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Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus .
Evolutionary embryology is the expansion of comparative embryology by the ideas of Charles Darwin. Similarly to Karl Ernst von Baer 's principles that explained why many species often appear similar to one another in early developmental stages, Darwin argued that the relationship between groups can be determined based upon common embryonic and ...
In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.. The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos.
Comparative vertebrate embryology. The embryonic disc becomes oval and then pear-shaped, the wider end being directed forward. Towards the narrow, posterior end, an opaque primitive streak , is formed and extends along the middle of the disc for about half of its length; at the anterior end of the streak there is a knob-like thickening termed ...
The face and neck development of the human embryo refers to the development of the structures from the third to eighth week that give rise to the future head and neck.They consist of three layers, the ectoderm, mesoderm and endoderm, which form the mesenchyme (derived form the lateral plate mesoderm and paraxial mesoderm), neural crest and neural placodes (from the ectoderm). [1]
The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation.Due to its large overlap with development of the urinary system, the two systems are typically described together as the genitourinary system.
The development of the nervous system in humans, or neural development, or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience.These describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development, and continues to develop postnatally.
Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth.During organogenesis, the three germ layers formed from gastrulation (the ectoderm, endoderm, and mesoderm) form the internal organs of the organism.