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UNSW Embryology

Carnegie Stage table

© Dr Mark Hill (2009)

Acknowledgements

Introduction

This current page has images of Carnegie stage 1 to 23 of Human embryonic development organized as a table showing dates and features for each stage.

Stages are based on the external and/or internal morphological development of the embryo, and are not directly dependent on either age or size. The human embryonic period proper is divided into 23 Carnegie stages. Criteria beyond morphological features include age in days, number of somites present, and embryonic length. (about Carnegie) Note that images are not to scale.

Related Stage pages: Carnegie Stage page with larger images of each stage. Week by week timeline of human development showing key features with links to other resources. Carnegie Stage Posters poster versions (in preparation) of the human carnegie stages.

Clicking on the small image will open a large image version of that stage.

To see the various staging systems for each species look at the Embryo Staging Systems references.

Carnegie Stage Table

Stage

Days (approx)

Size (mm)

Images
(not to scale, click image to see original)

Events

1

1

(week 1)

0.1-0.15

fertilized oocyte, pronuclei

2

2 - 3

0.1-0.2

cell division with reduction in cytoplasmic volume, formation of inner and outer cell mass

3

4 - 5

0.1-0.2

loss of zona pellucida, free blastocyst

4

5 - 6

0.1-0.2

attaching blastocyst

5

7 - 12
(week 2)

0.1-0.2

implantation

6

13 - 15

0.2

extraembryonic mesoderm, primitive streak

7

15 - 17

(week 3)

0.4

gastrulation, notochordal process

8

17 - 19

1.0 - 1.5

primitive pit, notochordal canal

9

19 - 21

1.5 - 2.5

Somite Number 1 - 3

neural folds, cardiac primordium, head fold

10

22 - 23

(week 4)

2 - 3.5

Somite Number 4 - 12

neural fold fuses

11

23 - 26

2.5 - 4.5

Somite Number 13 - 20

rostral neuropore closes

12

26 - 30

3 - 5

Somite Number 21 - 29

caudal neuropore closes

13

28 - 32

(week 5)

4 - 6

Somite Number 30

leg buds, lens placode, pharyngeal arches

Stage 13/14 shown in serial embryo sections series of Embryology Program

14

31 - 35

5 - 7

lens pit, optic cup

15

35 - 38

7 - 9

lens vesicle, nasal pit, hand plate

16

37 - 42

(week 6)

8 - 11

nasal pits moved ventrally, auricular hillocks, foot plate

17

42 - 44

11 - 14

finger rays

18

44 - 48

(week 7)

13 - 17

ossification commences

19

48 - 51

16 - 18

straightening of trunk

20

51 - 53

(week 8)

18 - 22

upper limbs longer and bent at elbow

21

53 - 54

22 - 24

hands and feet turned inward

Stage 22 shown in serial embryo sections series of Embryology Program

22

54 - 56

23 - 28

eyelids, external ears

23

56 - 60

27 - 31

rounded head, body and limbs

Following this stage Fetal Development occurs until birth (approx 40 weeks)

(Source: Rothenburger and Gay, 1995. and others)

References

Search Pubmed Now: Human[TITL]+embryo[WORD]+stages[WORD]

UNSW Embryology ISBN: 978 0 7334 2609 4

UNSW CRICOS Provider Code No. 00098G