The Stages of Human Embryonic Development

Stage 15 embryos are characterized by the closure of the lens vesicles, the appearance of the nasal pits and the formation of distinct hand plates. The form of the upper limb buds is the most constant characteristic of stage 15.

Most embryos of this stage have a greatest length of between 7 and 8 mm but they can range from 6 to 11 mm. They have an estimated postfertilization age of between 33 and 38 days.