During the reproductive cycle of a human female, when, where and how does a Placenta develop ? What is the function of placenta during pregnancy and embryo development?

Explanation

### Step-by-Step Solution:

1. **Formation of Zygote**:
- The reproductive cycle begins with the fusion of a sperm and an ovum, resulting in the formation of a zygote.

2. **Development of Blastocyst**:
- The zygote undergoes mitotic divisions (cell cleavage) to form a structure called the blastocyst.

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