Template:Human Embryo - Biological definition 2006

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Human Embryo - Biological definition  
Modern Definition

The following biological definition comes from the Australian National Health and Medical Research Council (NHMRC) discussion paper (2006).

"human embryo means a discrete entity that has arisen from either:
(a) the first mitotic division when fertilisation of a human oocyte by a human sperm is complete; or
(b) any other process that initiates organised development of a biological entity with a human nuclear genome or altered human nuclear genome that has the potential to develop up to, or beyond, the stage at which the primitive streak appears;
and has not yet reached 8 weeks of development since the first mitotic division."

This definition was also published later by the same group in 2007.[1]

Historical Definition

"The distinction between the embryonic and the fetal periods at 8 postovulatory weeks has proved valuable. It is based primarily on the probability that more than 90 percent of the more than 4,500 named structures of the adult body have appeared by that time."[2][3]

Links: Embryonic Development | Fertilization | NHMRC paper PDF
  1. Findlay JK, Gear ML, Illingworth PJ, Junk SM, Kay G, Mackerras AH, Pope A, Rothenfluh HS & Wilton L. (2007). Human embryo: a biological definition. Hum. Reprod. , 22, 905-11. PMID: 17178746 DOI.
  2. O'Rahilly R. 1979. Early human development and the chief sources of information on staged human embryos. Europ. J. Obstet. Gynec. Reprod. Biol., 9, 273-280. PMID 400868
  3. O'Rahilly R. and Müller F. Developmental Stages in Human Embryos. Contrib. Embryol., Carnegie Inst. Wash. 637 (1987).