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Stage 10 embryos have a greatest length of 1.5 to 3.6 mm and an estimated postfertilization age of 28 to 30 days. There are 4 to 12 pairs of somites along the body axis. The neural tube has begun to form which exhibits rostral and caudal neuropores. The five major subdivisions of the brain can be identified in the neural folds. The optic sulcus is present with a chiasmatic plate in the midline. Presumptive left and right atria and ventricles of the heart can be identified by their relative locations.


New structures include facio-vestibulocochlear neural crest (CN VII and CN VIII), laryngotracheal sulcus, neural tube, neuroectoderm, rostral neuropore, thyroid gland.

Section 189

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Dorsal 2

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