THE FRAMEWORK OF THE BODY 



31 



of the ribs. In addition, the skeleton includes two so-called "girdles" and 

 their appendages — an upper one, the shoulder or pectoral girdle, to which 

 the arms are attached, and a lower one, the hip or pelvic girdle, bearing 

 the legs. These two girdles and their appendages make up the appendic- 

 ular skeleton. 



The axial skeleton. The axial skeleton forms the longitudinal or 

 vertical axis of the body. The skull consists of two main parts, the cranium 

 or brain case and the bones of the face. The former is a rigid bony box, 



frontal bone 



sphenoid 

 bone 



nasal bone 



lachrimaj, 

 bone 



zygomatic 

 arch 



maxilla 



parietal 

 one 



occipital 

 bone 



poral 



Fig. 3.3. The human skull. 



averaging between 1,200 and 1,500 cc. in capacity, which, in life, is 

 completely filled by the brain, its membranes, and the thin layer of fluid 

 that insulates the brain from direct attachment to or contact with the 

 bony walls. The bones of the face surround the mouth and nasal openings, 

 form the lower parts of the eye sockets and the bony partition between 

 the nose and mouth cavities. Except for the strongly hinged lower jaw 

 and three pairs of tiny ear bones, all the bones of the skull are immovable 

 and are fused into a single rigid structure by strong, dovetailed sutures 

 between the various bones. 



Altogether, the skull comprises some 22 bones, of which 8 pertain to 

 the cranium and 14 to the facial portion. Sixteen lower teeth are borne 



