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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. It only covers the first 60 days of development; 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 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 organisms in developmental biology, such as the Hamburger-Hamilton stages in the chick.

Additional recommended knowledge

Stages

Days are approximate, and reflect the days since the last ovulation before pregnancy ("Postovulatory age").

Stage 1: 1 days

fertilization
polar bodies

Stage 2: 3 days

cleavage
morula
compaction

Stage 3: 4 days

blastocyst and blastocoele
embryonic disk
trophoblast and embryoblast

Stage 4: 5-6 days

syncytiotrophoblast
cytotrophoblast
amniotic ectoderm

Stage 5 (a-c): 7-12 days

implantation
bilaminar germ disk
primary yolk sac
amniotic cavity

Stage 6: 13-15 days

primitive streak
primitive groove
chorionic villi
secondary yolk sac

Stage 7: 15-17 days

gastrulation
neural plate
start of hematopoiesis
notochord

Stage 8: 17-19 days

primitive pit

Stage 9: 19-21 days

neural groove
neural folds
septum transversum
placode
early heart

Stage 10: 21-23 days

pharyngeal arches #1 and #2
cardiac loop
intermediate mesoderm

Stage 11: 23-26 days

Stage 12: 26-30 days

upper limb buds

Stage 13: 28-32 days

septum primum
foramen primum

Stage 14: 31-35 days

ureteric bud

Stage 15: 35-38 days

Stage 16: 36-42 days

Stage 17: 42-44 days

Stage 18: 44-48 days

septum secundum

Stage 19: 48-51 days

Stage 20: 51-53 days

Stage 21: 53-54 days

Stage 22: 54-58 days

Stage 23: 56-60 days

v • d • e Developmental biology > Human embryogenesis (development of embryo) and development of fetus (some dates are approximate - see Carnegie stages and a timeline)
Week 1	Fertilization - Egg activation - Zygote - Cleavage - Morula - Blastula (Blastomere) - Blastocyst - Inner cell mass
Week 2	Bilaminar disc (Hypoblast, Epiblast)
Week 3 (Trilaminar embryo, germ layers)	Archenteron/Primitive streak (Primitive pit, Primitive knot/Blastopore, Primitive groove) - Gastrula/Gastrulation - Regional specification Ectoderm: Surface ectoderm - Neuroectoderm - Somatopleure - Neurulation - Neural crest Endoderm: Splanchnopleure Mesoderm: Chorda- - Paraxial (Somite/Somitomere/Sclerotome/Myotome/Dermatome) - Intermediate - Lateral plate (Intraembryonic coelom, Splanchnopleure/Somatopleure)
Extraembryonic/uterus	Trophoblast (Cytotrophoblast, Syncytiotrophoblast) Blastocoele - Yolk sack/exocoelomic cavity - Heuser's membrane - Extraembryonic coelom - Vitelline duct Umbilical cord (Umbilical artery, Umbilical vein, Wharton's jelly) - Allantois Placenta - Decidua (Decidual cells) - Chorionic villi/Intervillous space - Gestational sac (Amnion/Amniotic sac/Amniotic cavity, Chorion)
Histogenesis	Programmed cell death - Stem cells - Germ line development
Organogenesis	Limb development: Limb bud - Apical ectodermal ridge/AER - Eye development - Cutaneous structure development - Heart development - Development of the urinary and reproductive organs

Category: Embryology

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Carnegie_stages". A list of authors is available in Wikipedia.