Answer:
They are formed by the Membranous ossification.
Explanation:
Cranial bones , clavicles and the flat bones on the face are usually formed from the membranous ossification.
The process begins when the mesenchymal cells of the embryonic skeleton come together and begin to differentiate to form specialized cells .
They will differentiate into capillaries while others will form steogenic and then osteoblasts .
Eventually they will be spread out to form born tissues early osteoblasts will appear in ossification which is a cluster center .
They later go through a process of hardening known as calcified matrix.
