Which of the following is correct about the blastocyst ?

Options

A. Penetrates endometrium from its embryonic pole.
B. Consists of outer trophoblast and inner embryoblast.
C. Gets implanted along with zona pellucida.
D. Has a cavity called amniotic cavity

Answer

To answer the question "Which of the following is correct about the blastocyst?", we will analyze the characteristics of the blastocyst based on the information provided.

### Step-by-Step Solution:

1. **Understanding the Formation of the Blastocyst**:
- After fertilization, the zygote undergoes several rounds of cell division (cleavage) and eventually forms a solid ball of cells known as the morula.
- The morula then develops into a blastula, which is characterized by the formation of a fluid-filled cavity called the blastocoel.

2. **Structure of the Blastocyst**:
- The blastocyst consists of two main components:
- **Trophoblast**: The outer layer of cells that will eventually contribute to the formation of the placenta.
- **Inner Cell Mass (Embryoblast)**: The inner mass of cells that will develop into the embryo.

3. **Implantation Process**:
- The blastocyst attaches to the uterine lining (endometrium) for implantation.
- It is important to note that the blastocyst penetrates the endometrium from the **ab-embryonic pole**, not the embryonic pole.

4. **Zona Pellucida**:
- The zona pellucida is a protective glycoprotein layer surrounding the blastocyst.
- This layer is shed during the implantation process, meaning the blastocyst does not implant along with the zona pellucida.

5. **Amniotic Cavity**:
- The amniotic cavity is not present in the blastocyst. It is formed later during the development of the embryo after implantation, primarily from the ectoderm.

### Conclusion:
Based on the analysis, the correct statement about the blastocyst is:
- **Blastocyst consists of outer trophoblast and inner embryoblast.** (This corresponds to option 2.)