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Developmental Anatomy

Stage 22: Summary

First view Second view

External: The eyelids, which have been thickening gradually, are now rapidly encroaching upon the eyes. The formation of the auricle has progressed noticeably: the tragus and antitragus especially are assuming a more definite form. The superficial vascular plexus of the head extends upward about three-quarters of the way above the eye-ear level. The hands extend further out in front of the body of the embryo, and the fingers of one hand may overlap those of the other.

Lab Manual - Horizon 22 (CC#8394)

First view Second view Third view

  • The eyelids, which have been gradually thickening throughout the period covered by these age groups, are now rapidly encroaching upon the eyeballs.
  • Noticeable progress has been made in the molding of the external ear.
  • The tragus and the antitragus especially are assuming a more definite form.
  • The superficial plexus extends upward about three-fourths the way above the ear-eye level.
  • The hands extend farther out in front of the body of the embryo, and the fingers of one hand overlap those of the other.
  • Ovulation age: 54-56 days.

Stage 22: Animation

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Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.
Published by Carnegie Institution of Washington, Publication 637. 1987.

Stage 22 (PDF 96 KB)

 

QUESTION: How far does the superficial plexus extend at this stage?