How many radial spokes are present in internal structure of cilia?

Answer

To determine the number of radial spokes present in the internal structure of cilia, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Cilia**: Cilia are composed of a central core known as the axoneme, which is made up of microtubules.

2. **Identify the Arrangement of Microtubules**: The axoneme has a characteristic arrangement known as the "9 + 2" structure. This means there are 9 peripheral microtubule doublets surrounding 2 central microtubules.

3. **Focus on the Peripheral Microtubules**: The 9 peripheral microtubules are arranged in pairs, called doublets.

4. **Determine the Role of Radial Spokes**: Radial spokes connect the peripheral doublets to the central pair of microtubules.

5. **Count the Radial Spokes**: Each of the 9 peripheral doublets is connected to the central pair by a radial spoke. Therefore, there are 9 radial spokes in total.

### Final Answer:
There are **9 radial spokes** present in the internal structure of cilia.

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