What are the types of bone cells?

There are four types of bone cells. 

1. Osteogenic or osteoprogenitor cells: Found in the deep layers of the periosteum and the marrow, osteogenic cells originate from pluripotent mesenchymal stem cells (MSCs) of the bone marrow. They develop into osteoblasts. 
2. Osteoblasts: Derived from osteoprogenitor cells, osteoblasts are cuboidal, mono-nucleate bone-forming cells. They constitute 4-6% of all bone cells and are responsible for synthesizing bone matrix, collagen, and other organic compounds, all of which contribute significantly to bone formation and maintaining the structural shape of bone. Osteoblasts also play a role in depositing minerals into the bone matrix, which contributes to bone hardness. After forming the bone matrix, some osteoblasts develop into bone lining cells that cover bone surfaces while others get trapped in the bone and transform into osteocytes. The remaining osteoblasts undergo apoptosis or programmed cell death. 
3. Osteocytes: Osteocytes are mature bone cells that are derived from osteoblasts that are surrounded and trapped by their own secretions during bone formation. These are the most abundant type of bone cells in mature adult bone tissue, making up 90-95% of all bone cells. They are star-shaped with characteristic dendritic processes and lack mitotic activity. Osteocytes serve multiple functions. They regulate osteoblastic and osteoclasic activities, and contribute to maintenance of bone tissue and mineral concentration of the matrix. Osteocytes are also crucial for communication within bone tissue.  They communicate with one another through long channels in the bone matrix called canaliculi, which they also use to transfer nutrients and waste products. 
4. Osteoclasts: Osteoclasts are large, multinucleated bone-resorbing cells that originate from white blood cells of the hematopoietic stem cell lineage. They are typically found on the surface of bone tissue. Osteoclasts are primarily involved in bone resorption and bone remodeling. They secrete enzymes that dissolve the organic components and matrix of the bone, break down damaged or old bone tissue and release essential minerals such as phosphate and calcium into the bloodstream, which supports the body’s metabolic needs.