By the end of which gestational week are all organ systems in the fetus typically present?

By the end of eight weeks of gestation, all organ systems in the fetus are typically present. This period marks the end of the embryonic stage and the beginning of the fetal stage of development. During these first eight weeks, significant organogenesis occurs, where the foundations for all major organ systems are formed, including the cardiovascular, respiratory, and digestive systems, as well as the beginnings of limbs and facial features.

The importance of this milestone cannot be overstated, as the embryo transitions into a fetus, and this is when the fetus begins to take on human characteristics. After eight weeks, fetal development continues with the maturation and growth of these systems, but the basic structures are already established.

Options indicating earlier gestational weeks suggest that not all organ systems would be fully formed, as organogenesis is a complex process that primarily occurs during this eight-week window. After eight weeks, while development is ongoing, and systems are refining and maturing, the essential presence of organs is already accomplished.