Carnegie stages
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. In the human being only the first 60 days of development are covered; at that point the term embryo is usually replaced with the term fetus.
It was based on work by Streeter (1942) and O'Rahilly and Müller (1987). The name "Carnegie stages" comes from the Carnegie Institution of Washington.
While the Carnegie stages provide a universal system for staging and comparing the embryonic development of most vertebrates, other systems are occasionally used for the common model organisms in developmental biology, such as the Hamburger–Hamilton stages in the chick.
Stages
Days are approximate, and reflect the days since the last ovulation before pregnancy ("Postovulatory age").
Stage 1: 1 days
Stage 2: 2-3 days
Stage 3: 4-5 days
- blastocyst and blastocoele
- trophoblast and embryoblast
Stage 4: 6 days
- syncytiotrophoblast
- cytotrophoblast
- amniotic ectoderm
Stage 5 (a-c): 7-12 days
Stage 6: ca 17 days
Stage 7: ca 19 days
- gastrulation
- neural plate
- start of hematopoiesis
- notochord
Stage 8: ca 23 days
Stage 9: ca 25 days
Stage 10: ca 28 days
- pharyngeal arches #1 and #2
- cardiac loop
- intermediate mesoderm
Stage 11: ca 29 days
Stage 12: ca 30 days
- upper limb buds
Stage 13: ca 32 days
Stage 14: ca 33 days
Stage 16: ca 39 days
- lower limb buds
Stage 17: ca 41 days
- implementation embryo in posterior uterus wall
Stage 18: ca 44 days
See also
External links
- Swiss embryology (from UL, UB, and UF) iperiodembry/carnegie02
- UNSW Embryology - Carnegie Stages
- Overview at umich.edu
- Details on stages at lsuhsc.edu
- List of structures by week, at mrc.ac.uk
- Diagrams at actual size at Visible Embryo
References
- Hill, M.A. (2016) Embryology Carnegie Stages. Retrieved August 19, 2016, from https://embryology.med.unsw.edu.au/embryology/index.php/Carnegie_Stages