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.


Depression Expense Crest Meso 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer Science+Business Media New York 1989

Authors and Affiliations

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

Personalised recommendations