round swelling at the dorsal portion of the midbrain is known as

Answer

**Step-by-Step Solution:**

1. **Identify the Location of the Midbrain:**
- The midbrain is situated between the forebrain (specifically the thalamus) and the hindbrain (specifically the pons).

2. **Understand the Structure of the Midbrain:**
- The midbrain has a dorsal surface that features specific structures.

3. **Recognize the Key Features of the Dorsal Surface:**
- The dorsal surface of the midbrain consists of two pairs of rounded lobes.

4. **Name the Rounded Lobes:**
- These rounded lobes are known as the "corpora quadrigemina."

5. **Conclude the Answer:**
- Therefore, the round swelling at the dorsal portion of the midbrain is called the "corpora quadrigemina."

**Final Answer:**
The round swelling at the dorsal portion of the midbrain is known as the **corpora quadrigemina**.

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