Implantation occurs at ?
**Core Concept**
Implantation refers to the process by which a fertilized egg, or blastocyst, attaches to the wall of the uterus. This process is crucial for the establishment of a successful pregnancy. **Implantation** occurs approximately 6-10 days after fertilization.
**Why the Correct Answer is Right**
The correct answer is related to the timing and location of implantation in the female reproductive cycle. Implantation is facilitated by the **trophoblast** cells of the blastocyst, which invade the **endometrium**, the lining of the uterus. This process is supported by the production of **human chorionic gonadotropin (hCG)** and other hormones.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the timing of implantation.
**Option B:** Similarly, this option is incorrect as it suggests a different timing.
**Option D:** This option is also incorrect as it does not correspond with the known timing of implantation.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that implantation typically occurs about 6-10 days after fertilization, which is crucial for understanding early pregnancy and potential complications.
**Correct Answer:** D. 6-10 days after fertilization.