In which stage does the embryo differentiate into trophoblast and an inner group of cells ?

Options

A. Gastrula
B. Neural
C. Blastula
D. Morula

Answer

To solve the question regarding the stage in which the embryo differentiates into trophoblast and an inner group of cells, we can analyze the options provided:

1. **Understanding the stages of embryonic development**:
- The embryonic development progresses through several stages: zygote, cleavage, blastula, gastrula, and neurula.
- Each stage has distinct characteristics and functions.

2. **Analyzing the options**:
- **Option 1: Gastrula**: The gastrula stage is characterized by the formation of three germ layers (ectoderm, mesoderm, and endoderm) and does not involve differentiation into trophoblast and inner cell mass.
- **Option 2: Neural**: The neurula stage follows gastrulation and involves the formation of the neural tube. This stage also does not involve the differentiation into trophoblast and inner cell mass.
- **Option 3: Blastula**: The blastula stage is characterized by a hollow ball of cells. It is during this stage that the embryo differentiates into the trophoblast (the outer layer) and the inner cell mass (which will eventually form the embryo).
- **Option 4: Not applicable**: Since the previous options have been analyzed, we can conclude that this option is irrelevant.

3. **Conclusion**:
- The correct answer is **Option 3: Blastula**, as this is the stage where the embryo differentiates into trophoblast and an inner group of cells.

### Step-by-Step Solution:
1. Understand the stages of embryonic development.
2. Analyze each option provided:
- Gastrula: Incorrect, as it involves germ layer formation.
- Neural: Incorrect, as it follows gastrulation and involves neural development.
- Blastula: Correct, as it is the stage where trophoblast and inner cell mass form.
3. Conclude that the correct answer is Blastula.