Which of the following is true concerning osteoclasts?

Options

A. They develop from white blood cells
B. They are produced from osteoprogenitor cells
C. They are located in lacunae
D. They are responsible for the exchange of nutrients and wastes with the blood

Explanation

### Step-by-Step Solution:

1. **Understanding Osteoclasts**:
- Osteoclasts are specialized cells involved in the resorption of bone. They play a critical role in bone remodeling by breaking down bone tissue.

2. **Analyzing the Options**:
- **Option A**: "They develop from white blood cells."
- Osteoclasts are indeed related to the immune system, but they do not directly develop from white blood cells. Instead, they originate from the fusion of monocytes/macrophages in the bone marrow.
- **Conclusion**: This option is incorrect.

- **Option B**: "They are produced from osteoprogenitor cells."
- Osteoclasts do not arise from osteoprogenitor cells; these cells primarily give rise to osteoblasts, which are responsible for bone formation.
- **Conclusion**: This option is incorrect.

- **Option C**: "They are located in the lacunae."
- Osteoclasts are indeed found in small pits on the bone surface known as lacunae or resorption bays, where they carry out their function of bone resorption.
- **Conclusion**: This option is correct.

- **Option D**: "They are responsible for the exchange of nutrients and waste with the blood."
- This function is not performed by osteoclasts. Instead, osteoclasts are primarily involved in the breakdown of bone tissue, not in nutrient exchange.
- **Conclusion**: This option is incorrect.

3. **Final Answer**:
- The correct statement concerning osteoclasts is: **They are located in lacunae**.