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.

## Contents

* 1 Stages
* 1.1 Stage 1: 1 days
* 1.2 Stage 2: 3 days
* 1.3 Stage 3: 4 days
* 1.4 Stage 4: 5-6 days
* 1.5 Stage 5 (a-c): 7-12 days
* 1.6 Stage 6: 13-15 days
* 1.7 Stage 7: 15-17 days
* 1.8 Stage 8: 17-19 days
* 1.9 Stage 9: 19-21 days
* 1.10 Stage 10: 21-23 days
* 1.11 Stage 11: 23-26 days
* 1.12 Stage 12: 26-30 days
* 1.13 Stage 13: 28-32 days
* 1.14 Stage 14: 31-35 days
* 1.15 Stage 15: 35-38 days
* 1.16 Stage 16: 36-42 days
* 1.17 Stage 17: 42-44 days
* 1.18 Stage 18: 44-48 days
* 1.19 Stage 19: 48-51 days
* 1.20 Stage 20: 51-53 days
* 1.21 Stage 21: 53-54 days
* 1.22 Stage 22: 54-58 days
* 1.23 Stage 23: 56-60 days
* 2 See also
* 3 External links

## Stages

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

### Stage 1: 1 days

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* fertilization
* polar bodies

### Stage 2: 3 days

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* cleavage
* morula
* compaction

### Stage 3: 4 days

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* blastocyst and blastocoele
* embryonic disk
* trophoblast and embryoblast

### Stage 4: 5-6 days

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* syncytiotrophoblast
* cytotrophoblast
* amniotic ectoderm

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

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

### Stage 6: 13-15 days

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

### Stage 7: 15-17 days

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* gastrulation
* neural plate
* start of hematopoiesis
* notochord

### Stage 8: 17-19 days

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* primitive pit

### Stage 9: 19-21 days

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

### Stage 10: 21-23 days

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

### Stage 11: 23-26 days

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* sinus venosus
* mesonephric duct

### Stage 12: 26-30 days

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* upper limb buds

### Stage 13: 28-32 days

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* septum primum
* foramen primum

### Stage 14: 31-35 days

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* ureteric bud

### Stage 15: 35-38 days

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### Stage 16: 36-42 days

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### Stage 17: 42-44 days

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### Stage 18: 44-48 days

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* septum secundum

### Stage 19: 48-51 days

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### Stage 20: 51-53 days

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### Stage 21: 53-54 days

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### Stage 22: 54-58 days

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### Stage 23: 56-60 days

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## See also

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* Mammalian embryogenesis

## External links

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* 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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