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  • 1
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Serial sections of normal human embryos were studied and three-dimensional images reconstructed to determine the early development of the interventricular septum. The position of the interventricular septum is determined in stage 9 of normal development by the formation of the left interventricular sulcus. As a result of unknown properties of the cells of the myocardial layer, the left interventricular sulcus persists while the right disappears, producing the initial lateral asymmetry of the primary heart tube. By stage 14, the left interventricular sulcus forms a spiral which is continuous with the developing interventricular septum. The dorsal limb of the spiral passes to the right between the atrioventricular canal and the origin of the outflow tract, and is lost in the wall of the trabeculated right ventricle. It appears that this dorsal limb of the spiral is the precursor of part of the cirsta supraventricularis. The midportion of the sulcus, the bulboventricular groove, becomes the socalled fibrous continuity between the aortic and mitral valves. The ventral limb of the spiral passes caudally in the anterior interventricular groove and then dorsally and cranially toward the dorsal cushion of the atrioventricular canal. The ventral limb of the spiral is continuous with the crest of the muscular interventricular septum, which develops by apposition of tissue from the expanding right and left ventricles. From stage 14 to stage 19, the muscular interventricular septum, the atrioventricular endocardial cushions, and the ventricular end of the spiral ridges of the outflow tract appose and fuse. Subsequent formation of the membranous interventricular septum completes the physical separation of the right and left ventricles.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 215 (1986), S. 167-181 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Severe cardiac malformations may involve the atrioventricular valve region, but the sequence of embryonic development of this important area has been little studied. In particular, the basis of atrioventricular muscular discontinuity, except at the conduction system, has remained unexplained. To examine this question, serial histologic sections of human embryos from the Carnegie Embryo-logical Collection and from the Hopkins Pathology Collection were studied and six embryos were reconstructed. The atrioventricular sulcus can be identified in Carnegie stage 10 as an indentation or crease on the right side separating the heart tube from the umbilical vein. By stage 12 the sulcus has deepened and rotated anteriorly as the atria appear and the heart tube elongates rapidly within the confining pericardial space. Selective accumulation of cardiac jelly on the endocardial aspect of the constriction of the heart tube produced by the atrioventricular sulcus is pronounced by stage 14. By stage 16 the separation of the atrioventricular orifice into right and left components is well advanced, and by stage 18 the septation of the atria and ventricles is largely complete. The muscular connection between the atria and the ventricles becomes interrupted around most of the artioventricular sulcus, except for the His bundle, during the latter part of the embryonic period. The topography of the original sulcus assumes a catenoidal or saddle-shaped configuration, i.e., convex in one plane and concave in the perpendicular plane. The tension and pressure relationships in such a structure would favor cardiac jelly accumulation and the eventual disintegration of lines of myocyte connections passing across the groove. The preservation of the His bundle connection is explained by the failure of the sulcus to completely encircle the heart.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 201 (1981), S. 635-640 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The development of the lung in 25 human embryos and early fetuses up to 140 mm crown-rump length was studied by examination of serial histologic sections, morphometry, and selected reconstructions. The proportion of pulmonary tissue consisting of tracheobronchial tree increases during this period. Bronchial cross-sectional diameter, length of the most distal bronchial branches, and thickness of the distal mesenchyme decline during development. The results are consistent with the concept that the dichotomous branching of the growing tracheobronchial tree occurs because of resistance to forward growth of the bronchial branch by compressed mesenchyme, pleura, or adjacent structures. Division and further growth of the bronchus takes place in areas of lower resistance. This process produces a “filling in” of space available for lung development and brings the epithelial and mesenchymal elements into their definitive relationships.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 216 (1986), S. 544-549 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The factors which give rise to the normal relationship between the great arteries and their respective ventricles are unknown. The developmental anatomy of this region was studied by using frontal, sagittal, or transverse serial histologic sections of 17 normal human embryos of Carnegie stages 15-19 from the Carnegie Embryological Collection. Distances and angles between major anatomic landmarks were determined by using computer reconstructions of the serially sectioned embryos, three-dimensional analytic geometry, and Euclidean distance formulas. The findings show that between stages 15 and 19 there is a marked rotation of the axis of the semilunar valves: frontal 121° counterclockwise, sagittal 196° counterclockwise, and transverse 240° clockwise. Simultaneously the great arteries lengthen at a faster rate than the rest of the heart; and there is also an increase in the caliber and wall thickness of the great arteries. These results suggest that the changing rate of growth between the great arteries and the heart is necessary to align the great arteries, the semilunar valves, and the muscular outflow tract septum appropriately with respect to the interventricular septum. Reductions in the rate of growth of the great arteries relative to the heart could, by causing changes in the rotation of great arteries and outflow tract septum, have a role in the pathogenesis of cardiovascular malformations such as tetralogy of Fallot and transposition of the great arteries.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 198 (1980), S. 245-254 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Connective tissue provides dynamic stability to the architecture and mechanical function of the lungs. This study examines the parenchymal connective tissue components of the alveolar ducts, their associated respiratory bronchioles and respective alveoli. Thick sections 100μ and 200μ, and serial sections at 8μ of lungs of different ages were examined histologically after fixation in distention. The varying proportions and spatial architecture of the collagen and elastic fibers and the packing and spatial interrelationships of alveoli were studied using graphic serial reconstruction. Alveolar mouths typically have a polygonal configuration as they arise from the airways. Denser connective tissue passes through the polygonal array and forms a helix encircling the airway. Polygonal packing of alveolar mouths provides a mechanically stable ductular structure with conservation of materials. A helical modification of the polygonal arrangement permits reversible changes in linear and circumferential airway dimensions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The sequence of events in the development of the brain in human embryos, already published for stages 8-15, is here continued for stages 16 and 17. With the aid of a computerized bubble-sort algorithm, 71 individual embryos were ranked in ascending order of the features present. Whereas these numbered 100 in the previous study, the increasing structural complexity gave 27 new features in the two stages now under investigation. The chief characteristics of stage 16 (approximately 37 postovulatory days) are protruding basal nuclei, the caudal olfactory elevation (olfactory tubercle), the tectobulbar tracts, and ascending fibers to the cerebellum. The main features of stage 17 (approximately 41 postovulatory days) are the cortical nucleus of the amygdaloid body, an intermediate layer in the tectum mesencephali, the posterior commissure, and the habenulo-interpeduncular tract. In addition, a typical feature at stage 17 is the crescentic shape of the lens cavity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The sequence of events in the development of the brain in human embryos, already published for stages 8-17, is here continued for stages 18 and 19. With the aid of a computerized bubble-sort algorithm, 58 individual embryos were ranked in ascending order of the features present. The increasing structural complexity provided 40 new features in these two stages. The chief characteristics of stage 18 (approximately 44 postovulatory days) are rapidly growing basal nuclei; appearance of the extraventricular bulge of the cerebellum (flocculus), of the superior cerebellar peduncle, and of follicles in the epiphysis cerebri: and the presence of vomeronasal organ and ganglion, of the bucconasal membrane, and of isolated semicircular ducts. The main features of stage 19 (approximately 48 days) are the cochlear nuclei, the ganglion of the nervus terminalis, nuclei of the prosencephalic septum, the appearance of the subcommissural organ, the presence of villi in the choroid plexuses of the fourth and lateral ventricles, and the stria medullaris thalami.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 160 (1981), S. 309-331 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The majority of congenital heart malformations in humans involve defects in the atrioventricular valves, the crest of the interventricular septum, and/or the outflow tract, but the position and timing of these structures during cardiac development is controversial. We examined all 622 staged, serially sectioned normal human embryos and fetuses in the Carnegie Embryological Collection, and obtained a statistical tabulation of the appearance of the endocardial cushion components and surrounding structures for 382 embryos in good condition between stages 9 and 23 inclusive, when the heart normally develops. Accurately scaled drawings of ventral and lateral views of the hearts of seven embryos from stage 13 through 22 were prepared from graphic reconstructions in order to visualize the relationships of the structures under consideration. We found that development of the outflow tract septum follows the apparent functional separation of both the left and right ventricles and the blood streams leaving them. Elevations of the endocardial cushion material are continuous throughout the outflow tract and develop as a consequence of the elliptical configuration imposed on the circular cross section of the outflow tract. The membranous interventricular septum is formed of cushion material in the space bounded by the outflow tract septum, interventricular septum, and the fused AV cushion and right outflow tract cushion. The results of this study are consistent with the assertion that functional separation of the aortic and pulmonary outflow tracts precedes anatomic septation, and that anatomic septation is brought about by mechanical modeling of developing myocardium and endocardial cushion material.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 167 (1983), S. 313-327 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The reason that the normal ductus arteriosus has a muscular media, contrasting with the elastic lamellar structure of the adjacent great arteries, is unknown. We examined the hypothesis that the anatomic relationship of the ductus arteriosus to the vagus and recurrent laryngeal nerves during early development might be of importance in influencing ductal morphology. Normal human embryos from the Carnegie Embryological Collection and embryos and fetuses from the Hopkins Pathology Collection were studied microscopically, by reconstructions made from serial histologic sections, or by gross dissection. At Carnegie stage 16 the recurrent laryngeal nerves pass medially from the vagus nerve to the laryngeal area and are caudal to the bilaterally symmetric sixth aortic arches. By stage 18 the right sixth aortic arch has disappeared and the left sixth aortic arch is in a more caudal position relative to the larynx. The left vagus nerve and its recurrent laryngeal branch form a sling supporting the distal (or ductus arteriosus component) of the left sixth aortic arch. In subsequent development there is greater relative separation of the larynx and ductus arteriosus. The media of the ductus arteriosus beneath the supporting nerves is thinner and has less elastic fiber formation than the elastic lamellar media of the adjacent aortic arches. The study shows that the vagus and recurrent laryngeal nerves are in a position to provide mechanical support to the ductus arteriosus during its development and that the morphology of the media of the supported ductus arteriosus differs from that of the adjacent unsupported aortic arches. It is suggested that this local mechanical support may be the reason that the normal ductus arteriosus differentiates as a muscular artery and is therefore able to obliterate its lumen in postnatal life. Without such support the ductal media could develop the abundant elastic fibers characteristic of the normal unsupported aorta and pulmonary trunk and become an abnormal, persistently patent ductus arteriosus.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The sequence of events in the development of the brain in staged human embryos was investigated in much greater detail than in previous studies by listing 100 features in 165 embryos of the first 5 weeks. Using a computerized bubble-sort algorithm, individual embryos were ranked in ascending order of the features present. This procedure made feasible an appreciation of the slight variation found in the development features. The vast majority of features appeared during either one or two stages (about 2 or 3 days). In general, the soundness of the Carnegie system of embryonic staging was amply confirmed. The rhombencephalon was found to show increasing complexity around stage 13, and the postoptic portion of the diencephalon underwent considerable differentiation by stage 15. The need for similar investigations of other systems of the body is emphasized, and the importance of such studies in assessing the timing of cogenital malformations and in clarifying syndromic clusters is suggested.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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