The connection between osteoblasts and osteocytes is that an osteocyte is the mature version of an osteoblast. Both osteoblasts and osteocytes are essential to the proper maintenance of bone structure. In a living being, bone is a matrix of bone cells, incorporating blood vessels, nerves, and other structures. To maintain the bone matrix, several different cells are at work. Two of them are osteoclasts, cells which constantly break down bone, and osteoblasts, flat or cuboid shaped cells which constantly build up bone.
At first glance, it may seem as if osteoclasts are the "bad guys" of bone health. Osteoclasts do break down bone, but they also help to maintain the body's proper calcium levels, and they make way for osteoblasts. After the osteoclasts have excavated an area, osteoblasts come in and rebuild it, allowing new bone to take the place of old bone. If it wasn't for this constant tearing down and building up, bone would become brittle and could break easily.
Osteoblasts build bone by secreting layer after layer of a bone foundation, called osteoid, which is then filled in with inorganic salts to become bone. In doing this, there may come a time when the osteoblast becomes encased in the very bone it helps to make. This is when the connection between osteoblasts and osteocytes can be seen. Osteocytes are osteoblasts that have been encased within bone. These osteocytes have tentacle like structures that allow them to maintain communication with one another as they are being encased.
Both osteoblasts and osteocytes are living cells, and, as such, need nutrition. Once encased in bone, the only openings an osteocyte has to nutrition are channels that are created around the osteocytes' extensions. These channels, or canaliculi, not only allow the osteocyte to maintain communication with each other, but also allow it access to nutrients and to get rid of wastes. Once the cell is enclosed, the osteocyte looses much of its ability to form bone. It does not, however, lose all of its usefulness.
Osteoblasts and osteocytes both have unique jobs in keeping up bone health. For the osteocyte encased in the bone structure, that job is to maintain the bone from the inside. In addition, osteocytes can indicate to other cells that something is wrong with the bone tissue. For example, it can signal when a bone is injured or if there is something in the environment that can cause damage to the bone. Once signaled, other cells can rush in and repair the damage or correct the problem, if possible.