AskDefine | Define embryos

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English

Noun

embryos
  1. Plural of embryo

Extensive Definition

An embryo (from Greek: , plural , lit. "that which grows," from en- "in" + bryein "to swell, be full") is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination. In humans, it is called an embryo from the moment of fertilisation until the end of the 8th week, whereafter it is instead called a fetus.

Development

The development of the embryo is called embryogenesis. In organisms that reproduce sexually, once a sperm fertilizes an egg cell, the result is a cell called the zygote that has all the DNA of two parents. The resulting embryo derives 50 percent of its genetic makeup from each parent. In plants, animals, and some protists, the zygote will begin to divide by mitosis to produce a multicellular organism. The result of this process is an embryo.

In animals

In animals, the development of the zygote into an embryo proceeds through specific recognizable stages of blastula, gastrula, and organogenesis. The blastula stage typically features a fluid-filled cavity, the blastocoel, surrounded by a sphere or sheet of cells, also called blastomeres.
  • Plants: In botany, a seed plant embryo is part of a seed, consisting of precursor tissues for the leaves, stem (see hypocotyl), and root (see radicle), as well as one or more cotyledons. Once the embryo begins to germinate — grow out from the seed — it is called a seedling. Plants that do not produce seeds, but do produce an embryo, include the bryophytes and ferns. In these plants, the embryo is a young plant that grows attached to a parental gametophyte.
  • Animals: The embryo of a placental mammal is defined as the organism between the first division of the zygote (a fertilized ovum) until it becomes a fetus. In humans, the embryo is defined as the product of conception from implantation in the uterus through the eighth week of development. An embryo is called a fetus at a more advanced stage of development and up until birth or hatching. In humans, this is from the eighth week of gestation.
embryos in Arabic: جنين
embryos in Catalan: Embrió
embryos in Czech: Embryo
embryos in Danish: Embryon
embryos in German: Embryo
embryos in Estonian: Embrüo
embryos in Spanish: Embrión
embryos in Esperanto: Embrio
embryos in Persian: جنین
embryos in French: Embryon
embryos in Galician: Embrión
embryos in Ido: Embriono
embryos in Indonesian: Embrio
embryos in Italian: Embrione
embryos in Luxembourgish: Embryo
embryos in Lithuanian: Gemalas
embryos in Dutch: Embryo
embryos in Japanese: 胚
embryos in Norwegian: Embryo
embryos in Occitan (post 1500): Embrion
embryos in Polish: Embrion
embryos in Portuguese: Embrião
embryos in Russian: Эмбрион
embryos in Simple English: Embryo
embryos in Slovak: Embryo
embryos in Slovenian: Zarodek
embryos in Serbo-Croatian: Zametak
embryos in Serbian: Ембрион
embryos in Finnish: Alkio
embryos in Swedish: Embryo
embryos in Turkish: Embriyo
embryos in Ukrainian: Ембріон
embryos in Urdu: جنین
embryos in Chinese: 胚胎
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