Interactive CS21 Embryo Model


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        Key to anatomical regions

  • Central nervous system
  • Optic vesicle
  • Otic vesicle
  • Dorsal root ganglia
  • Heart
  • Liver

Movies of CS21 embryos


The movies below show volume renders of OPT models. Images of unstained embryos were captured using autofluorescence with a FITC filter.


N496 46XX
N641 46XY





Painted Anatomical Regions


The movies below show anatomical domains defined in the N496 model. The domains have been manually defined in the OPT models using specialised software and then visualised using commercial rendering packages.

The various domains are: neural tube - orange; eye - dark blue; otic vesicle - yellow; dorsal root ganglia - cyan.


N496 46XX







Carnegie Stage 21 Definition



A 3D model of a human embryo, Carnegie stage 21


Age is approximately 51 postovulatory days

Length is approximately 20 - 26mm

External Features Include: the hands are slightly flexed at the wrists and nearly come together over the cardiac eminence; the feet are also approaching each other and the toes of the two sides sometimes touch; the superficial vascular plexus of the head has spread upward to form a line at somewhat more than half the distance from eye-ear level to the vertex.

O'Rahilly R and Muller F [1987] Developmental Stages in Human Embryos. Carnegie Institute, Washington, Publication no. 637, and O'Rahilly R, Müller F (2010) Developmental stages in human embryos: revised and new measurements. Cells Tissues Organs. 192:73-84. PMID: 20185898.