Bismillah, [Osteitis fibrosa cystica] # Mechanism: Hypocalcemia (for instance)-->Hyperparathyroidism--> Osteoclastic bone resorption releases minerals, including calcium, from the bone into the bloodstream-->In addition to elevated blood calcium levels, over-activity of this process results in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue (peritrabecular fibrosis), and the formation of cyst-like brown tumors in and around the bone-->produce symptoms of the disease due to the general softening of the bones and the excess calcium in the blood--> include bone fractures, kidney stones, nausea, moth-eaten appearance in the bones, appetite loss, and weight loss. ** The brown tumor: --> is a bone lesion that arises in settings of excess osteoclast activity, such as hyperparathyroidism. It is not a true neoplasm, as the term tumor suggests; however, it may mimic a true neoplasm.. Brown tumours are radiolucent on x-ray Brown tumours consist of: - fibrous tissue, woven bone and supporting vasculature, but no matrix. The osteoclasts consume the trabecular bone that osteoblasts lay down -->and this front of reparative bone deposition followed by additional resorption can expand beyond the usual shape of the bone, involving the periosteum --> causing bone pain. -->The characteristic brown coloration results from hemosiderin deposition into the osteolytic cysts. *Hemosiderin deposition is not a distinctive feature of brown tumors; it may also be seen giant cell tumors of the bone ** A trabecula: -->(plural trabeculae, from Latin for small beam) is a small, often microscopic, tissue element in the form of a small beam, strut or rod, --> F(x) = having a mechanical function, --> composed of dense collagenous tissue (such as the trabecula of the spleen.) They can be composed of other materials; in the heart, for example, muscles such as trabeculae carneae and septomarginal trabecula form similar structures. The formation of trabeculae is known as trabeculation. On histological section, trabeculae of a cancellous bone can look like a septum, but in three dimensions they are topologically distinct, with trabeculae being roughly rod or pillar-shaped and septa being sheet-like. --> F(x) = a) When crossing fluid-filled spaces, trabecula may have the function of resisting tension (as in the penis, see for example trabeculae of corpora cavernosa and trabeculae of corpus spongiosum) b) or providing a cell filter (as in the trabecular meshwork of the eye.) --> Multiple perforations in a septum may reduce it to a collection of trabecula, as happens to the walls of some of the pulmonary alveoli in emphysema. -->In OFC, resorption of Ca2+ from trabeculae (N: has collegenous fibre + Ca2+ ) will result in fibrosis (trabeculae with collegenous fibre but without Ca2+) --> the bone will have fibrosed tissue instead of bone (my theory**).
Posted on: Fri, 26 Dec 2014 21:56:49 +0000
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