An embryo is the early stage of development of a multicellular organism. Each embryo starts development as a zygote, a single cell resulting from the fusion of gametes. A newly developing human is typically referred to as an embryo until the ninth week after conception. In animals that hatch from an egg, such as birds, a young animal is typically no longer referred to an embryo once it has hatched.
About Embryo in brief
An embryo is the early stage of development of a multicellular organism. Each embryo starts development as a zygote, a single cell resulting from the fusion of gametes. A newly developing human is typically referred to as an embryo until the ninth week after conception. In animals that hatch from an egg, such as birds, a young animal is typically no longer referred to an embryo once it has hatched. In human development, the term fetus is used instead of embryo after the 9th week of conception. The word embryon derives from Medieval Latin embryo, itself from Greek ἔμβρυον, lit. ‘growing in’. However, the word ‘embryo’ can be used more broadly to any early developmental or life cycle stage prior to birth or hatching. The embryonic period varies from species to species. In zebrafish, embryonic development is considered finished when the cleithrum becomes visible. However the extent of growth and development after birth or exit from the parent is no longer considered an embryo. In birds, an egg that hatches from a vivapous animals is typically called vivarapous, which means ‘out of the womb’ or ‘unhatched’ The word ’ embryo’ is also used to refer to a developing embryo that has not yet hatched from the egg or is not considered to be an embryo at all.
It is also the name given to a stage in the life cycle that begins just after fertilization and continues through the formation of body structures such as tissues and organs. The process of embryonic development can be divided into four stages, often divided into cleavage, blastula, gastrulation, and organogenesis. Cleavage is the period of rapid mitotic cell divisions that occur following fertilization. The embryo’s cells continue to divide and increase in number, while molecules within the cells such as RNAs and proteins actively promote key developmental processes such as gene expression, cell fate specification, and polarity. Gastrulation is the next phase of embryonic. development, and involves the development of two or more layers of cells.
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This page is based on the article Embryo published in Wikipedia (as of Dec. 03, 2020) and was automatically summarized using artificial intelligence.
