First Somites

8 Days, 1–7 Somites
  • Karl Theiler


The copulation age of this group ranges from 7 days 21 hours to 8 days 21 hours. The seven somite embryo was chosen as the most advanced in this stage because with the formation of the eighth somite, the embryo begins to rotate around its longitudinal axis. In the human, the corresponding age group, as described by Streeter [6], extends from 1 to 12 somites. The number of somites is the most reliable criterion to determine developmental age.


Primitive Streak Dorsal Aorta Oral Plate Trophoblastic Giant Cell Uterine Lumen 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer Science+Business Media New York 1989

Authors and Affiliations

  • Karl Theiler
    • 1
  1. 1.Department of AnatomyUniversity of ZurichZurichSwitzerland

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