During which phase of human development does implantation of the embryo into the uterine wall normally occur?

• A. Immediately after fertilization
• B. At the end of the first trimester
• C. About 6-7 days after fertilization
• D. During ovulation

Answer: (C)

Verified step by step guidance

1. Understand the process of fertilization: Fertilization occurs when a sperm cell successfully merges with an egg cell, forming a zygote. This marks the beginning of human development.
2. Learn about the zygote's journey: After fertilization, the zygote undergoes several rounds of cell division (cleavage) as it travels down the fallopian tube toward the uterus. This process typically takes a few days.
3. Recognize the formation of the blastocyst: By the time the zygote reaches the uterus, it has developed into a structure called a blastocyst, which consists of an outer layer (trophoblast) and an inner cell mass that will eventually form the embryo.
4. Understand implantation timing: Implantation occurs when the blastocyst attaches to the uterine wall. This process typically happens about 6-7 days after fertilization, not immediately after fertilization, during ovulation, or at the end of the first trimester.
5. Clarify the importance of implantation: Implantation is a critical step in pregnancy, as it allows the embryo to establish a connection with the mother's blood supply for nutrients and waste exchange, enabling further development.