What is the term for unborn offspring in the stage of development from implantation to the end of the eighth week of pregnancy?

The term for unborn offspring from the time of implantation through to the end of the eighth week of pregnancy is "embryo." During this stage of development, the fertilized egg, which has already undergone several divisions, settles into the womb and begins to embed itself into the uterine lining. The embryo undergoes crucial developmental processes, including the formation of major organs and body structures.

The embryonic period is significant because it is during these weeks that the foundations for all major body systems are established. This is a time of rapid cell division and differentiation, where the developing organism is particularly sensitive to environmental influences, which can affect the development positively or negatively.

In contrast, the term "fetus" refers to the later stage of development that begins after the eighth week, once the foundational structures have developed. "Blastocyst" refers to a specific early stage of embryonic development, occurring right after fertilization, when the embryo is still in a solid ball of cells before several layers are formed and implantation occurs. A "zygote" is the very first stage formed immediately after the sperm and egg unite, representing a single cell before any cell division or further development takes place.