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The first step in the process is the formation of bone spicules which eventually fuse with each other and become trabeculae. The periosteum is formed and bone growth continues at the surface of trabeculae. Much like spicules, the increasing growth of trabeculae result in interconnection and this network is called woven bone.
This newly formed bone can be called "periosteal bone" as it originates from the transformed periosteum. However, considering its developmental pathway, it could be classified as "intramembranous bone". [8] After the formation of the periosteum, chondrocytes in the primary center of ossification begin to grow (hypertrophy).
The formation of bone is called ossification. During the fetal stage of development this occurs by two processes: intramembranous ossification and endochondral ossification. [42] Intramembranous ossification involves the formation of bone from connective tissue whereas endochondral ossification involves the formation of bone from cartilage.
This decreases bone formation, and is not a problem when a person has healthy bones. [126] It is thought, though, that decreasing the concentration of sclerostin in the body may lead to the formation of more bone, and that is the premise as to why monoclonal antibodies that reduce the concentrations of naturally occurring sclerostin may help ...
The three main mechanisms by which osteoporosis develops are an inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive bone resorption, and inadequate formation of new bone during remodeling, likely due to mesenchymal stem cells biasing away from the osteoblast and toward the marrow adipocyte ...
A 2018 Swedish systematic review found that GnRH modulators had similar pain-relieving effects to gestagen, but also decreased bone density. [114] Aromatase inhibitors are medications that block the formation of estrogen and have become of interest for researchers who are treating endometriosis. [152]
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
They may have lived as early as 4.28 Gya (billion years ago), relatively soon after the formation of the oceans 4.41 Gya, not long after the formation of the Earth 4.54 Gya. [ 78 ] Early micro-fossils may have come from a hot world of gases such as methane, ammonia, carbon dioxide, and hydrogen sulfide , toxic to much current life. [ 216 ]