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Stage 21 embryos have a greatest length of 20 to 26.4 mm and an estimated post-fertilization age of approximately 49 to 52 days. At this stage the fingers become more elongated and the hands and feet approach each other. For the first time the cortical plate is present in the wall of the cerebral vesicle (hemisphere). The stage is represented by Carnegie embryo #4090 that has a greatest length of 22.2 mm (after fixation). This female specimen is considered to be early within the stage.


New structures include brachioradialis muscle, cricoid cartilage, ethmoid, patella, submandibular gland.

Section 89

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