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Embryology started in the XIXe eeuw as a morphological study. Edouard Van Beneden contributed largely to its development through his works on the female sexual cell and on the development of the tunicates. But since 1985 the new era of molecular embryology is opening. Large therapeutic applications will be available in the near feature.
The neurological and embryological work of Santiago Ramon y Cajal appeared in three stages: a) Between 1888 and 1893 observations on the development of neuron prolongations led to the observation of the growth cone and formulation of the neurotropic hypothesis. b) Between 1905 and 1908 the study of regenerative phenomena in nerves and nervours centers presented a large body of evidence consistent with the neurotropic hypothesis. c)Between 1910 and 1914 an experimental program was undertaken to test the neurotropic hypothesis; this program led to conclusions on the origin and chemical nature of the growth stimulating factor. These contributions initiated an important line of research that none of Ramon y Cajal's disciples could continue. In the nineteen fifties a group of researchers from three disciplines (biochemistry, embryology and neurohistology) discovered the existence of nerve growth factor (NGF), thus initiating a fertile new field of knowledge in cell biology.
In current biological and philosophical literature, the use of the terms epigenesis and epigenetics has increased tremendously. As these terms are often confused, this paper aims at clarifying the distinction between them by drawing their conceptual and historical evolutions. The evolution of the term epigenesis is situated in the context of early embryological studies. Departing from Aristotle's natural philosophy, it is shown that epigenesis gained alternating attention from the 17th century onwards, as it was introduced into neo-classical embryology and considered to be the opposite of the preformationist tradition. Where preformation stated that the germ cells of each organism contain preformed miniature adults that unfold during development, epigenesis held that the embryo forms by successive gradual exchanges in an amorphous zygote. Although both traditions tried to explain developmental organization, religious and metaphysical arguments on the conception of embryonic matter as either active or passive determined the scope of their respective explanations. It is shown that these very arguments still underlie the use of gene-centric metaphors in the molecular revolution of the 20th century.
The Department of Histology and Embryology at Kaunas University was established in 1923. Professor E. Landau was the very first to head the Department. He arrived in Kaunas from the University of Bern (Switzerland) and worked here from 1923 till 1932. At that time the staff of the Department had only four people: professor E. Landau, head of the Department, J. Bubenaite, senior assistant, D. Kesiūnaite, assistant, and J. Masevicius, laboratory assistant. From 1934 till 1937 the Department was headed by professor V. Danchakova, who came from Columbian University in New York. From 1939 till 1971 the Department was headed by professor B. Abraitis, and from 1971 till 1994 by professor A. Vitkus. In 1994 associate professor K. Baltrusaitis was elected head of the Department. At present time the staff has five lecturers and four laboratory assistants. Various preparations for histology classes are being produced by the laboratory and teaching personnel. According to the curriculum requirements, lectures courses of histology, cytology and embryology are delivered to the first and second year students of the Faculties of Medicine, Odontology, Nursing and Public Health, taking into account specific aspects of each speciality. An optional course is also provided to senior students wishing to study the problems of histogenesis and changes associated with aging of body tissues. In 2003 professor A. Valanciūte was elected head of the Department. The main research problem deals with experimental ischemic heart disease and the solution of problems of experimental myocardial infarction. The results of all thesis research works can be summed pointing out 12 presented inventions and more than 20 rationalizations. Staff of the Department also takes part in the realization of an international project called "Biotechnet".
The teaching of Oral Histology and Embryology clinically integrated was designed as a pilot experience to be developed during the 2005 academic year at the Division of Histology and Embryology (Chair "A") of the National University of Cordoba School of Dentistry. This experience, in which the members of the faculty of the Department of Clinical and Basic Sciences have an active participation, is based on a systemic conception of the learning-teaching process and on the recommendations made by the OPS/OMS. This approach will allow us to optimize the quality of our undergraduate programs through better teacher training and the gradual integration of basic and clinical sciences. Our aim is to provide a better education with clinical relevance in basic sciences and scientific basis in clinical assistance.
The paper analyzes the clinical aspects of medical embryology, emphasizes the topical problems of progenesis, fertilization, cleavage, gastrulation, implantation, and histo-, organo-, and systemogenesis. The current status of the studies into the mother-fetus system is explored. The new organizational patterns of the connection between theory and practice, which enables medical embryology to substantially affect the health care system are also discussed.
The life and work of Prof. MUDr. Zdenek Frankenberger is presented with the main focus on the 16-year period of his activities in Slovakia. His contribution to the history of the Bratislava School of Medicine is great both with regard to his activities both as its founder and excellent teacher of generations of Slovak doctors. He was striving hard to establish the Institute of Histology and Embryology whose first head he became. He participated in the establishment and development also of other institutes of the School of Medicine. An analysis of his remarkable and voluminous scientific work displays the extent of his education, knowledge and interests. His studies covered a broad range of scientific problems in the field of histology, microscopic anatomy, embryology, comparative anatomy and anthropology. Yet he was engaged also in faunal studies and became a reknown expert in entomology. Prof. Frankenberger contributed considerably to the executive work of the Medical School and was its vice-dean and dean.
Human embryology was founded 100 years ago by WILHELM HIS, who may rightly be called the "Vesalius of human embryology". 3 landmarks were published in Germany within a quarter of a century: The Anatomie menschlicher Embryonen of HIS, KEIBEL'S Normentafeln, and KEIBEL and MALL'S Handbuch der Entwicklungsgeschichte des Menschen. The staging of the human embryo, now associated with the names of STREETER and O'RAHILLY, was first proposed by MALL in Anatomischer Anzeiger.
Tredern's thesis on chick embryo development was submitted in Jena (Germany) in 1808 and seems to have been completely overlooked by historians of embryology during the 20th century. However, K.E. von Baer and C. Pander were much interested in that thesis in 1816-1817, when they resumed work on the chick embryo. Tredern, who was born in France in 1780, had then left Germany and abandoned his studies, but von Baer tried to find trace of him throughout his life, wanting to pay homage to his pioneer work. Von Baer published a short biographical notice (1874), which was later extended by Stieda (1901). The accuracy of Tredern's observations and the reasons that could have justified von Baer's interest are discussed. Tredern went back to Paris in 1811 to submit a second medical thesis, the value of which is also considered. It is also shown that, in the teaching of embryology, 18th century preformation concepts were still vivid, remaining in French textbooks of the period 1800-1830. This situation strongly contrasts with the new epigenetic views that were developed by the German scientists with whom Tredern had performed his studies.
In connection with the decade of the first test-tube children appearance in Russia a contribution of medical embryology to the working out of auxiliary reproduction method is discussed. The significance of close interaction and mutual understanding between embryologists and representatives of other professions (gynaecologists, endocrinologists and geneticists) in successful solving of the problem is emphasized Main stages of the modern reproductive technology forming were followed up so as the role of medical embryology in sterility treatment. Certain ethic and lawful problems concerning reproduction including the limits of research on human embryos were discussed.
Under consideration are principle conceptions of G. A. Shmidt on the ecological method in embryology: succession between the compared species, difference in the ecology and organization of adult individuals, distinctions in the course of embryogenesis. Difficulties in a strict observation of all these principles are analyzed in comparative embryological investigations. Possible use of the above principles for studying the intrespecies variability of ontogenetical processes is shown.
A review of over 1,800 publications concerning the embryology and pathologic anatomy of conjoined twins provides convincing evidence that they all result from the secondary union of two originally separate monovular embryonic discs. This "fusion" theory seems to be confirmed by the adjustments to union and the pattern and incidence of specific anomalies at the proposed sites of conjunction in more than 1,200 cases, all of which can be arranged in two uninterrupted series of cases, the one united dorsally (in the neural tube) and the other, ventrally (over a shared a yolk sac). No theoretical "fission" of the vertebrate embryo at any stage of development, in any plane, in any direction can explain (1) the selection of the observed sites of fusion, (2) the details of the union, or (3) the limitation to the specific areas in which the twins are found to be joined. Part I of this disquisition deals with the pertinent normal and theoretical embryology, the adjustments to union, and the parasitic cases, as well as conjoined triplets and quadruplets, and a comparison of oviparous and viviparous embryos. Part II (in a subsequent issue of this journal) will compare and correlate the abnormalities of the various organ systems involved in 1,200 cases.
The possibility that cartilages of differing embryological origins behave as separate types with respect to cell-to-cell associations was tested by placing the cut ends of transversely sectioned embryonic chick tibial cartilages (of mesodermal origin) in apposition to transversely sectioned Meckel's cartilages (neural crest (ectodermal) cartilage) on the surface of a semi-solid organ culture medium and maintaining the combinations in vitro for five to ten days. Tibia-tibia and Meckel's cartilage-Meckel's cartilage (homotypic) combinations, which served as controls, became united by a common extracellular matrix and by the proliferation of chondroblasts. Analysis of combinations where one partner had been prelabelled with 3H-thymidine indicated that chondroblasts intermingled at the contact zone. In contrast, tibia-Meckel's cartilage (heterotypic) combinations became separated by a layer of fibrous tissue. The chondroblasts at the contact zone failed to intermingle. We conclude that avian embryonic chondrocytes are not all equivalent and that part of their nonequivalence could be related to their embryological origin either from the mesoderm or from the ectodermal neural crest.
The human pinna has a complex shape and yet the basic components of normal structure are remarkably constant between individuals. It is precocious in its appearance during embryogenesis and it has been subject to many developmental and surgical studies, yet questions remain as to its primary embryogenesis and the causes of its malformations. Unfortunately, the vast majority of clinical reports of syndromes and of individuals with dysmorphic signs provide limited and inadequate description of the external ear. Given the intricate pattern of the pinna, and hence its potential for morphological variation, we think that more attention to the specific description of ear anomalies may lead to a better appreciation of the etiology and embryology of the malformations. Furthermore, in some cases correlation with specific syndromes may provide an aid to diagnosis. Towards those ends this paper reviews some of the controversy concerning the embryology of the pinna, and discusses a number of the better-defined anomalies of the external ear. Although it has been suggested that anomalies of the insertion and orientation of intrinsic muscles of the pinna may be responsible for variations in external ear morphology, we think it likely that in many cases the anomalous insertions may be secondary.
This is the story of a textbook that students of developmental biology have used for 45 years. "An Introduction to Embryology" was released soon after a role for genes in the control of development became finally recognized but not yet well documented. Thus this book manifested the transition from embryology to developmental biology. The story of its author, Boris Balinsky, who against all odds survived to write this book, is remarkable on its own. He started his scientific career in the USSR, but due to 20th century social and political upheavals, ended it in South Africa. This article will shed light on the life of Boris Balinsky, a scientist and writer and will explore the origins of his book.
Textbooks of embryology provide a standard set of drawings and text reflecting the traditional interpretation of phrenic nerve and diaphragm development based on anatomical dissections of embryonic tissue. Here, we revisit this issue, taking advantage of immunohistochemical markers for muscle precursors in conjunction with mouse mutants to perform a systematic examination of phrenic-diaphragm embryogenesis. This includes examining the spatiotemporal relationship of phrenic axon outgrowth and muscle precursors during different stages of myogenesis. Additionally, mutant mice lacking c-met receptors were used to visualize the mesenchymal substratum of the developing diaphragm in the absence of myogenic cells. We found no evidence for contributions to the diaphragm musculature from the lateral body wall, septum transversum, or esophageal mesenchyme, as standard dogma would state. Nor did the data support the hypothesis that the crural diaphragm is of distinct embryological origins. Rather, we found that myogenic cells and axons destined to form the neuromuscular component of the diaphragm coalesce within the pleuroperitoneal fold (PPF). It is the expansion of these components of the PPF that leads to the formation of the diaphragm. Furthermore, we extended these studies to examine the developing diaphragm in an animal model of congenital diaphragmatic hernia (CDH). We find that malformation of the PPF mesenchymal substratum leads to the defect characteristic of CDH. In summary, the data demonstrates that a significant revision of narratives describing normal and pathological development of the diaphragm is warranted.
BACKGROUND: Paragangliomas are unusual tumors in the head and neck originating from the paraganglia or glomus cells of neural crest origin. METHODS: We describe the first case of a primitive paraganglioma of the floor of the mouth presenting in childhood. RESULTS: Complete surgical removal was performed after embolization of the left lingual artery. There was no evidence of either persistent or recurrent disease 5 years after surgery. The embryologic and anatomic origins of head and neck paragangliomas are reviewed. CONCLUSIONS: An embryologic theory based on the common neural crest origin and migration pathways of both autonomic viscerocranium appended ganglias and paragangliomas is proposed that unifies the topographically heterogeneous group of viscerocranium-appended paragangliomas.
BACKGROUND AND OBJECTIVES: The objective of the present study was to define the location of the most lateral superficial inguinal node lying along the inguinal ligament, through an embryological and anatomotopographical study, in order to rationalize the lateral extension of the groin lymphadenectomy in vulvar cancer. METHODS: Sections of the upper portion of the femoral triangle belonging to three human fetuses, whose crown-rump (CR) length ranged from 70 to 310 mm, corresponding to a developmental age of 11 and 35 weeks, were studied. In addition, for an objective topographical evaluation of the disposition of the superficial inguinal lymph nodes, adult cadavers photographs of dissected Scarpa's triangle, reported in anatomical atlases, were analyzed. RESULTS: Both the embryological investigation and the anatomotopographical evaluation on cadavers photographs demonstrate that the most lateral superficial inguinal lymph node does not rise above the medial margin of the sartorius muscle, nor far lateral to the point where the superficial circumflex iliac vessels cross the inguinal ligament. CONCLUSIONS: On the basis of the present study, the authors believe that the superficial circumflex iliac vessels could represent the lateral surgical landmark, easily detectable, at which the inguinal lymphadenectomy should cease. Therefore, there is no need to extend the lateral excision to the anterior superior iliac spine. Finally, leaving the fatty tissue laterally to these vessels, some lymphatic channels could be preserved, decreasing the incidence and the entity of wound seroma and lymphedema.