Template:Week 3 Embryo Stages and Events table

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
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