What kind of filaments are cillia and flagella composed of?

Options

A. microtubules
B. microfilaments
C. microfibrils
D. microvilli

Answer

### Step-by-Step Solution:

1. **Understanding Cilia and Flagella**:
- Cilia and flagella are specialized structures that facilitate movement in cells. They can either move the cell itself or help in moving fluids around the cell.

2. **Composition of Cilia and Flagella**:
- The primary components of cilia and flagella are microtubules. These are cylindrical structures that play a crucial role in maintaining the shape of the cell and facilitating movement.

3. **Structure of Cilia and Flagella**:
- The arrangement of microtubules in cilia and flagella is characterized by a "9 + 2" structure. This means there are nine pairs of peripheral microtubules (doublets) arranged in a circle, with two central microtubules.

4. **Details of the Arrangement**:
- In the "9 + 2" arrangement, the nine peripheral doublets are connected by proteins called dyneins, which facilitate movement. The two central microtubules are surrounded by a sheath.

5. **Conclusion**:
- Therefore, the correct answer to the question is that cilia and flagella are composed of microtubules.