What cells, occasionally seen in bone marrow biopsy specimens, are responsible for the formation of bone?

Osteoblasts are specialized cells that play a critical role in bone formation. They are responsible for synthesizing and secreting the bone matrix, which consists of collagen and other proteins that provide the framework for bone tissue. Additionally, osteoblasts facilitate the mineralization of this matrix, contributing to the hardening and strength of bones.

Their presence in bone marrow biopsy specimens indicates ongoing bone remodeling and development, as osteoblasts are actively involved in the process of building new bone tissue. This activity is essential during growth and healing after fractures, as well as in maintaining bone density and overall skeletal health.

In contrast, the other cells mentioned serve different functions related to the immune response or bone resorption, rather than the formation of bone. For instance, macrophages are involved in phagocytosis and immune responses, plasma cells produce antibodies, and osteoclasts are responsible for breaking down bone tissue. Therefore, osteoblasts are specifically linked to bone formation, making them the correct choice in this context.