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  • 1
    Digitale Medien
    Digitale Medien
    The human brain at stages 18–20, including the choroid plexuses and the amygdaloid and septal nuclei (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 285-306 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human brain ; Amygdaloid nuclei ; Septal nuclei ; Choroid plexus ; Cerebellum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The development of the human brain during the seventh embryonic week was studied in serial sections of 88 embryos, and graphic reconstructions were prepared. From stages 18 to 20 the cerebral hemispheres expand rapidly and become more and more distinct entities. The longitudinal fissure between them occupies approximately half of their rostrocaudal extent. In stage 20 they have progressed so far in organization that functional aspects (based on synapses in the primordial plexiform layer) are of importance. An advanced differentiation is also present in the amygdaloid body, which has at least four individual nuclei, and in the forebrain septum, which shows the nucleus of the diagonal band and the medial septal nucleus. This has a bearing on recent experimental studies that document the fundamental role of the septal nuclei with regard to behavioural and cognitive functions. Fibre connections between septal nuclei and hippocampus have appeared. A definitive internal capsule, however, is not yet present. The main connections with diencephalon and other parts of the brain are chiefly by fibres to or from the amygdaloid body by way of the lateral forebrain bundle. The olfactory areas are connected with the habenular nuclei by a well developed stria medullaris thalami. Globus pallidus externus, entopeduncular nucleus, and subthalamic nucleus are prominent features in the subthalamus. The main nucleus of the oculomotor nerve shows a dorsolateral and a ventromedial portion. The rhombic lip is mitotically active in all parts of the rhombencephalon, and seems to participate significantly in the formation of the intermediate layer of the cerebellum and of the cochlear nuclei. The sensory nucleus of the trigeminal nerve has appeared. In the cerebellum the cell layer thought to contain the future Purkinje cells develops. The cerebellar plate is organized into external and internal bulges, and is now connected with mid- and hindbrain through fibre bundles. The area thought to be the dentate nucleus and the supposed floccular region are especially rich in fibres. The accessory olivary nucleus appears in stage 19, and accessory nuclei of the abducent and hypoglossal nerves are evident in stage 20. The choroid plexuses of the fourth and lateral ventricles have appeared. In view of their advanced features, the study of embryos of stages 19–21 becomes increasingly relevant to questions of tissue transplanation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00185521
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  • 2
    Digitale Medien
    Digitale Medien
    The development of the human brain and the closure of the rostral neuropore at stage 11 (1986)
    Springer
    Anatomy and embryology 175 (1986), S. 205-222 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Neural tube ; Rostral neuropore ; Neural crest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Twenty embryos of stage 11 (24 days) were studied in detail and graphic reconstructions of twelve of them were prepared. The characteristic feature of this stage is 13–20 pairs of somites. The notochord sensu stricto appears first during this stage, and its rostral and caudal parts differ in origin. Rostrally, the notochordal plate is being transformed into the notochord in a caudorostral direction. The caudal part, however, arises from the axial condensation in the caudal eminence in a rostrocaudal direction. The caudal eminence (or end bud) represents the former primitive streak. The somites are increasing in number at a mean rate of 6.6 h per pair. The rostral neuropore closes towards the end of stage 11. The closure is basically bidirectional, being more rapid in the roof region and producing the embryonic lamina terminalis and future commissural plate in the basal region. The caudal neuropore is constantly open. The brain comprises telencephalon medium (represented by the embryonic lamina terminalis) and a series of neuromeres: 2 for the forebrain (D1 and D2), 1 for the midbrain, and 6–7 for the hindbrain (RhA-C; Rh D is not clearly delineated). The forebrain still occupies a small proportion of the total brain, whereas the spinal part of the neural tube is lengthening rapidly. Some occlusion of the lumen of the neural tube was noted in 4 embryos, all of which had an open rostral neuropore. Hence there is at present no evidence that occlusion plays a role in expansion of the human brain. The marginal (primordial plexiform) layer is appearing, particularly in rhombomere D and in the spinal portion of the neural tube. The neural crest is still forming from both the (open) neural groove and the (closed) neural tube, and exclusively from both neural (including optic) and (mainly) otic ectoderm. The optic sulcus is now prominent, and its wall becomes transformed into the optic vesicle towards the end of stage 11. At this time also, an optic sheath derived from mesencephalic crest and optic crest is present. The mitotic figures of the optic neural crest are exceptional in being situated in the external part of the neural epithelium. The otic pit is becoming deeper, and its wall is giving rise to neural crest that is partly added to the faciovestibulocochlear ganglion and partly forms an otic sheath. The nasal plate does not yet give off neural crest.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00389597
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  • 3
    Digitale Medien
    Digitale Medien
    The development of the human brain from a closed neural tube at stage 13 (1988)
    Springer
    Anatomy and embryology 177 (1988), S. 203-224 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Secondary neurulation ; Neurat tube ; Neurat crest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Twenty-five embryos of stage 13 (28 days) were studied in detail and graphic reconstructions of seven of them were prepared. Thirty or more somitic paris are present, and the maximum is possibly 39. The notochord is almost entirely separated from the neural tube and the alimentary epithelium, and its rostral tip is closely related to the adenohypophysial pocket. Caudal to the cloacal membrane, the caudal eminence is the site of secondary neurulation. The eminence, which usualy contains isolated somites, in the area where new notochord, hindgut, and neural tube are forming. The neural cord develops into neural tube without the intermediate phase of a neural plate (secondary neurulation). Canalization is regular and the lumen is continuous with the central canal. The neural tube is now a closed system, filled with that may be termed “ependymal fluid.” The brain is widening in a dorsoventral direction. Neuromeres are still detectable. The following features are distinguishable: infundibular area of D 2, chiasmatic plate of D 1, “adult” lamina terminalis, and commissural plate (at levels of nasal plates). The beginning of the synencephalon of D 2 can be discerned. The retinal and lens discs are being defined. The mesencephalic flexure continnues to diminish. The midbrain possesses a sulcus limitans, and the tegmentum may show the medial longitudinal fasciculus. The isthmic segment is clearly separated from rhombomere 1. Lateral and ventral longitudinal fasciculi are usually present in the hindbrain, and the common afferent tract is beginning. Somatic and visceral efferent fibres are seen in certain nerves: 6, 12, 5, 7, 9–11. The first indication of the cerebellum may be visible in the alar lamina of rhombomere 1. The terminal-vomeronasal crest appears. Various cranial ganglia (e.g., vestibular, superior ganglia of 9, 10) are forming. The trigeminal ganglion may show its three major divisions. Epipharyngeal placodes of pharyngeal arches 2 to 5 contribute to cranial ganglia 7, 9, and 10. The spinal neural crest is becoming segregated, and the spinal ganglia are in series with the somites. Ventral spinal roots are beginning to develop.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00321132
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  • 4
    Digitale Medien
    Digitale Medien
    The development of the human brain, including the longitudinal zoning in the diencephalon at stage 15 (1988)
    Springer
    Anatomy and embryology 179 (1988), S. 55-71 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Amygdaloid body ; Diencephalon ; Cerebellum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Twenty-six embryos (6–11 mm) of stage 15 (approximately 33 days) were studied in detail and graphic reconstructions of three of them were prepared. Characteristic features of this stage include closed lens vesicles, presence of nasal pits, and retinal pigment. The neuromeric pattern is still visible. Each cerebral hemisphere is limited by the torus hemisphericus internally and by the di-telencephalic sulcus externally. The medial (diencephalic) eminence of the basal nuclei (previously misinterpreted by others as the lateral) had appeared in stage 14, and the lateral eminence, which is telencephalic, is now distinguishable. The amygdaloid body in stages 14 and 15 is derived from the medial eminence. The hippocampal thickening is identifiable in the dorsomedial part of the cerebral hemisphere. Medial and basal forebrain bundles are developing. The olfactory eminence is visible. Future olfactory bulb and tubercle possess an intermediate layer. The wall of the diencephalon presents five longitudinal zones: epithalamus, dorsal thalamus, ventral thalamus, subthalamus, and hypothalamus. The primordium of the epiphysis cerebri is beginning in the more advanced embryos. The sulcus limitans ends rostrally at the midbrain (M1) and is not continuous with the hypothalamic sulcus. Hence the alar/basal distinction does not arise in the forebrain. In the roof of the midbrain (M2) the mesencephalic evagination already noticed at stage 14 is characteristic. It is suggested that it may function as a temporary circumventricular organ. The precursors of some new tracts are identifiable: habenulo-interpeduncular, medial tectobulbar, and mamillotegmental fibres. Commissures include the supramamillary, that of the superior colliculi, and (in some embryos) the first fibres of the posterior commissure. Nuclei include the habenular, mamillary, and probably subthalamic. The cerebellum, the beginning of which was already noted at stages 13 and 14, consists of (1) a rostral part that arises from the alar plate of the isthmic segment and will form the superior medullary velum and part of the corpus cerebelli; and (2) a caudal part that develops from rhombomere 1. The involvement of the isthmic segment, first elucidated with stage 14, has not been observed in previous reports. All cranial nerves except the olfactory and optic are present in the more advanced embryos.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305100
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  • 5
    Digitale Medien
    Digitale Medien
    The development of the human brain, the closure of the caudal neuropore, and the beginning of secondary neurulation at stage 12 (1987)
    Springer
    Anatomy and embryology 176 (1987), S. 413-430 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Caudal neuropore ; Neural crest ; Secondary neurulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Twenty-four embryos of stage 12 (26 days) were studied in detail and graphic reconstructions of five of them were prepared. The characteristic features of this stage are 21–29 pairs of somites, incipient or complete closure of the caudal neuropore, and the appearance of upper limb buds. The caudal neuropore closes during stage 12, generally when 25 somititc pairs are present. The site of final closure is at the level of future somite 31, which corresponds to the second sacral vertebral level. Non-closure of the neuropore may be important in the genesis of spina bifida aperta at low levels. The primitive streak probably persists until the caudal neuropore closes, when it is replaced by the caudal eminence or end-bud (Endwulst oder Rumpfknospe). The caudal eminence, which appears at stage 9, gives rise inter alia to hindgut, notochord, caudal somites, and the neural cord. The material for somites 30–34 (which appear in stage 13) is laid down during stage 12, and its absence would be expected to result in sacral agenesis. Aplasia of the caudal eminence results in cloacal deficiency and various degrees of symmelia. The junction of primary and secondary development (primäre und sekundäre Körperentwicklung) is probably at the site of final closure of the caudal neuropore. Secondary neurulation begins during stage 12. The cavity of the already formed spinal cord extends into the neural cord, and isolated spaces are not found within the neural cord. Primary and secondary neurulation are probably coextensive with primary and secondary development of the body, respectively. The telencephalon medium has enlarged two mesencephalic segments (M1 and M2) are distinguishable, and rhombomere 4 is reduced. The sulcus limitans is detectable in the spinal cord and hindbrain (RhD), and in the mesencephalon and diencephalon, where it extends as far rostrally as the optic sulcus in D1. A marginal layer is appearing in the rhombencephalon and mesencephalon. The first nerve fibres are differentiating, chiefly within the hindbrain (from the nucleus of the lateral longitudinal tract). Optic neural crest is at its maximum, and the otic vesicle is giving crest cells to ganglion 7/8. Neural crest continues to develop in the brain and contributes to cranial ganglia 5, 7/8, and 10/11. The spinal crest extends as far caudally as somites 18–19 but shows no subdivision into ganglia yet. Placodal contribution to the trigeminal ganglion is not certain at stage 12. Such a contribution to ganglion 7/8 is not unlikely. Involvement of neural crest in the formation of the derivatives of pharyngeal arches 1 and 2 is possible but has not yet been confirmed in the human embryo.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00310083
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  • 6
    Digitale Medien
    Digitale Medien
    The human brain at stage 17, including the appearance of the future olfactory bulb and the first amygdaloid nuclei (1989)
    Springer
    Anatomy and embryology 180 (1989), S. 353-369 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human brain ; Cerebral hemispheres ; Amygdaloid nuclei ; Olfactory bulb ; Cerebellum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The growth of the cerebral hemispheres rostrally and caudodorsally brings about a deepening of the interlongitudinal fissure, in which blood capillaries for the future choroid plexus develop. Accumulation of mesenchyme basally presages the formation of the nasal septum. The olfactory bulb and tubercle become outlined. The three main areas of the telencephalon, future archi-, paleo-, and neocortex, can be recognized. The amygdaloid body, which is related to the medial ventricular eminence, contains either one or two nuclei. Nerve fibres from the olfactory tubercle arrive and pass through the amygdaloid area. The first indication of a septal nucleus is recognizable. The lateral ventricular eminence is present but not pronounced. The hemispheric stalk joins the cerebral hemispheres to the ventral thalamus and to the diencephalic part of the medial ventricular eminence. The beginning of the future choroid plexus consists in the formation of blood vessels and necrotic changes in the roof of the telencephalon medium and in rostral growth of the anterior choroid artery. Necrotic processes in the future choroid epithelium are now localized at the periphery of the still multilaminar tissue. The sulcus medius and zona intrathalamica delimit the dorsal from the ventral thalamus. The dimesencephalic borderline passes through the commissural fibres in the roof: the rostral part of the commissure is the posterior commissure, the caudal part, the commissure of the superior colliculi. In the mesencephalon, the red nucleus has a laterorostral position with regard to the nucleus of the oculomotor nerve. The cells of the locus coeruleus are well distinguishable. The gustatory fibres begin to separate from the common afferent tract as the tractus solitarius. Inferior and superior salivatory nuclei are delineated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00311167
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  • 7
    Digitale Medien
    Digitale Medien
    The first appearance of the human nervous system at stage 8 (1981)
    Springer
    Anatomy and embryology 163 (1981), S. 1-13 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Neuroembryology ; Neural groove ; Developmental stages
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Eleven embryos of stage 8 (18 days), including a set of twins, were studied in detail and graphic reconstructions were prepared. This is the first report based on more than two specimens, as well as the first account of embryos of excellent histological quality at this developmental stage. Detailed measurements of the embryos are provided. It is found that the neural groove, which is the first morphological manifestation of the nervous system, is present in one quarter of embryos of stage 8. The neural folds are very largely cerebral rather than spinal. Correlations with other developmental features suggest that the neural groove is seen only when a certain degree of size and maturity has been reached by embryos of this important stage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315766
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  • 8
    Digitale Medien
    Digitale Medien
    The human brain at stages 21–23, with particular reference to the cerebral cortical plate and to the development of the cerebellum (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 375-400 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human brain ; Cortical plate ; Internal capsule ; Cerebellar commissures ; Corpus striatum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The development of the human brain during the eighth embryonic week was studied in serial sections of 22 embryos, and graphic reconstructions were prepared. The cortical plate appears in stage 21 in the area of the future insula and is an excellent feature for staging. The internal capsule contains neocortical fibres. Its three main outlets begin to be present in stage 22 and lead to epithalamus, to dorsal thalamus, and to mesencephalon. At this time a well developed lateral olfactory tract can be seen. The anterior commissure appears in stage 23. A clear developmental relationship between claustrum and olfactory area is described for the first time in human embryos. The optic tract reaches the ventral area of the lateral geniculate body. Scattered fibres of the lateral lemniscus reach at least as far as the caudal mesencephalon, in which superior and inferior colliculi can be distinguished at stage 23; two caudalBlindsäcke containing ventricular recesses form in stage 23. The cerebellum is still present as a plate, but its internal bulge is considerably enlarged. It possesses radially- and tangentially-arranged cells; the latter form the external germinal layer. The dentate nucleus, as well as the inferior and superior cerebellar peduncles and some of the cerebellar commissures, are present. Compared with the highly developed and probably already functional remainder of the hindbrain, the cerebellar plate shows far less differentiation. Two caudal migratory streams (marginal and submarginal) are present and represent the corpus pontobulbare. The decussation of the pyramids appears in stage 23. This article concludes the study of the developing human brain during the embryonic period, from stage 8 to stage 23. The series was based on 340 serially-sectioned embryos and graphic reconstructions from 89 brains. No comparable investigation of the fetal brain is available.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02433497
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  • 9
    Digitale Medien
    Digitale Medien
    The first appearance of the major divisions of the human brain at stage 9 (1983)
    Springer
    Anatomy and embryology 168 (1983), S. 419-432 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Neuroembryology ; Neural plate ; Developmental stages
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Five embryos of stage 9 (20 days) were studied in detail and graphic reconstructions were prepared. This is the first report based on more than one specimen of this rarely seen stage. Detailed measurements of the embryos are provided. The characteristic features of this stage are 1 to 3 pairs of somites, the head fold and foregut, the otic discs, and the pericardial cavity. The primitive streak is not decreasing as rapidly as in stage 8 but the caudal eminence is proliferating. The notochordal plate is not increasing as rapidly as in stage 8 and a notochord is not yet present. It is to be stressed that the 3 major dividions of the brain (prosencephalic, mesencephalic, and rhombencephalic) can be identified in the open neural groove. The rhombencephalon is the dominant feature of the brain and comprises 4 subdivisions, the last of which, previously unrecognized, is related to the (occipital) somites and represents the hypoglossal region. Features that may not be visible include the caudal fold and hindgut, endocardial tubes or plexus, neural crest, and neurenteric canal. In 2 specimens, atria, left ventricle, right ventricle, conotruncus, and first (or first and second) aortic arches are distinguishable. Two of the embryos studied are the earliest examples in which neural crest has been identified.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00304278
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  • 10
    Digitale Medien
    Digitale Medien
    The first appearance of the neural tube and optic primordium in the human embryo at stage 10 (1985)
    Springer
    Anatomy and embryology 172 (1985), S. 157-169 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Human embryo ; Human brain ; Neural tube ; Neural crest ; Optic primordium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Thirteen embryos of stage 10 (22 days) were studied in detail and graphic reconstructions of most of them were prepared. The characteristic feature of this stage is 4–12 pairs of somites. Constantly present are the prechordal and notochordal plates (the notochord sensu stricto is not yet apparent), the neurenteric canal or at least its site, the thyroid primordium, probably the mesencephalic and rhombencephalic neural crest and the adenohypophysial primordium. During this stage, the following features appear: terminal notch, optic sulcus, initial formation of neural tube, oropharyngeal membrane, pulmonary primordium, cardiac loop, aortic arches 1–3, intersegmental arteries, and laryngotracheal groove. The primitive streak is still an important feature. Graphic reconstructions have permitted the detection of the telencephalic portion of the forebrain, for the first time at such an early stage. It is proposed that the remainder of the forebrain comprises two subdivisions: D1, which becomes largely the optic primordium during stage 10, and D2, which is the future thalamic region. The optic sulcus is found in D1 but does not extent into D2, as has been claimed in the literature. An indication of invagionation of the otic disc appears towards the end of the stage. As compared with the previous stage, the prosencephalon has increased in length, the mesencephalon has remained the same, the rhombencephalon has decreased, and the spinal part of the neural plate has increased fivefold in length. The site of the initial closure of the neural groove is rhombencephalic, upper cervical, or both. The neural plate extends caudally beyond the site of the neurenteric canal. Cytoplasmic inclusions believed to indicate locations of great activity were always detected in the forebrain (especially in the optic primordium), and also in the rhombencephalon, spmal part, and mesencephalon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00319598
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