Carnegie stage table

Carnegie Stage Table

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 40 weeks)