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Textbook of Human Embryology. Reviews I Abstracts Edited by LOUIS M. HELLMAN, M.D. Reviews of new books And the Poor Get Children-A Study Sponsored. The Developing Human, 8th itutvimaser.tk, Citation: The developing human: clinically oriented embryology 8th ed. Moore, Keith L. Ebook `Human embryology`: ebooks list of Charles Sedgwick Minot.
Human embryology in the 19th century began by using human embryo samples derived from maternal deaths, abortion, or surgery.
Nothing has been changed in the 21st century, because animal experimental biology developed in the 20th century could not and should not apply to human embryology on its ethical aspect. However, human embryology has progressed little during the last years, with only recently some limited molecular studies on small numbers of human material.
In contrast, recent studies using both nondestructive and destructive imaging techniques on existing collections have allowed many morphological measurements of these embryos using these novel imaging techniques. Here we summarize the historic collections of embryos used in the study of human development, explain the criteria used for developmental staging, show sectioned and reconstructed images from newer three-dimensional 3D imaging in high resolution, and discuss the future directions for the analyses of the human embryo.
During the history of human embryology the establishment and study of key human embryo collections has greatly contributed to our current understanding. In this section we briefly summarize the history of some of these collections, such as the Carnegie Collection, the Kyoto Collection, the Blechschmidt Collection, and the Madrid Collection Table 1.
More online information can be found on existing historic human collections http: The human embryo collections shown in Table 1 , along with other collections, form part of the Digital Embryology Consortium http: Not included in this chapter will be descriptions of the smaller, less described human embryo collections, species comparative embryo collections, or collections that are of nonembryonic material, such as placenta.
An example of a mainly human placenta and early implanted uterus is the Hamilton-Boyd Collection in Cambridge. Note that many anatomy departments hold their own small collections of human material that are not covered here.
A key factor in understanding the developmental morphological changes is the possession of human embryo samples at sequential developmental stages. The following are the major historic collections used in most research and textbook publications that have aided our understanding of human development. Franklin P. Mall — began his human embryo at Johns Hopkins University in the early s; these formed the beginnings of the Carnegie collection. He and Franz Keibel — used these embryos in their textbook Manual of Human Embryology [ 1 , 2 ] and also in the Carnegie Institution of Washington Series Contributions to Embryology beginning in The same staging criteria have been subsequently applied in the organizing of the other major human embryo collections.
These stages will be described in detail from the Kyoto Collection later in this chapter. Reconstructions from histological sections of the collection embryos were the basis of the larger Carnegie models Figure 1 and this technique has also been used in the development of other collection models, as in the Blechschmidt Collection. Mall received his medical degree at the University of Michigan in He traveled to Germany to receive a clinical training, where he met the German embryologist Wilhelm His — This initiated his interest in studying human embryology, and he began collecting human embryos in His collection had reached several hundreds of specimens by the time he returned to the Anatomy department of the Johns Hopkins School of Medicine in Baltimore, Maryland.
He received a Carnegie research grant in and became the first director of the Department of Embryology at the Carnegie Institution of Washington, in Baltimore, MD.
The embryo collection grew at a rate of about specimens a year, donated by clinicians and researchers, and the number of samples reached over 8, by the early s. Researchers at the institute then began the complex task of organizing these embryos into a developmental sequence.
Note that size alone was a difficult criterion due to the variable effects of fixation shrinkage. Internal features were identified histologically from embryos that were serially sectioned, and also formed the basis of hundreds of 3D models and wax-based reconstructions.
George L. Streeter — and Franz J. Heard worked as an embryo modeler; and James D. Didusch as a scientific illustrator. Mall documented his research in a series of papers compiled in the Contributions to Embryology of the Carnegie Institution of Washington, published from to These articles even today are considered the core findings for studying human embryology.
Mall unexpectedly died in and was replaced as director by Streeter. Streeter was then the first to define the 23 Carnegie Stages currently used to classify the developmental stages of the human embryo see Table 2. The collection continued to grow by hundreds of specimens every year and included rare, very young normal specimens.
At the time, induced abortions were illegal in the United States and miscarriages usually resulted from embryo abnormalities. Streeter retired in and George W. Corner —] became the third departmental director. Corner was a former Johns Hopkins researcher who studied the menstrual cycle and identified the ovarian hormone progesterone.
During his direction until , many advances in human reproductive physiology were made and embryology research continued but came to an end with the succeeding director. Relocation of the collection began in to the University of California at Davis Medical School and was completed in At the retirement of the director in the collection was relocated again to its current location at the Walter Reed Army Medical Center in Washington, D.
In , preliminary work began with the current curator on establishing a partnership with the Digital Embryology Consortium to eventually digitize, preserve, and make more widely available this collection. Further details of the embryo collection can be found in earlier publications [ 3 , 4 ] as well as on the web http: Carnegie models located at the Carnegie Collection. Embryos shown in the bottom left-hand corner were laminated from individual layers and then painted.
Originally collected by Charles Minot — , sometimes referred to as the Minot Collection, it now forms part of the larger Carnegie Collection.
By , the collection consisted of histologically sectioned embryos from human and other species Figure 2. Harvard Collection histology slide No. The human embryo collection is named after Erich Blechschmidt — , who directed the Anatomical Institute from until , and consists of two parts: The histology collection is made up of about human embryos that have been cut in a range of anatomical planes into some , serial sections.
In , some of the embryo serial section sets were temporarily incorporated into the Carnegie Collection and assigned Carnegie Nos.
The model collection Figure 3 "Human embryologische Dokumentations sammlung Blechschmidt" forms a permanent exhibition housed at the Centre of Anatomy and consists of 64 large models, generated from to The models are available for viewing upon request and are arranged in perspex cases that allow each model to be observed from all directions.
The models range from selected parts or systems of a specific embryo to whole embryos in surface view. Each model illustrates whole embryo surfaces, some organic systems including a circulatory organ, respiratory organs, a digestive organ, central nerve, and the skeletal system in precision, in addition to the right-side out.
The embryo collection has probably the largest number of excellently preserved specimens of the latter half of the embryonic period covering weeks 5—8 post conception. Detailed documentation on individual specimens of the collection is sparse and some of the specimens are also depicted as color drawings in Blechschmidt [ 5 ]. The high quality and standard of the histology material was achieved by a combination of a "state-of-the-art" embryo collection gynecological practice mechanical curettage or hysterectomy from operations including termination of pregnancy and development of a special fixation procedure.
As a result, the quality of paraffin histological sections mounted on large glass microscope slides is unsurpassed and reveals valuable morphological detail of early organ development in the human embryo. Like many historic collections, even with optimal storage conditions, the slide histology has gradually deteriorated with evaporation of cover glass glue and bleaching of histological stains. Secondly, the large glass microscope slides are delicate and easily damaged during use.
At that time, the only way to preserve for posterity morphological information contained in these specimens consisted in building large-scale polymer plastic reconstruction models.
These models were made from camera-lucida drawings at an intermediate magnification of regularly spaced histological sections [ 6 ]. Using the same series of serial sections several times over, Blechschmidt made reconstructions of the surface anatomy and the morphology of several organ systems of the same embryo, thereby enabling direct comparison of topographical characteristics and their dynamic changes during development, even though the cellular detail detectable at high magnification remained unexplored with this method.
Currently, the way to preserve the collection in its current condition lies with the scanning and digital preservation of the histological material with the Digital Embryology Consortium.
The Orts-Llorca Madrid Collection. Slides of serially sectioned embryos are stored in individual box sets. Photo by Mark Hill. The human embryo histology collection was started in by the Spanish embryologist Francisco Orts-Llorca — and is located at the Embryology Institute of Complutense University of Madrid [ 7 ].
The collection consists of histological serial sections of more than human embryos in thousands of serial sections covering the embryonic and fetal periods Figure 4. The collection includes both normal and abnormal embryos.
The sectioning is in a number of different anatomical planes and includes both normal and abnormal embryonic material. The collection has unfortunately suffered from the rigors of time, handling by many researchers, and fading of histological stains. Klaus V. Hinrichsen was a pupil of Blechschmidt and had the chair of Anatomy and Embryology at the Ruhr University Bochum in The reconstructions have not been attempted from these specimens and many specimens have likewise remained unexplored, to date.
Hideo Nishimura began this collection in and currently has over 44, human embryo specimens. It was further developed and managed by Kohei Shiota for a long period and is currently managed by Shigehito Yamada and all professors in the Department of Anatomy at Kyoto University School of Medicine.
Under the Maternity Protection Law of Japan, induced abortions were legal and in a great majority of cases pregnancies were terminated for social reasons during the first trimester. These provided Nishimura the beginning of the Kyoto collection. In , he formed the Congenital Anomaly Research Center and the collection had now reached over 36, specimens. Currently, this collection is the largest in the world with over 45, specimens Figure 5 and provides a key resource for international embryology researchers.
An important characteristic of the collection is inclusion of both normal and many abnormal embryos with severe malformations [ 10 ], including holoprosencephaly.
This in turn leads to the characteristically abnormal facial development. Note that the estimation of embryonic frequency may be lower than the actual prevalence, as milder forms of holoprosencephaly also exist, but are more difficult to diagnose [12, 13].
Another unique feature of the Kyoto Collection is the associated maternal epidemiological data and detailed clinical information on the pregnancies that were collected with each specimen. The epidemiological data has been used for statistical analysis to determine potential causative links between maternal factors and congenital anomalies [ 14 ].
The collection has more recently been analyzed using several new advanced imaging technologies that allow 3D embryo imaging and subsequent generation of digital models. Firstly, magnetic resonance microscopy MRM, see 4.
Secondly, episcopic fluorescence image capture EFIC and phase-contrast X-ray computed tomography pCT techniques have also been applied to these embryos 18, 22, see 4. The current curator, Shigehito Yamada, has now commenced the lengthy process of digitizing all histological sections within this collection and is also a contributing partner in the new digital consortium.
The Kyoto Collection is currently one of the largest and best catalogued human embryo collections, containing approximately equal numbers of both normal and abnormal specimens. The collection is also divided into whole wet specimens see sub-heading 4. More recently, the current curator has digitized and made available online sections from some of the normal embryos in the collection http: Kyoto Collection of human embryos. Image shows embryo storage, fixed wet whole embryos, histological collection, and digitization process.
This huge collection of comparative embryonic material from vertebrate species consists of 3, wet specimens and 80, histological sections from many species including human [ 23 ]. There is also a significant collection of photographic material and documentation available. The collection is made available for researchers upon request. With permission, collection slides can be photographed and used for research purposes.
The Human Developmental Biology Resource http: There are also histological sections hematoxylin and eosin stained from human embryos covering these stages of development.
Classification into developmental stages is necessary to accurately describe prenatal growth. Embryonic staging of animals was introduced at the end of the 19th century [ 25 ], and was first applied to human embryology by Mall [ 26 ]. The Carnegie stage is commonly known as a staging scheme which remains widely used today.
Embryonic age days based on developmental stages CS of human embryos, according to various authors. At fertilization, the oocyte completes meiosis II, forming the female pronucleus.
The spermatozoa nucleus in the oocyte cytoplasm decompresses, forming the male pronuclei. These two pronuclei fuse to form the first diploid cell, the zygote. The first mitosis occurs during the 24 h after zygote formation. The zygote forms two blastomeres.
Mitosis of these blastomeres forms a solid ball of 16 cells, then 32 cells, still enclosed by the zona pellucida. This cleavage stage divides the large zygote cytoplasm into sequentially smaller cells. Cell division continues after the 32 cell stage occurring more rapidly at the surface and slower in the center cells. This and directional fluid transfer leads to a cavity, the blastocoel, in the conceptus. The surface cells form an outer squamous trophoblast layer linked by both tight and gap junctions.
The larger inner cells form the inner cell mass or embryoblast. The blastocyst hatches from the zone pellucida, still floating in uterine secretions of the secretory phase of the menstrual cycle. The surface trophoblast cells can now initially adhere to the endometrial epithelium at the site of implantation. The trophoblast cells proliferate and differentiate into two layers.
The outer cells fusing to form syncytiotrophoblasts, the inner close remain as single cells, cytotrophoblasts. This stage was originally divided into three a, b, and c substages based on trophoblast differentiation status before outgrowth villi appears. Trophoblast cells extend into the maternal uterine stroma decidua forming chorionic villi.
The extra-embryonic mesoderm arises, lining the conceptus cavity and forming the chorionic cavity. Three separate cavities or extra-embryonic coeloms form outside the embryonic disc: Toward the end of this stage, the primitive streak appears on the embryonic disc; this is the site of gastrulation.
Gastrulation occurs here forming endoderm and mesoderm that spread laterally and rostrally from the primitive streak. Above the primitive node, cranially, the notochordal process develops in the mesodermal layer.
The length of this process increases from 0. The embryonic disc increases in size and the amniotic cavity enlarges over the yolk sac.
The embryonic disc is pyriform, tapering caudally, and now has cranio-caudal axis, measured from this stage onward by crown-rump length CRL.
The stage shows three key features: The notochordal canal is marked by the cavity extending from the primitive pit into the notochordal process. The floor of the canal is lost to form a transient passage, neurenteric canal, between the amniotic cavity and the yolk sac.
The notochord process will differentiate into the notochord or axial mesoderm. The remainder of new mesoderm layer has not yet segmented and is called the presomitic stage. The mesoderm either side of the notochord now segments into paired somites. Segmentation of paraxial mesoderm only occurs at the level of the trunk, not the head, and proceeds in a cranial-caudal direction.
Note that the sequential appearance of somite pairs can also be used as a criterion to stage the embryo. The embryonic disc resembles a shoe-sole, with the broad neural plate in the ectoderm layer positioned in the cranial region.
The mid-line neural plate begins to fold forming a neural groove. Somitogenesis continues increasing from 4 to 12 somite pairs. The neural groove continues to fold bringing the neural plate edges together to commence fusing. This fusion occurs in both cranial and caudal directions and at several sites. In the head region, the optic sulcus and first pharyngeal branchial arch appear. In the underlying trunk region mesoderm the cardiac tube appears.
Somitogenesis continues increasing from 13 to 20 somite pairs. The neural groove has formed an open-ended neural tube, and the upper head end anterior, cranial or rostral opening neuropore commences to close. Optic evagination is produced at the optic sulcus and the optic ventricle is continuous with that of the forebrain. The cardiac tube has formed a loop, with a sinus venosus region appearing. The second pharyngeal arch is visible.
A ventral indentation stomodeum is present at the level of the first arch. The floor of the stomodeum forms the oral membrane buccopharyngeal that commences to degenerate. Dorsally at the level of the second arch, paired otic placodes fold inward to form the otic vesicles.
Somitogenesis continues with 21—29 somite pairs. The posterior caudal neuropore is starting to close or is closed. Three of the pharyngeal arches are now clearly visible. The upper limb buds appear, initially as lateral swellings at the level of the heart. The book proves nothing new, gives no new information, and, unfortunately, treats the psychological problems in a very superficial manner. Textbook of Human Embryology. Springfield, Ill.
In order to produce a textbook of embryology for the medical student that will not only provide a knowledge of developmental anatomy but which would also provide some insight into the clinical manifestations of the field of embryology, Professor Harrison has begun with the chicken instead of the egg, and starts by reviewing the anatomy and physiology of the adult male and female reproductive systems.
Following in a logical manner, he proceeds through fertilization, nidation, and early embryo growth. By limiting the number of photomicrographs and by utilizing simplified line drawings he presents a complete summary of the early developmental phases. There is an excellent chapter on the development of the placenta with mention of its role in such clinical entities as placenta previa and Rh sensitization and a short summary of its hormone functions and relationships.
As soon as the embryo has reached the somite and limb bud stage, the organism as a whole is abandoned, and each organ system is taken up individually and is followed through its development with clinical relationships brought out whenever possible.
The details of much of the cellular morphology is left out in favor of emphasis on functional development. Accordingly, there is little or no mention of the complex and technical dcvclopments of chemical embryology which belongs more properly in the texts designed for specialized workers in this field.