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23 terms

Bone Development - Ossification

Ossification
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Ossification
Process of bone formation
Intramembranous and Endochondral
The two methods of ossification in the fetus and young children
Intramembranous Ossification
the process of bone formation in the flat bones of the skull and most of the clavicle, where bone forms directly within mesenchyme arranged in sheetlike layers that resemble membranes
Osteoid Tissue
Soft collagenous matrix similar to bone but without minerals.
Mesenchyme
Embryonic connective tissue from which all tissues develop
First Stage of Intramembranous Ossification
condensation of mesenchyme into soft sheet permeated with blood capillaries; differentiation of cells into osteogenic cells, beginning of trabeculae
Second Stage of Intramembranous Ossification
Deposition of osteoid tissue and calcium phosphate by osteoblasts on mesenchymal surface; entrapment of first osteocytes and formation of periosteum
Third Stage of Intramembranous Ossification
Honeycomb of bony trabeculae formed by continued mineral deposition by osteoblasts; creation of spongy bone; osteoclasts resorb and remodel other trabeculae to form a marrow cavity
Fourth Stage of Intramembranous Ossification
Surface bone filled in by bone deposition, converting spongy bone to compact bone with spongy bone in the middle
Endochondral Ossification
the most common bone formation process, which involves the replacement of hyaline cartilage (developed by mesenchyme) with bone
Range for Endochondral Ossification
sixth week of fetal development though a person's 20s
Epiphyseal Plate
plate of hyaline cartilage between the epiphysis and diaphysis of a long bone in immature bone, serving as a growth zone for bone elongation through childhood and adolescence; growth center
Perichondrium
an outer covering of fibrous connective tissue that develops around the cartilage model during ossification
Chondrocyte
the only cells found in cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans
First Step of Endochondral Ossification
early cartilage model: mesenchyme develops into a body of hyaline cartilage, covered with a fibrous perichondrium, in the location of future bone; perichondrium produces chondrocytes for a time
Second Step of Endochondral Ossification
osteocytes not chondrocytes produced; formation of primary ossification center, bony collar, and periosteum
Primary Ossification Center
during endochondral ossificaiton, a region near the middle of the cartilage model where bone tissue replaces most of the disintegrating calcified cartilage
Third Step of Endochondral Ossification
vascular invasion; formation of primary marrow cavity, and appearance of secondary ossification center
Metaphysis
the region of transition from cartilage to bone at the end of the primary bone marrow cavity; synonymous with epiphyseal plate
Secondary Ossification Center
this develops in the epiphyses of bone during endochondral ossification; in longer bones is occurs at both ends, in shorter bones it occurs in only one epiphysis
Fourth Stage of Endochodral Ossification
formation of secondary marrow cavity in the epiphysis which expands out in all directions and is present at birth
Fifth Stage of Endochondral Ossificaton
epiphyses fill with spongy bone during infancy and childhood; cartilage limited to the articular cartilage covering each joint surface, and to epiphyseal plate separating the primary and secondary marrow cavities on one or both ends of the bone
Sixth Stage of Endochondral Ossificaton
all remaining cartilage in the epiphyseal plate is generally consumed and the gap between the epiphysis and diaphysis closes by the late teens and early twenties; primary and secondary marrow cavities unite into one; bone can no longer grow in length