Copyright Goodheart-Willcox Co., Inc. Chapter 5 The Skeletal System 141 • Body—the remainder of the bony portion of the sternum • Xiphoid process—projection at the lower end of the sternum The sternum has three notable bony features. The jugular notch is a readily palpable indentation at the superior end of the sternum. The sternal angle is a slightly elevated transverse ridge occurring where the body of the sternum joins the manubrium at a small angle. The xiphisternal joint is, as the name suggests, the junction between the sternal body and xiphoid process at the level of the ninth thoracic vertebrae. There are 12 pairs of ribs in the thoracic cage, as shown in Figure 5.19. The first seven pairs (1–7) attach directly to the sternum and are, therefore, called true ribs. The next three pairs of ribs (8–10) are called false ribs because they have cartilaginous attachments to the cartilage of the seventh rib, rather than attaching directly to the sternum. The lowest two pairs of ribs (11–12) are known as floating ribs, because they do not attach to bone or cartilage in front of the body. SELF CHECK 1. List the five regions of the vertebral column, from upper to lower. 2. What is the functional purpose for the increasing size of vertebrae from the cervical region down to the lumbar region? 3. What is the function of the intervertebral discs? Thoracic Cage The ribs, sternum, and thoracic vertebrae are collec- tively known as the thoracic cage, or bony thorax, because together they form a protective, bony “cage” that surrounds the heart and lungs in the thoracic cavity, as shown in Figure 5.19. The breastbone, or sternum, includes three regions: • Manubrium—the upper portion of the sternum it has articulations to the left and right bones of the clavicle, as well as to the first and second ribs Scoliosis Kyphosis Lordosis Lateral deviation of spine Exaggerated lumbar curve Accentuated thoracic curve © Body Scientific International Figure 5.18 Three types of abnormal spinal curvature.