The skull is composed of 23 irregular bones, including 15 facial cranial bones and 8 cerebral cranial bones. The facial cranial bones enclose the orbits, nasal cavity and oral cavity, one on each side, including the maxilla, nasal bone, lacrimal bone, zygomatic bone, palatine bone, inferior turbinate bone, plow bone, mandible and free hyoid bone. The cranial skull consists of the skull cap and the skull base. The skull cap includes the frontal, parietal, occipital, and temporal bones, as well as some of the zygomatic bones and the large wing of the butterfly, which are connected together by the coronal, sagittal, herringbone, and squamous sutures. The cranial base bones include the sieve, butterfly and occipital bones, which together form the anterior, middle and posterior cranial fossa structures.