Bone Formation/ Layers of Bone

First layer

Periosteum - the outer layer that contains blood vessels and cells

Second layer

Compact bone - next layer, smooth and hard, round bone cells, blood vessels

Third layer

Cancellous - next layer, spongy and protects bone marrow

Fourth layer

Bone marrow - the inner most layer very thick , jelly and makes the blood cells

step 1

Soft cartilage when fetus

Step 2

Ossification- osteoblast migrate to center of cartilage and begin to deposit minerals to form hard bone

step 3

by 8th week of pregnancy outline of skeleton formed

step 4

Periosteum- outermost layer forming containing nerves and vessels

step 5

osteoblast gets trapped within bone making them no longer able to travel