c. Role of Curvatures of Vertebral Column. As a whole, the vertebral column
has four curvatures. Two of these are concave to the front; two are concave to the rear.
As do the intervertebral discs, these curvatures function as shock absorbers for the
4-35. FUNCTIONS OF THE RIB CAGE
The thoracic cage consists of the ribs, the sternum, and thoracic vertebrae. The
12 pairs of ribs are attached posteriorly to the thoracic vertebrae. Anteriorly, the upper
10 pairs of ribs attach directly or indirectly (via costal cartilages) to the sternum.
a. Motion. Because of the segmentation of the thoracic cage into vertebrae and
ribs, motion can occur in the thoracic region of the body.
b. Costal Breathing. The special construction of the ribs and their costal
cartilages allows costal breathing to take place.
c. Protection. In addition, the rib cage encloses such vital structures as the
lungs, the heart, and the liver and gives them protection.
Section X. THE APPENDICULAR SKELETON
The appendicular skeleton consists of the bones of the upper and lower
4-37. THE GIRDLES
Each member is attached ("appended") to the axial skeleton by a skeletal
element called a girdle.
a. Pelvic Girdles. The girdle of each lower member is called the pelvic girdle.
Each pelvic girdle is attached firmly to the corresponding side of the sacrum. With their
ligaments, the two pelvic girdles and sacrum together form a solid bony circle known as
the bony pelvis.
b. Pectoral Girdles. The girdle of each upper member is called the pectoral
girdle. Unlike the pelvic girdles, each pectoral girdle is very loosely attached to the axial
skeleton. The sole attachment is by the sternoclavicular joint, which in turn is
constructed to increase the degrees of motion.