During the first stage of pregnancy, what significant development occurs about two weeks after fertilization?

During the first stage of pregnancy, what significant development occurs about two weeks after fertilization?

• A. The egg is expelled from the body
• B. The blastocyst becomes an embryo
• C. The fetus becomes recognizable as human
• D. The placenta forms

Answer: (B)

About two weeks after fertilization, the significant development that occurs is the transition of the blastocyst into an embryo. After fertilization, the zygote begins to divide and develop into a blastocyst as it moves down the fallopian tube towards the uterus. Once it reaches the uterus, typically around five to six days post-fertilization, the blastocyst implants into the uterine lining. By approximately two weeks after fertilization, this blastocyst begins to undergo further differentiation and development, marking the point at which it is referred to as an embryo. This embryonic stage is crucial as it sets the foundation for the formation of the structures and systems that will support the developing fetus throughout pregnancy. The recognition of the embryo is typically marked by the beginning of the organization of cell layers, which will eventually develop into organs and tissues. In contrast, the expelling of the egg from the body happens during menstruation rather than during early pregnancy. The fetus only becomes recognizable as a human later in the pregnancy, usually around the end of the first trimester, when distinct features can be identified. The placenta does begin to form shortly after the implantation of the blastocyst, but its full development and functionality are more pronounced at a later

About two weeks after fertilization, the significant development that occurs is the transition of the blastocyst into an embryo. After fertilization, the zygote begins to divide and develop into a blastocyst as it moves down the fallopian tube towards the uterus. Once it reaches the uterus, typically around five to six days post-fertilization, the blastocyst implants into the uterine lining. By approximately two weeks after fertilization, this blastocyst begins to undergo further differentiation and development, marking the point at which it is referred to as an embryo.

This embryonic stage is crucial as it sets the foundation for the formation of the structures and systems that will support the developing fetus throughout pregnancy. The recognition of the embryo is typically marked by the beginning of the organization of cell layers, which will eventually develop into organs and tissues.

In contrast, the expelling of the egg from the body happens during menstruation rather than during early pregnancy. The fetus only becomes recognizable as a human later in the pregnancy, usually around the end of the first trimester, when distinct features can be identified. The placenta does begin to form shortly after the implantation of the blastocyst, but its full development and functionality are more pronounced at a later