What is the cartilage model when referring to a 4 week old embryo?

Answer 1

The cartilage model in a 4-week old embryo is called an anlage, and the process is called endochondral bone formation. By the 8th week of gestation, osteoclasts begin removing the center to allow blood vessels to enter, as well as osteoprogenitor cells to develop.

Answer 2

cartilage model is always referring the pre-ossificated bone tissue which is first form in the cartilage medium.

As the embryo grows, ossification process will fill in the details of this mode with marrow cavity, osteoblasts, osterclasts, epiphysigeal plates and joins while the osteoblasts filling in the bone mess with calcium.