In principle there are 23 cranial bones, including the facial and cerebral crania. The cranium is generally divided into four pieces: frontal, temporal, parietal and occipital, with four pieces on one side and a total of eight pieces on the left and right sides. In general, trauma to the parietal bone is easy to cause fracture, there are some to remove the frontal bone tissue, resulting in cranial defects. The skull includes the maxilla, nasal bone, and other bones totaling 15 pieces, which together add up to 23 pieces. The auditory bones are not included here. There are three pairs of auditory ossicles in the middle ear, which add up to 29 bones, but in principle they are not included.