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| The Surgical Technologist | SEPTEMBER 2017 398 and circulation. The sternum, made out of bone, consists of three parts: the upper piece or manubrium, the middle piece or gladiolus, and the lower piece, or the xiphoid process (or the appendix). The ribs are elastic arches of bone, with 12 on each side of the thoracic cavity. The first seven ribs, referred to as true ribs, each attach to the sternum with a piece of cartilage. The next five ribs (8-12) are called false ribs, with ribs 8-10 attaching by cartilage to the sternum via a com- mon costal cartilage. Ribs 11 and 12 are free at the anterior border and are called floating ribs. 2 The space in between the ribs is called intercostal spaces. Ribs are comprised of cancellous bone tissue and also have three sections: a pos- terior vertebral, anterior or sternal, and the shaft of the rib in between. In most places, the ribs are covered by the large mus- cle of the chest wall: specifically, the pectoralis major and minor anteriorly, and the latissimus dorsi, serratus posterior, trapezius and rhomboid muscles posteriorly. Furthermore, the scapula and its muscles cover the upper posterior ribs. There is relatively little muscle coverage of the ribs laterally, with the exception of the serratus anterior. For this reason, the ribs can be most easily palpated in the lateral area of the chest wall. There are a few bony landmarks that help with counting the ribs to delineate specific rib numbers. First, the second rib articulates anteriorly at the angle of the sternum. Next, the tip of the scapula is generally located over the 7th rib. Finally, the 11th and 12th ribs usually can be identified by palpation due to their lack of articulation with the ster- num anteriorly. The ribs are surrounded in muscle, including the dia- phragm, triangularis sterni, levatores costarum, infracos- tales and the internal and external intercostals. The internal and external intercostals depress and raise the ribs during respiration and work in concert with the diaphragm as the chief muscle for inspiration. The diaphragm is a fan-shaped muscle that lies obliquely in the upper third of the body trunk, 2 which is considered a dome-like structure due to it separating the floor of the thorax and the roof of the abdomen from the organs below. It is not only assists in breathing, but in expelling feces, urine and vomiting. Along the front, the muscle fibers of the diaphragm insert into the xiphoid process and run along the costal margin (the lower edge of the thoracic cage at the ribs) and laterally into ribs 6-12. Along the back, the fibers attach into the vertebrae at T12 and with two tendinous appendages – the right and left crus – downward into the lumbar vertebrae at L1 and L2. The diaphragm consists of muscular fibers and contains three openings to accommodate the aorta, the esophagus and the inferior vena cava. 1 The aortic opening lies in the very posterior aspect of the diaphragm, slightly to the left and at begin- ning of L1 between the right and left crus. The esophageal opening is located at the level of T10, while the opening for the inferior vena cava lies at T12. The diaphragm is sup- plied by the intercostal and phrenic nerves. During breathing, the diaphragm contracts and the vol- ume of thoracic cavity increases as the air is drawn into the lungs, creating negative pressure. The diaphragm, along with its tendons and nerves, acts as a stabilizing structure for the ribs and thoracic cage. When ribs are fractured, the design and function of breathing are compromised. The constant contraction and expanding movement causes instability and pain. The 11 pairs of external intercostals run from the lower border of each rib to the upper border of the rib below. They consist of muscle fiber and are supplied by the inter- costal nerves. The internal intercostals, also 11 pairs, begin at the ster- num and run in between the cartilages of the true ribs, and from the anterior border of the false ribs to the vertebral With the creation of a lower profile, the anatomically contoured plating systems have been designed to follow rib anatomy and provides for a better solution than wires and suture.