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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 .
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]
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.
Research utilizing cybrid embryos has been hotly contested due to the ethical implications of further cybrid research. In 2008, the House of Lords passed the Human Fertilisation and Embryology Act 2008, which allows the creation of mixed human-animal embryos for medical purposes only.
First attested in English in the mid-14c., the word embryon derives from Medieval Latin embryo, itself from Greek ἔμβρυον (embruon), lit. "young one", [1] which is the neuter of ἔμβρυος (embruos), lit. "growing in", [2] from ἐν (en), "in" [3] and βρύω (bruō), "swell, be full"; [4] the proper Latinized form of the Greek term would be embryum.
The main processes involved in the embryonic development of animals are: tissue patterning (via regional specification and patterned cell differentiation); tissue growth; and tissue morphogenesis.
The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (), goes through stages resembling or representing successive adult stages in the evolution of the ...
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.