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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.


Stages[edit | edit source]

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

Stage 1: 1 days[edit | edit source]

Stage 2: 3 days[edit | edit source]

Stage 3: 4 days[edit | edit source]

Stage 4: 5-6 days[edit | edit source]

Stage 5 (a-c): 7-12 days[edit | edit source]

Stage 6: 13-15 days[edit | edit source]

Stage 7: 15-17 days[edit | edit source]

Stage 8: 17-19 days[edit | edit source]

Stage 9: 19-21 days[edit | edit source]

Stage 10: 21-23 days[edit | edit source]

Stage 11: 23-26 days[edit | edit source]

Stage 12: 26-30 days[edit | edit source]

Stage 13: 28-32 days[edit | edit source]

Stage 14: 31-35 days[edit | edit source]

Stage 15: 35-38 days[edit | edit source]

Stage 16: 36-42 days[edit | edit source]

Stage 17: 42-44 days[edit | edit source]

Stage 18: 44-48 days[edit | edit source]

Stage 19: 48-51 days[edit | edit source]

Stage 20: 51-53 days[edit | edit source]

Stage 21: 53-54 days[edit | edit source]

Stage 22: 54-58 days[edit | edit source]

Stage 23: 56-60 days[edit | edit source]

See also[edit | edit source]

External links[edit | edit source]

Mammalian development of embryo and development and fetus (some dates are approximate - see Carnegie stages) - edit

Week 1: Zygote | Morula | Blastula/Blastomere/Blastosphere | Archenteron/Primitive streak | Blastopore | Allantois | Trophoblast (Cytotrophoblast | Syncytiotrophoblast | Gestational sac)

Week 2: Yolk sac | Vitelline duct | Bilaminar disc

Week 3: Hensen's node | Gastrula/Gastrulation | Trilaminar embryo Branchial arch (1st) | Branchial pouch | Meckel's cartilage | Somite/Somitomere | Germ layer (Ectoderm, Endoderm, Mesoderm, Chordamesoderm, Paraxial mesoderm, Intermediate mesoderm, Lateral plate mesoderm)

Histogenesis and Organogenesis

Circulatory system: Primitive atrium | Primitive ventricle | Bulbus cordis | Truncus arteriosus | Ostium primum | Foramen ovale | Ductus venosus | Ductus arteriosus | Aortic arches | Septum primum | Septum secundum | Cardinal veins

Nervous system: Neural development/Neurulation | Neurula | Neural folds | Neural groove | Neural tube | Neural crest | Neuromere (Rhombomere) | Notochord | Optic vesicles | Optic stalk | Optic cup

Digestive system: Foregut | Midgut | Hindgut | Proctodeum | Rathke's pouch | Septum transversum

Urinary/Reproductive system: Urogenital folds | Urethral groove | Urogenital sinus | Kidney development (Pronephros | Mesonephros | Ureteric bud | Metanephric blastema) | Fetal genital development (Wolffian duct | Müllerian duct | Gubernaculum | Labioscrotal folds)

Glands: Thyroglossal duct

Uterine support: Placenta | Umbilical cord (Umbilical artery, Umbilical vein, Wharton's jelly) | Amniotic sac (Amnion, Chorion)

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