- Carnegie stages
In
embryology , Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of thevertebrate 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. It only covers the first 60 days of development; at that point the term
embryo is usually replaced with the termfetus .It was based on work by Streeter (1942) and O'Rahilly and Müller (1987). The name "Carnegie stages" comes from the
Carnegie Institute .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 organism s indevelopmental biology , such as theHamburger-Hamilton stages in the chick.tages
Days are approximate, and reflect the days since the last
ovulation beforepregnancy ("Postovulatory age").tage 1: 1 days
*
fertilization
*polar bodies tage 2: 2-3 days
* cleavage
*morula
* compactiontage 3: 4-5 days
*
blastocyst andblastocoele
*embryonic disk
*trophoblast andembryoblast tage 4: 6 days
*
syncytiotrophoblast
*cytotrophoblast
* amnioticectoderm tage 5 (a-c): 7-12 days
*
implantation
*bilaminar germ disk
* primaryyolk sac
*amniotic cavity tage 6: ca 17 days
*
primitive streak
*primitive groove
*chorionic villi
* secondaryyolk sac tage 7: ca 19 days
*
gastrulation
*neural plate
* start ofhematopoiesis
*notochord tage 8: ca 23 days
*
primitive pit tage 9: ca 25 days
*
neural groove
*neural folds
*septum transversum
*placode
* earlyheart tage 10: ca 28 days
*
pharyngeal arches #1 and #2
*cardiac loop
*intermediate mesoderm tage 11: ca 29 days
*
sinus venosus
*mesonephric duct tage 12: ca 30 days
* upper
limb buds tage 13: ca 32 days
*
septum primum
*foramen primum tage 14: ca 33 days
*
ureteric bud tage 15: ca 36 days
tage 16: ca 39 days
tage 17: ca 41 days
tage 18: ca 44 days
*
septum secundum tage 19: ca 46 days
tage 20: ca 49 days
tage 21: ca 51days
tage 22: ca 53 days
tage 23: ca 56 days
ee also
*
Mammalian embryogenesis External links
*
*
* [http://embryology.med.unsw.edu.au/wwwhuman/Stages/Images/Cst800.jpgPhotos at unsw.edu.au]
* [http://embryo.soad.umich.edu/carnStages/carnStages.html Overview at umich.edu]
* [http://virtualhumanembryo.lsuhsc.edu/HEIRLOOM/Stages/HEP_StagesFS.htm Details on stages at lsuhsc.edu]
* [http://genex.hgu.mrc.ac.uk/Databases/HumanAnatomy/new/ List of structures by week, at mrc.ac.uk]
* [http://www.visembryo.com/baby/index.html Diagrams at actual size at Visible Embryo]
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