Irregular bones in the human body are divided into the following two categories: the first major category is vertebrae, vertebrae are all the bones of the spine, such as cervical, thoracic, lumbar, sacral, caudal, etc., these bones belong to the range of irregular bones, such bones due to the extremely irregular shape and shape changes are relatively large, can not be classified into other categories, such as long bones, short bones, flat bones, so they are assigned to irregular bones. The second major category is the bone containing cavities called air-containing bone, such as the maxilla or sieve bone around the nasal cavity belong to this category, these bones are irregular in shape and its internal cavity, in the process of vocalization these bones can produce resonance, these parts of the cavity can also effectively reduce the weight of the bone.