Intamembranous Ossification

Front 1

intramembranous ossification

Back 1

forms bones of skull and claviacal

Front 2

step one

Back 2

mesenchyme condenses into layer of soft tissue with a dense supply of blood capilaries. the mesynchymal cells elarge and differentiate into osteogenic cells and regions of mesenchyme become a network of soft sheets called trabeculae

Front 3

step two

Back 3

osteogenic cells gather on trabaculae and differentiate into osteoblasts. osteoblasts deposit an organic matrix, osteoid tissue. as trabeculae grow thicker, calcium phosphate is deposited into matrix. some osteoblasts become osteocytes. mesenchyme close to the surface of trabaculae remain uncalcified, but become denser and more fibrous forming periosteium

Front 4

osteoid tissue

Back 4

soft collagenous tissue similar to bone, but lacks the minerals

Front 5

step three

Back 5

osteoblasts continue to deposite minerals, producing a honecomb of bony trabeculae. some trabeculae persist as spongey bone, while osteoclasts reabsorp and remodel others to form the marrow cavity

Front 6

step 4

Back 6

trabeculae at the surface continue to calcify until the spaces between them are filled in, converting the spongey bone to compact bone. gives rise to the sandwhich structure of flat bones

Front 7

summary

Back 7

1. mesenchym condenses into soft layer with blood capilaries. form osteogenic cells and trabeculae
2. osteogenic cells produce osteoid tissue. formation of osteocytes. surface mesenchye becomes dense and fibrous periostium
3. mineral deposition creates honecomb appearance of spongey bone. osteoclasts remodel some trabelcule to form marrow cavity
4. surface trabeculae contiune to calcify and form compact bone.

Front 8

trabeculae

Back 8

networks of soft sheets derived from mesenchyme

Front 9

broader sumamry

Back 9

1. mesenchyme=>osteogenic cells + trabeculae
2. osteoid tissue, osteocytes, periostium
3. honeycomb shape, spngey bone, marrow cavity
4. compact bone