4 Flat bones are relatively thin, and expanded in two dimensions. 5 Sesamoid bones resemble a sesame seed and are developed along the course of tendons to reduce friction or change the course of tendons. 6 Pneumatic bones contains air spaces that communicate with the exterior. Found in the skull. 7 Irregular bones are unpaired bones located in the median plane, e.g. vertebrae and sternebrae, etc.
Irregular bones are important for protection, support and muscle attachment.
This includes almost all bones, except those of the limbs. It functions in protection of the brain, supports many of the sense organs and forms passages for the beginning of the digestive and respiratory system. The skull is composed of a large number of bones which are joined together by joints called sutures. The large number of bones, and their slightly differing shapes and sizes in various animals accounts for the difference in the shape of heads of individual animals. The vertebrae in the various regions differ in the degree of development of the various parts.