Intramembranous and Endochondral Ossification

There are two types of bone development: intramembranous and endochondral ossification or osteogenesis. Regardless of the ossification process, the histological structure of the bone is the same.

• Intramembranous ossification gives rise to membrane bones, these being the flat bones of the skull and parts of the mandible. This process involves the deposition of bone matrix (osteoid) directly in regions ("membranes") of embryonic mesenchyme. Click here, or look at the image to the right, for a full-size, printable version of the picture detailing this process.

• Bones of the extremities, pelvis, and vertebral column (cartilage bones) are formed by endochondral ossification. This process involves the replacement of a hyaline cartilage model with bone beginning during fetal development and ending in late adolescence.
  
   
• Let's look at some examples.