Csilla Hegedűs, Gogolak H. Edit University of Medicine and Pharmacy, Târgu- Mureş, Romania

THE MODELING OF NEURULATION-EMBRYOLOGICAL TEACHING METHODS

Csilla Hegedűs, Gogolak H. Edit

University of Medicine and Pharmacy, Târgu- Mureş, Romania


The forming and closing of the sulcus neuralis, the presence of the former anterior and posterior neuroporus, under the inductive action of the dorsal chord are represented on 5 casts, 8 casts are representing metamerisation of the neural folds.


The neurulation that follows the genesis of the blastocist and the gastrulating has been reproduced in tridermic state


The casts are the reciprocal materialization of the neural tube and the structure adjoin it.The formation of the neural plate is lead by the cordomezoblast


The forming and closing of the sulcus neuralis. As a result of such unequal growth is folded into neural groove by the time somites appearing

,

Origin of the neural tube and neural crest, as illustrated by transverse section from early human embryos, stereogram of primordial spinal cord



Mesodermal sheets extend laterally from the midplane and at the margin of the embryonic disc become continuous with extraembyonic mesoderm

Mesoderma


The neural groove itself is bounded on each side by an elevated neural fold. At first this neural plat is flat and but a single layer of cell thick. However, it rapidly stratified and lateral margins grow faster than the central region


The groove continues to deeped and the tickened neural folds presently meet and fuse dorsally, thereby rolling the original plate into a neural tube. The groove begins to close near the midle of the body in embryos with 6 somites and closure advances progressively in both directions


With continued growth of the embryo caudally, the neural groove extends steadly in that direction.The open caudal end of the neural tube is called posterior neuropore, it closed off at about the 30 somite stage


The neural axis in embryos 2 mm long (and with some 7 somites) is still nearly straight, but its rostral end is enlarging into primitive brain. Even before this region of the neural groove has closed, three points of expansion apears


Separated by two retarded zones of relative constriction subdivide the brain in three parts the forebrain (prosencephalon), the mid-brain (mesencephalon) and the hind-brain (rhombencephalon)


Both the fore- and hind-brain vesicle promptly give rise two secondary vesicles, whereas the mid-brain reamains permanently undivided. The fore-brain subdivides in into the telencephalon, with its primitive cerebral hemispheres


Diencephalon which bears the optic vesicles. The mid-brain ratains its original designation, the mesencephalon. At 7 mm (five weeks) the neuropores have closed and the hind-brain constricts int metencephalon, or future region of the cerebellum and pons, and into myelencephalon or medulla oblongata


While the several divisions of the brain are differentiating, certain flexures appear in the roof and floor, due largely to unequal growth processes. The first, or cephalic flexure appears in the mid-brain region


Next two other flexures gain prominence at about the same time. These are cervical flexure, at the junction of brain and spinal cord and pontine flexure in the region of the future pons


At the junction of the caudal portion of roof plate an interesting derivate is the epiphysis or pineal body. The epiphysis of mammals, birds and some reptiles differentiated in quite a different direction.The cavity of the diencephalon is the third ventricle, remains preponderantly composed of gray nuclear matter


The rest of diencephalon consists of three main regions: the epithalamus dorsally the thalamus laterally and hypothalamus ventrally. Epi- and hypothalamus are more primitive character and their differentiation precedes that of thalamus which is best developed in higher vertebrates


The front end of the neural tube consists of median portion, continuous with diencephalon and two lateral hemispheric outpouchings from it. The neopallium is very large in mammals and constitutes almost all the exposed portions of human cerebrum


Two hemispheres grow forward on each side of it, the lamina terminalis (median band in unchanged position) becomes buried at the bottom of the resulting longitudinal fissure. In middle of the 4th foetal month


The surface extent of the cerebral wall. The thin gray cortex, increases more rapidly the white medullary layer whish underlies it. As a result, the cortex is folded into convolutions between which are prominent furrows, termed fissures. The first fissures appear are the rhinal and hippocampal fissures


At about the same time , the lateral fissure (of Sylvius) makes appearance but is not completed until after birth. Its development is due to the fact that the cortex overlying (the corpus striatum) expands more slowly than do the surrounding areas, this region is consequently overgrown by opercular folds (of the frontal, parietal and temporal lobes)


Right half of the human brain in lateral view, the area opercularis thus incompletly enclosed is the insula (island of Reil), and the depression so formed is the lateral fissure

Brain of human foetus in ventral view, olfactory lobe (olfactory bulb, olfactory tract), optic

nerve, chiasma opticum infundibulum


Lateral and basal views the human telencephalon (lysencephalon). The rhinencephalon during in sixth weeks a swelling appears on the ventral surface of each hemisphere. These enlarge into distinct olfactory lobes, however, remain small in man


CONCLUSIONS

The casts pieces, exposed in the Museum of Anatomy and Embryology from of the University of Medicine and Pharmacy Tg. Mureş represents the epigenetic stages of the embryo-fetogenic development of the central nervous system and the decisive moments of neurohistogenesis.


CONCLUSIONS

The use of gypsum 13 cast pieces is organically completing the visual, auditiv and proprioceptive learning methods.Increasing the number of the casts assures o larger acces of the demonstrative material. The classical method of gypsum casts has been partialy replaced by high resolution microscopes guided by softwares capable of transforming plane pictures to 3D images.

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Csilla Hegedűs, Gogolak H. Edit University of Medicine and Pharmacy, Târgu- Mureş, Romania