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the bon 1

الكلية كلية طب الاسنان     القسم  العلوم الاساسية     المرحلة 2
أستاذ المادة ندى مهدي عبد الرضا الخفاجي       16/01/2020 04:58:30
The Bone
Specialized connective tissue composed of intercellular calcified material( bone matrix)and types of cell (osteocyte , osteoblast, osteoclast) .the bone covered and lined by periosteum & endosteum.
Function
Support for the body, protection of many organs such as crainl thorasic cavities , harbors cavities for bone marrow(where blood cells are formed) , homeostatic regulation of blood calcium , phosphate and other ions , and muscle attachment.
1-Bone matrix
Which consist inorganic matter represent about 60%of the dry weight of bone matrix(calcium ,phosphorous and hydroxyapatite)are especially abundant, but bicarbonate, citrate, magnesium, potassium and sodium)are also found. The organic matter( type I collagen proteoglycans , glycoproteins , growth factor & cytokines) and water. There are space within the matrix called Lacunae (housed the osteocyte) which are connected by little tunnels called canaliculi and this allow contact between osteocytes )which extend processes into canaliculi) and blood vesseles.









Bone cells
Osteoprogenitor cells: Mesenchyme stem cells that divide to produce osteoblasts . Are located in inner, cellular layer of periosteum . Assist in fracture repair .

Osteoblasts: Immature bone cells that secrete matrix compounds (osteogenesis).It lined up side by side resemble to simple epithelial tissue and have cuboidal or polygonal shape and basophilic cytoplasm when it active but it seem to be flatten if activity decline. Osteoblasts may change to osteocytes.









Osteocytes: Flat and almond shaped cell found in cavities (lacunae) between bone matrix layers (which formed during the manufacture of the new matrix osteoid), extend cytoplasmic processes through canaliculi for exchanges between osteocytes and blood capillaries (Because metabolites are unable to diffuse through the calcified matrix of bone).

Osteoclasts: Large multinucleated, branched, motile cells lie within (howship,s lacunae) and belong to the mononuclear phagocyte system. The surface of cells –facing matrix have projections –ruffled border (related to the activity) and release lysosomes into the extracellular space to phagocytic and remodeling. The activity of this cell is controlled by a cytokine called osteoclast-stimulating factor* and hormones .the osteoclast have receptor for calcitonin and thyroid hormone but not for parathyroid .


Bone Membranes


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .