Template:Week 3 Embryo Stages and Events table
From Embryology
Week 3 - Human Embryo Stages and Events (GA week 5) | ||
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Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9 | ||
Event | ||
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. | |
Stage 8 | Neural - neurogenesis, neural groove and folds are first seen | |
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] | |
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
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