Paper - Description of a Human Embryo of Twenty-two paired Somites

A Gurgis

<pubmed>17104111</pubmed>| PMC1249865

Historic Embryology

This is a slightly edited version of the original 1926 paper published in Journal of Anatomy. The full paper is still available as a PDF document through PubMed Central.

Historic Disclaimer - information about historic embryology pages
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

Carnegie Staging Comparison: A 22 somite stage embryo would be similar to a Carnegie stage 12 (26 - 30 days), caudal neuropore closes, Somite Number 21-29.

Clinical History and Age

A human chorionic vesicle was kindly presented to me in November, 1923, by DrMahfouz Bey, Professor of Midwifery at Kasr-el-Eini Hospital,Cairo. He gave me the following short history without dates: "Copulation took place 2weeks after menstruation. Abortion occurred 5 days after the succeeding menstruation was due; haemorrhage two days before the abortion.

Historic Disclaimer - information about historic embryology pages
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

The information below was not part of the above original historic article.

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Carnegie Stage Table

Weeks shown in the table below are embryonic post ovulation age, for clinical Gestational Age (GA) measured from last menstrual period, add 2 weeks.

Stage	Days (approx)	Size (mm)	Images (not to scale)	Events
1	1 (week 1)	0.1 - 0.15		fertilized oocyte, zygote, pronuclei
2	2 - 3	0.1 - 0.2		morula cell division with reduction in cytoplasmic volume, blastocyst 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, gastrulation
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		Somitogenesis 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 37 weeks)