Which skull bones form by endochondral ossification?

Which skull bones form by endochondral ossification?

• A. Bones of the Skull Base
• B. Most Other Skull Bones
• C. Facial Bones
• D. Mandible

Answer: (A)

Endochondral ossification uses a cartilage template that is replaced by bone, and in the skull this process applies to the bones forming the cranial base. Those base bones originate from a cartilaginous neurocranium that provides a scaffold for growth, and they ossify endochondrally as development proceeds. In contrast, most other skull bones—such as the flat bones of the skull vault and the facial bones—form directly from mesenchyme through intramembranous ossification, without a cartilage stage. The mandible is also mainly formed by intramembranous ossification, with the condyle sometimes showing endochondral-like development, but the primary pattern for the mandible is intramembranous. Thus, the skull base bones are the ones that form by endochondral ossification.

Endochondral ossification uses a cartilage template that is replaced by bone, and in the skull this process applies to the bones forming the cranial base. Those base bones originate from a cartilaginous neurocranium that provides a scaffold for growth, and they ossify endochondrally as development proceeds. In contrast, most other skull bones—such as the flat bones of the skull vault and the facial bones—form directly from mesenchyme through intramembranous ossification, without a cartilage stage. The mandible is also mainly formed by intramembranous ossification, with the condyle sometimes showing endochondral-like development, but the primary pattern for the mandible is intramembranous. Thus, the skull base bones are the ones that form by endochondral ossification.