Bone Development - Ossification

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23 terms · Ossification

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

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