Howships lacunae contain:
**Core Concept**
Howship's lacunae are small depressions or cavities found on the surface of the bone, particularly in the area of the periosteum. They play a crucial role in the process of bone resorption, allowing osteoclasts to penetrate the bone matrix and initiate the breakdown of bone tissue.
**Why the Correct Answer is Right**
The correct answer is related to the process of bone resorption, which involves the action of osteoclasts. Howship's lacunae serve as a conduit for these cells to access the bone matrix and initiate the breakdown of bone tissue. This process is essential for bone remodeling and is mediated by various enzymes and signaling pathways, including the RANKL-RANK-OPG pathway.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Howship's lacunae are not involved in bone formation, but rather in bone resorption.
**Option B:** This option is incorrect because osteoblasts are responsible for bone formation, not bone resorption, and are not associated with Howship's lacunae.
**Option C:** This option is incorrect because the Haversian canals are involved in the transport of blood vessels and nerves within the bone, not in bone resorption.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that bone resorption is a critical process in bone remodeling, and Howship's lacunae play a key role in this process. Understanding the mechanisms of bone resorption is crucial for managing conditions such as osteoporosis and Paget's disease.
**Correct Answer: D. Osteoclasts.**