Histology of Bone & Ossification Vocab

Osteogenic (osteoprogenitor) cells -go through cell division, develop into osteoblasts; found in endosteum and inner portion of periosteum -assist in fracture repair Bone resorption -destruction of bone matrix by osteoclasts

Compact bone tissue consistency -few spaces Calcification -Hardening of bone tissue as salts are deposited into the collagen framework Compact bone tissue consistency -few spaces -dense matrix, supportive connective tissue -Calcium phosphate around collagen fibers

Compact bone tissue structure -osteons arranged in concentric rings, held together by lamellae

Perforating (Volkmann’s) canals -horizontal canals; perpendicular to central canal -carry blood vessels into bone and marrow Central (Haversian) canal -vertical canal, extending lengthwise through the bone -bring nerves/blood vessels into bone

Concentric lamellae -plate-like membrane Lacunae -wrapped around long bone; binds osteons together Lacunae -spaces between lamellae which contain osteocytes

Spongy bone tissue structure -does not contain osteons Canaliculi -Tiny channels projecting from lacunae; osteocyte’s fingerlike projections are held here Spongy bone tissue structure -does not contain osteons -consists of trabeculae -lots of spaces

Trabeculae -strands of bone that make up an irregular “meshwork”/”lattice work” with spaces

Ossification -the process of replacing other tissues with bone Intramembranous ossification (occurs in the dermis, Produces bones such as mandible and clavicle) -Osteogenic cells become osteoblasts -Osteoblasts secrete matrix -Osteoblasts become osteocytes -Salts/minerals added- bone hardens -Trabeculae fuse together forming spongy bone -Blood vessels grow in spaces -Red bone marrow forms

Endochondral ossification (bone replaces cartilage; most bones formed this way) -Chondrocytes in the center of hyaline cartilage enlarge, calcify, and die, leaving cavities in cartilage -Blood vessels grow around the edges of the cartilage and osteogenic cells begin to change to osteoblasts. Produces layer of superficial bone around shaft which becomes compact bone - Blood vessels enter the cartilage. Spongy bone develops at the primary ossification center in the shaft where bone tissue replaces cartilage. A marrow cavity is created. -Capillaries and osteoblasts enter the epiphyses creating secondary ossification centers - Epiphyses fill with spongy bone (no cavity in this region of the bone). On the ends, hyaline cartilage that remains is articular cartilage.

Epiphyseal line -When the cartilage of the epiphyseal plate (which allows for diaphysis of bone to increase in length) is replaced by bone, the epiphyseal line appears.

Bone remodeling -ongoing process -old bone tissue replaced by new bone tissue -also removed worn/injured bone to be replaced with new bone -osteoclasts/osteoblasts