Learning Bone Growth 2: The Osteoblast and Woven Bone Formation

Learning Bone Growth 2 – The Osteoblast (OB) and Woven Bone Formation, provides a detailed outline of the OB, it origin from the mesenchymal stem cell, its pluripotential nature, and the function of this complex cell which is the only agent producing bone in the human. The lifespan and efficiency of the OB are compared to that of the osteoclast (OCl), the only cell deleting bone and mineralized matrix in the human. Note the important fact that the OCl is highly efficient, and the OB is not. The OCl deletes 3 times its cell volume in its very short 1-2 day lifespan. The OB lives 10 days while actively making bone, and collectively, it takes a full 3 months and a team of 100 – 150 OBs to replace the bone removed by one osteoclast. THIS DISCREPANCY IS THE KEY FACTOR LEADING TO STRESS REACTIONS AND FRACTURES, A KEY CLINICAL CONCEPT.
The hematoxylin and eosin-stained (H & E) microscopic slides provide static images of the process of bone formation. Of ten OBs actively making bone, nine will die an apoptotic death, provide “food” for the process to continue. One of ten is selected by an unknown process to become a resident, mature osteocyte, buried in bone. There are 46 million osteocytes in the human body, responsible for an astonishing 23 million cell-to-cell connections, similar in complexity to the human brain. The multiplex nature of bone boggles the mind. To return to the slides, what is missing in the static images on one slide, is motion. It takes imagination to realize all that is occurring, as bone is being elaborated by the OB. The cells are motile, moving to the site of osteoid deposition, attaching to the osteoid that is there. At a subcellular level, osteogenic markers cause the cell to change function. The markers, convoluted chemicals undergo internal shifts in chemical conformity allowing the required activity, the elaboration of bone matrix, to occur. At every step complicated change in each cell, and in the structure itself occurs. Failure at any step can be clinically relevant, leading to OSTEOPOROSIS (OP), a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. THE VIDEO DESCRIBES THS CLINICALLY IMPORTANT DIFFERENTIAL DIAGNOSIS OF Osteoporosis, WHEREIN YOU CAN HAVE:  TOO LITTLE FORMATION OF BONE, A DEFECT OF OB FUNCTION; TOO MUCH DELETION OF BONE, A DEFECT OF OCL FUNCTION; OR A LOSS OF BALANCE OF BOTH.