One of the following is not a part of membranous labyrinth

Options

A. Semicircular canal
B. Cochlear duct
C. Vestibule
D. Bony labyrinth

Answer

To answer the question "One of the following is not a part of the membranous labyrinth," we need to identify which option does not belong to the membranous labyrinth structure.

### Step-by-Step Solution:

1. **Understand the Structure of the Inner Ear**: The inner ear consists of two main components: the bony labyrinth and the membranous labyrinth. The bony labyrinth is a rigid, bony outer structure, while the membranous labyrinth is a system of soft, flexible ducts filled with fluid.

2. **Identify the Components of the Membranous Labyrinth**:
- The membranous labyrinth includes:
- **Cochlear Duct**: This is part of the cochlea and is responsible for hearing.
- **Semicircular Ducts**: There are three of these, which are involved in balance.
- **Saccule and Utricle**: These are part of the vestibule and help with balance and spatial orientation.

3. **Analyze the Options Given**:
- **Semicircular Canal**: This is part of the bony labyrinth, but it contains the semicircular ducts which are part of the membranous labyrinth.
- **Cochlear Duct**: This is a part of the membranous labyrinth.
- **Vestibule**: This contains the saccule and utricle, which are part of the membranous labyrinth.
- **Bony Labyrinth**: This is the rigid outer structure and is not part of the membranous labyrinth.

4. **Conclusion**: The option that is not a part of the membranous labyrinth is the **Bony Labyrinth**.

### Final Answer:
The correct answer is **Bony Labyrinth**.