Talk:Rat Development Stages

From Embryology
Standard Stages (Witschi)
Carnegie (approx)
Age (days)
Size (mm)
Identification of Stages
Cleavage and Blastula
1 1 1 0.07 1 cell (in oviduct)
2 2 0.08 x 0.06 2 cells (in oviduct)
3 3 0.08 x 0.05 4 cells (in oviduct)
4 3.25 8-12 cells (in oviduct)
5 2 3.5 0.08 x 0.04 Morula (in uterus)
6 4 (0.08 x 0.03) Early blastocyst (in uterus)
7 3 5 (0.12 x 0.05) Free blastocyst (in uterus)
Gastrula
8 4 6 (0.28 x 0.07) Implanting blastocyst, with trophoblastic cone and inner cell mass; outgrowth of endoderm (hypoblast)
9 6.75 Diplotrophoblast; inner cell mass (pendant), covered with endoderm
10 5 7.25 (0.3 x 0.1) Near complete implantation; pendant begins differentiation into embryonic and extra-embryonic parts
11 7.75 (0.5 x 0.1) Completion of implantation; primary amniotic cyst; ectoplacental cone
Primitive Streak
12 6 8.5 (1.04 x 0.26) Connecting ectochorionic and amniotic cavities; rudiments of amniotic folds; primitive streak; start of 3rd layer formation; blastemas of heart and pericardium
Neurula
13 7 9 1.0 Presomite neurula; fusion of chorio-amniotic folds, chorio-amniotic stalk; neural plate; embryo bent dorsally; bud of allantoic stalk
14 9.5 1.5 Somites 1-4 (occipital); pendant with 3 cavities: ectochorionic cyst, exocoelom, and amniotic cavity; ectochorionic cyst collapsing; allantoic stalk projects into exocoelom; embryo bent dorsally