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How does an embryo change during the seventh and eighth weeks after conception?
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During the seventh and eighth weeks of development, the embryo undergoes significant changes as it transitions from a state distinguishing it as a primate to one that is recognizably human. This period is part of organogenesis, a critical phase lasting from the third to the eighth week where organ development occurs.123
Key developments during this time include:
- Human Characteristics: Developmental changes advance to create a recognizably human form.1
- Genital Development: The genital organs begin to develop, though the embryo remains in an indifferent stage where the sex is not yet grossly distinguishable.4
- Growth and Transition: By the end of the second month, the embryo reaches a length of approximately 30 mm (1.2 inches). At this point, the embryonic stage concludes, and the developing conceptus is referred to as a fetus until birth.12
Because this is a period of rapid organ formation, it is also a time when certain congenital defects, such as cleft palate, may occur.3