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VIRTUAL MICROSCOPY histopath.westernu.edu BONE Slides: BN 1-7 1. Intramembranous bone formation (BN 1-3). This is a portion of a mandible undergoing intramembranous ossification. Observe the trabeculae of bone (lying in a bed of mesenchymal C.T) and the entrapped OSTEOCYTES WITHIN OSTEOID. Identify the basophilic OSTEOBLASTS lining the surface of the trabeculae and multinucleate OSTEOCLASTS where present. 2. Endochondral bone formation (BN 4 & 10). This example of a developing long bone will illustrate ENDOCHONDRAL ossification. In the epiphyseal plate region, clones of CHONDROBLASTS are formed (ZONE OF PROLIFERATION). Proceeding toward the diaphysis, the chondrocytes become aligned into columns and hypertrophy (ZONE OF MATURATION). As the marrow cavity is approached, the matrix between the chondrocytes calcifies (ZONE OF CALCIFICATION). Blood vessels from the marrow cavity invade this area and as a result, the matrix degenerates and leaving trabeculae of calcified cartilage (ZONE OF RETROGRESSION). OSTEOBLASTS then line the surface of these trabeculae and deposit layers of bone over the calcified cartilage (ZONE OF OSSIFICATION). In certain places you may see multinucleate osteoclasts which are resorbing portions of the newly formed bone (ZONES OF RESORPTION). 3. Bone (decalcified) (BN 5). In this cross-section of decalcified bone, identify the OUTER AND INNER CIRCUMFERENTIAL LAMELLAE, VOLKMAN’S AND HAVERSIAN CANALS, OSTEONS AND PERIOSTEUM. In addition, observe the OSTEOCYTES within their lacunae.
