In human female the blastocyst :-

Options

A. Gets implanted into uterus 3 days after ovulation
B. Gets nutrition from uterine endometrial secretion only after implantation
C. Gets implanted in endometrium by the trophoblast cells
D. Forms placenta even before implanation

Answer

To answer the question "In human female, the blastocyst:", we will analyze the characteristics and processes associated with the blastocyst in relation to implantation and its development.

### Step-by-Step Solution:

1. **Understanding the Blastocyst Formation**:
- The blastocyst is formed approximately 5 days after fertilization. It consists of an outer layer of cells called the trophoblast and an inner cell mass that will eventually develop into the embryo.

2. **Timing of Implantation**:
- The blastocyst gets implanted into the uterus about 5 days after fertilization, not 3 days after ovulation. This is a crucial detail as it establishes the timeline for implantation.

3. **Nutritional Source**:
- Initially, the blastocyst does not receive nutrition from the uterine endometrial secretions until after implantation. Once the trophoblast cells attach to the endometrium, they begin to form the placenta, which will then provide nutrition.

4. **Role of Trophoblast Cells**:
- The trophoblast cells play a vital role in the implantation process. They attach the blastocyst to the endometrium (the inner lining of the uterus) and are responsible for the formation of the placenta.

5. **Formation of the Placenta**:
- The placenta is formed after the implantation process begins, not before. The trophoblast cells differentiate and contribute to the formation of the placenta once the blastocyst is securely implanted.

6. **Conclusion**:
- The correct statement regarding the blastocyst in human females is that it gets implanted in the endometrium by trophoblast cells. Therefore, the correct option is that the blastocyst gets implanted in the endometrium by trophoblast cells.

### Final Answer:
The correct statement is: **The blastocyst gets implanted in the endometrium by trophoblast cells.**