The third ventricle of brain is connected to the fourth ventricle of brain through __________.

Options

A. Foramen of Monro
B. Duct of Sylvius
C. Metacoel
D. Eustachian tube

Answer

To solve the question regarding the connection between the third and fourth ventricles of the brain, we need to analyze the options provided.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks how the third ventricle of the brain connects to the fourth ventricle. We need to identify the correct anatomical structure that serves as this connection.

2. **Reviewing the Options**:
- **Option 1: Foramen of Monroe**: This foramen connects the lateral ventricles to the third ventricle, not the third to the fourth. Therefore, this option is incorrect.
- **Option 2: Duct of Sylvius (Aqueduct of Sylvius)**: This duct is known to connect the third ventricle to the fourth ventricle. This option is likely correct.
- **Option 3: Mataseel**: This term does not correspond to any known anatomical structure connecting the third and fourth ventricles. Thus, this option is incorrect.
- **Option 4: Eustachian Tube**: The Eustachian tube connects the middle ear to the nasopharynx and is unrelated to the brain's ventricular system. Hence, this option is also incorrect.

3. **Conclusion**: After evaluating all options, the only correct answer is **Option 2: Duct of Sylvius (Aqueduct of Sylvius)**, which connects the third ventricle to the fourth ventricle of the brain.

### Final Answer:
The third ventricle of the brain is connected to the fourth ventricle of the brain through **the Duct of Sylvius (Aqueduct of Sylvius)**.

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