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.

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]

• fertilization
• polar bodies

Stage 2: 3 days[edit | edit source]

• cleavage
• morula
• compaction

Stage 3: 4 days[edit | edit source]

• blastocyst and blastocoele
• embryonic disk
• trophoblast and embryoblast

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

• syncytiotrophoblast
• cytotrophoblast
• amniotic ectoderm

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

• implantation
• bilaminar germ disk
• primary yolk sac
• amniotic cavity

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

• primitive streak
• primitive groove
• chorionic villi
• secondary yolk sac

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

• gastrulation
• neural plate
• start of hematopoiesis
• notochord

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

• primitive pit

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

• neural groove
• neural folds
• septum transversum
• placode
• early heart

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

• pharyngeal arches #1 and #2
• cardiac loop
• intermediate mesoderm

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

• sinus venosus
• mesonephric duct

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

• upper limb buds

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

• septum primum
• foramen primum

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

• ureteric bud

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]

• septum secundum

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]

• Mammalian embryogenesis

External links[edit | edit source]

• Template:EmbryologySwiss
• Template:EmbryologyUNSW
• Photos at unsw.edu.au
• 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

Template:Embryology

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