regions, and pear-like cells appear segregated into the intermediate regions. Sensory cells of the central region are characterized by a ciliary apparatus consisting of stereocilia usually shorter--and in some cases less numerous--than those of cells of the other regions. The presence of large evaginations of the apical membrane of hair cells and of several vesicles of microexocytosis demonstrates that receptor cells have a considerable secretory activity. This secretory activity is also proven by the presence in the supranuclear region of hair cells of numerous Golgi complexes. Moreover, the presence of two kinds of Golgi complexes, one constituted by dilated cisternae containing a moderately electron-dense material and the other made up of flattened electron-transparent cisternae, suggests a diversified secretion of material by the hair cells. This heterogeneous material may provide substances important for cupula formation and the composition of the endolymph
Anatomy of the intracortical canal system. Scanning electron microscopy study in rabbit femur.
No full textThe current model of compact bone is that of a
system of longitudinal (Haversian) canals connected by
transverse (Volkmann’s) canals. Models based on histology
or microcomputed tomography lack the morphologic detail
and sense of temporal development provided by direct
observation. Using direct scanning electron microscopy
observation, we studied the bone surface and structure of
the intracortical canal system in paired fractured surfaces in
rabbit femurs, examining density of canal openings on
periosteal and endosteal surfaces, internal network nodes
and canal sizes, and collagen lining of the inner canal
system. The blood supply of the diaphyseal compact bone
entered the cortex through the canal openings on the
endosteal and periosteal surfaces, with different morphologic
features in the midshaft and distal shaft; their density
was higher on endosteal than on periosteal surfaces in the
midshaft but with no major differences among subregions.
The circumference measurements along Haversian canals
documented a steady reduction behind the head of the
cutting cone but rather random variations as the distance
from the head increased. These observations suggested
discontinuous development and variable lamellar apposition
rate of osteons in different segments of their trajectory.
The frequent branching and types of network nodes suggested
substantial osteonal plasticity and supported the
model of a network organization. The collagen fibers of the
canal wall were organized in intertwined, longitudinally
oriented bundles with 0.1- to 0.5-lm holes connecting the
canal lumen with the osteocyte canalicular system
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