The dramatic muscle growth that occurs after birth occurs by 

Options

A. Hypertrophy
B. Hyperplasia
C. Neoplasia
D. Castration

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the type of muscle growth that occurs dramatically after birth.

2. **Identifying Incorrect Options**:
- **Castration**: This refers to the removal of the testicles and is not related to muscle growth. Therefore, it can be eliminated as an option.
- **Neoplasia**: This term refers to abnormal and uncontrolled growth of cells or tissues, which can lead to diseases like cancer. Since the question pertains to normal muscle growth, this option is also incorrect.

3. **Analyzing the Remaining Options**:
- **Hyperplasia**: This term means an increase in the number of cells in a tissue or organ. While this can contribute to growth, it is not the primary mechanism for muscle growth after birth.
- **Hypertrophy**: This term refers to the increase in the size of existing muscle cells. During postnatal growth, muscle growth predominantly occurs through hypertrophy, meaning the existing muscle cells grow larger rather than new cells being formed.

4. **Conclusion**: Given that muscle growth after birth primarily occurs through the enlargement of existing muscle cells, the correct answer is **hypertrophy**.

**Final Answer**: The dramatic muscle growth that occurs after birth occurs by **hypertrophy**.

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