A young plant, developing within the seed – in cannabis, an embryo is derived from a fertilized ovule.
An embryo is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell. The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres. The blastomeres (4-cell stage) are arranged as a solid ball that when reaching a certain size, called a morula, (16-cell stage) takes in fluid to create a cavity called a blastocoel. The structure is then termed a blastula, or a blastocyst in mammals.
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| Anatomical terminology |
The mammalian blastocyst hatches before implantating into the endometrial lining of the womb. Once implanted the embryo will continue its development through the next stages of gastrulation, neurulation, and organogenesis. Gastrulation is the formation of the three germ layers that will form all of the different parts of the body. Neurulation forms the nervous system, and organogenesis is the development of all the various tissues and organs of the body.
A newly developing human is typically referred to as an embryo until the ninth week after conception, when it is then referred to as a fetus. In other multicellular organisms, the word "embryo" can be used more broadly to any early developmental or life cycle stage prior to birth or hatching.
English
Alternative forms
- (after the Medieval Latin embryo) embrio [Middle English to the 18th century], embryo [17th century to the present] (singular forms); embryones [17th century to the present], embrio’s [17th–18th centuries], embrioes [17th century], embryos [19th century to the present] (plural forms)
- (after the stem (embryōn-) of the Medieval Latin embryo) embrioun [Middle English], embrion [Middle English to the 18th century], embryon [17th–19th centuries] (singular forms); embrions [17th C.], embryons [17th–19th centuries] (plural forms)
