Describe the process of cleavage upto the formation of blastocyst

Explanation

### Step-by-Step Solution:

1. **Definition of Cleavage**: Cleavage is the series of rapid cell divisions that occur after fertilization, leading to the formation of a multicellular embryo. In humans, this process is termed **holoblastic cleavage**, meaning that the entire zygote divides completely.

2. **First Cleavage Division**: The first cleavage occurs along the **meridional axis** of the zygote, resulting in the formation of two cells. This division takes place approximately **15 hours after fertilization**.

3. **Second Cleavage Division**: The second cleavage is characterized by a **rotational cleavage pattern**. One of the two cells divides along the **equatorial plane**, while the other continues to divide along the **meridional plane**. This results in the formation of a **four-cell stage**.

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