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| Week 3 - Human Embryo Stages and Events (GA week 5)
|
| Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
|
| Day
|
Stage
|
Event
|
| 15
|
|
|
| 16
|
Stage 7
|
Gastrulation primitive node (Hensen's node, primitive knot) The small circular region located at the cranial end of the primitive streak, where gastrulation occurs, and is a controller of this process. The process establishes the 3 germ cell layers: Endoderm, Mesoderm and Ectoderm. The second role is to act as an initial generator of the left-right (L-R) body axis.
|
| 17
|
|
|
| 18
|
Stage 8
|
Neural - neurogenesis, neural groove and folds are first seen
|
| 19
|
|
|
| 20
|
Stage 9
|
Musculoskeletal - somitogenesis, first somites form and continue to be added in sequence caudally (1 - 3 somite pairs).
Neural - the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open
Neural Crest - mesencephalic neural crest is visible[1]
|
| 21
|
|
Heart - cardiogenesis, week 3 begins as paired heart tubes.
|
| Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
|
References
- ↑ <pubmed>17848161</pubmed>
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