For better understanding purposes, the external cranial base can be subdivided into four parts. Each is composed of different structures of the skull.

The anterior part is made of the palatine process (Read more!) and alveolar process (Read more!) of the maxillae and horizontal plates (Read more!) of the palatine bones. Both choanae (Read more!) mark the border between the anterior and middle parts.
The middle part is formed by the greater wings (Read more!), pterygoid processes (Read more!) and the body (Read more!) of the sphenoid, petrous part (Read more!) and squamous part (Read more!) of both temporal bones, and the basilar part (Read more!) of the occipital bone (Read more!).
The posterior part is mainly formed by the occipital bone.
Each lateral part of the external cranial base is made of the zygomatic arch (formed by the temporal and zygomatic bones), the greater wing (Read more!) of the sphenoid and the squamous part, tympanic part (Read more!) and mastoid part (Read more!) of the temporal bone.

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External cranial base (parts and bones)