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Stage 23 embryos have a greatest length of 23 to 32.2 mm and an estimated postfertilization age of 53 to 58 days. Over 90% of the more than 4,500 named structures in the adult body are present. The limbs are longer and the hands and feet can overlap each other. The external genitalia is prominent but not yet sexually distinct. Many nuclei, fiber tracts, decussations and commissures are evident in the brainstem. All named muscles can be identified.


New structures include caudate nucleus, coronary arteries, flocculus of cerebellum, fundus of bladder, neopallial cortex, piriform cortex (paleopallium), radial artery.

Section 104

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