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[1] Light micrograph of a nidus consisting of osteoprogenitor cells that are displaying a prominent Golgi apparatus. The process of intramembranous ossification starts when a small group of adjacent MSCs begin to replicate and form a small, dense cluster of cells that is called a nidus. [a] Once a nidus has been formed the MSCs within it stop ...
It is synonymous with bone tissue formation. [1] There are two processes resulting in the formation of normal, healthy bone tissue: [2] Intramembranous ossification is the direct laying down of bone into the primitive connective tissue , while endochondral ossification involves cartilage as a precursor.
A dermal bone or investing bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrate skeleton, including much of the skull, jaws, gill covers, shoulder girdle, fin rays (lepidotrichia), and the shells of turtles and armadillos.
[1] The bones that form the base and facial regions of the skull develop through the process of endochondral ossification. In this process, mesenchyme accumulates and differentiates into hyaline cartilage, which forms a model of the future bone. The hyaline cartilage model is then gradually, over a period of many years, displaced by bone.
The periosteum is a membrane that covers the outer surface of all bones, [1] except at the articular surfaces (i.e. the parts within a joint space) of long bones. (At the joints of long bones the bone's outer surface is lined with "articular cartilage", a type of hyaline cartilage.)
The skull is a complex structure; its bones are formed both by intramembranous and endochondral ossification. The skull roof bones, comprising the bones of the facial skeleton and the sides and roof of the neurocranium, are dermal bones formed by intramembranous ossification, though the temporal bones are formed by endochondral ossification.
It usually consists of only endochondral ossification. Sometimes, intramembranous ossification occurs together with endochondral ossification. Intramembranous ossification, mediated by the periosteal layer of bone, occurs with the formation of callus. For endochondral ossification, deposition of bone only occurs after the mineralised cartilage.
The parietal eminence (parietal boss, parietal tuber, parietal tuberosity) is a convex, smooth eminence on the external surface of the parietal bone of the skull.It is the site where intramembranous ossification of the parietal bone begins during embryological development.