Snell's Clinical Anatomy: Thorax, Part I (Thoracic Wall) PDF

20-year-old woman was the innocent victim of a {cavity}. She was particularly careful to avoid important ana- A street shoot-out involving drugs. On examination in the emergency department, the patient showed signs of severe hemorrhage and was in a state of shock. Her...

20-year-old woman was the innocent victim of a {cavity}. She was particularly careful to avoid important ana- A street shoot-out involving drugs. On examination in the emergency department, the patient showed signs of severe hemorrhage and was in a state of shock. Her tomic structures. The incision was made in the fourth left intercostal space along a line that extended from the lateral margin of the sternum pulse was rapid, and her blood pressure was dangerously to the anterior axillary line. The following structures were incised: low. A small entrance wound was noted about 1 cm wide in skin, subcutaneous tissue, pectoral muscles and serratus ante- the fourth left intercostal space about 3 cm from the lateral rior muscle, external intercostal musde and anterior intercostal margin of the sternum, but no exit wound. The left side of membrane, internal intercostal muscle, innermost intercostal her chest was dull on percussion, and breath sounds were musde, endothoracic fascia, and parietal pleura. The internal absent on that side of the chest. A chest tube was immedi- thoracic artery, which descends just lateral to the sternum and ately inserted through the chest wall. Because of the massive the interoostal vessels and nerve, must be avoided as the knife amount of blood pouring out of the tube, the attending phy- aJts through the layers of tissue to enter the chest. The cause of sician decided to enter the chest (thoracotomy). The physi- the hemorrhage was perforation of the left atrium of the heart cian carefully counted the ribs to find the fourth intercostal by the bullet. A clinician must have knowledge of chest wall space and cut the layers of tissue to enter the pleural space anatomy to make a reasoned diagnosis and institute treatment CHAPTER OUTLINE Overview Thorade Openings RadloaraPhlc Anatomy Olteology Thoracic Apertures Surface Anatmny Sternum lntercostal Spaces Anterior Chest Wall Ribs Ribs Vertebrae Muecles Diaphragm lntercostal Muscles Nipple Joints Diaphragm Apex Beat of Heart Sternal Joints Levatores Costarum Axillary Folds Joints of Heads of Ribs Serratus Posterior Muscles Posterior Chest Wall Joints of Tubercles of Orientation Lines Ribs Nerves Trachea Joints of Ribs and Costa! Branches Lungs Cartilages Pleura Joints of Costa! Cartilages with Vuculalure Heart Sternum Internal Thoracic Artery Thoracic Blood Vessels Rib and Costa! Cartilage Internal Thoracic Vein Manunary Gland Movements lntercostal Arteries and Veins 192  Osteology 193 LEARNING OBJECTIVES The purpose of this chapter is to review the basic anatomy respiration, including a comparison of the of the thoracic wall in order to understand normal roles of the diaphragm, thoracic cage, and ftmctional relationships and the basis for common injuries, thoracoabdominal muscles in normal respiration. pain, motor deficits, congenital defects, medical imaging, S. Trace the course of motor and sensory and general surface examination. innervation of the thoracic wall. Predict the functional consequences of lesions of individual 1. Identify the bones of the thoracic cage and their peripheral nerves. major features. Describe the functional aspects of 6. Trace the ftow of blood to and through the these structures. thoracic wall by describing the courses and 2. Identify the bony components, major supporting branching patterns of the major arteries and ligaments, and movements permitted at the joints veins. Identify the territories supplied and of the thoracic cage. drained by the major vessels. Note the main 3. Describe the structure of the thoracic wall, collateral routes, and describe the composition of including its layers and the contents of a typical significant anastomoses. intercostal space. Note the arrangement of the 7. Describe the pattern of lymphatic drainage intercostal muscles and neurovascular elements. of the thoracic wall, including the relationship Note collateral routes and major anastomoses of of this drainage to that of the axilla and arteries. breast. 4. Describe the development, structure, position, 8. Identify the major structures of the thoracic wall and actions of the diaphragm. Identify its in standard medical imaging. innervation, and indicate the segmental sources 9. Locate the surface projections and palpation and pathways taken by these nerves to reach points of the major thoracic structures in a basic the diaphragm. Describe the mechanics of surface examination. OVERVIEW each side of the thorax, between the lungs and the thoracic walls. The chest, or thorax (thora- ls Greek for "breastplate"; "chest"), is the region of the body between the neck OSTEOLOGY and the abdomen. It ls flattened In front and behind but rounded at the sides. Skin and muscles of the shoulder The thoracic skeleton fonns an osseocartilaginous, girdle cover the exterior of the thoracic wall, whereas cagelike unit that surrounds and protects the heart, parietal pleura lines its inner surface. The skeletal lungs, and adne:xa. It also covers all or parts of certain framework of the thoracic walls is referred to as the upper abdominal organs (e.g., liver, stomach, spleen, thoracic cage. This ts formed by the thoracic part of the kidneys). The thoracic cage ls a component of the a.xlal vertebral column posteriorly, the ribs and lntercostal skeleton and Is formed by the sternum, ribs, costal car- spaces laterally on either side, and the sternum and tilages, and thoracic vertebrae. costal cartllages anteriorly {Fig. 4.1). Superiorly, the thorax communicates with the neck, and Inferiorly, lt ls separated from the abdomen by the diaphragm. The Stemum thoracic cage protects the lungs and heart and provides The sternum (stem- is Greek for "breast"; "breast- attachment for the muscles of the thorax. upper extrem- bone") ls the elongate, flat bone that lies In the midline ity, abdomen, and back. of the anterior chest wall. The adult sternum consists The thoracic cavity can be divided into a median of three parts: manubrlum, body, and uphold proc:ea portion, called the medla.stlnum, and the laterally (see Fig. 4.1). placed pleurae and lungs. The lungs are covered The manubrlum. (manubrl- is Latin for "handle") is by a thin membrane called the visceral pleura, the upper part of the sternum. It articulates with the which passes from each lung at Its root {I.e., where body of the sternum at the manubrlosternal Joint, and the main air passages and blood vessels enter) to It also articulates with the clavicles and with the first the inner surface of the chest wall, where it is called costal cartilage and the upper part of the second costal the parietal pleura. In this manner, two membranous cartilage on each side. lt lies opposite the third and sacs called the pleural cav11ies are formed, one on fourth thoracic vertebrae (Fig. 4.2). The supra.sternal 194 CHAPTER 4 Thorax, Part I: Thoracic Wall Supraaternal notch I /.-_ Facetfor clavlcle ,Jj""°('.J-... ;--.,'ll.. / I.*~' ~ ,..,...... · -....... - o.., I _,,.... , ·. '( "' i' :\-,..,.. ff'"...,.~·~i·...,l.. ~..... - i, ,.1 ,.,,,,. Fa,.........,, for l./ ··.;..:..- ~: ·· :- : '-1"1' Greater tuberoslty found In the fifth left lntercostal space, 3.5 In. (9 cm) of humerus from the mldllne. If you have difficulty In finding the Inferior angle- 1 Spine of scapula of scapula , apex beat, have the patient lean forward ln the sitting Medial border position. Thoraci~ of scapula spine 89\len Lateral bon:fer In a female with pendulous breasts, the examining Twelfth Rih-- - mrlr1' fingers should gently raise the left breast from below as ' ofscapula Thoracic the intercostal spaces are palpated. B spine 12 Axillary Folds Figure 4.21 Surface landmarks of anterior (A) and The lower border of the pectoralis major muscle forms the anterior a:xlllary fold (see Figs. 4.19 and 4.20A). posterior (8) thoracic walls. This can be made to stand out by asking the patient to press a hand hard against the hip. The tendon of the latlsslmus dorsl muscle as it passes around the lower Diaphragm border of the teres major muscle forms the posterlor The central tendon of the diaphragm lies directly behind a:dllary fold (see Fig. 4.208). the xiphlstemal joint. In the midresplratory position, the summit of the right dome of the diaphragm arches Posterior Chest Wall upward as far as the upper border of the fifth rib in the The splnous proceaes of the thoracic vertebrae can midclavicular line, but the left dome only reaches as far be palpated In the posterior mldUne (Fig. 4.22; see also as the lower border of the fifth rib. Figs. 4.208 and 4.218). The index finger should be Nipple placed on the skin in the mldline on the posterior sur- face of the neck and drawn downward in the nuchal In the male, the nipple usually lies in the fourth inter- groove. The first spinous process to be felt is that of costal space about 4 in. (10 cm) from the midline. In the seventh cervical vertebrae (vertebra promlnena). the female, its position is not constant. However, the The overlapping spines of the thoracic vertebrae are T4 dennatome always crosses the nipple in both sexes below this level. A large ligament, the llgamentum. regardless of the form of the breast. nuchae, covers the spines of the Cl to 6 vertebrae. It should be noted that the tip of a splnous process of a Apex Beat of Heart thoracic vertebra Iles posterior to the body of the next The lower portlon of the left ventricle forms the apex vertebra below. of the heart. The apex of the heart being thrust forward The 8Capula (shoulder blade) ls Oat and triangular in against the thoracic wall as the heart contracts causes shape and ls located on the upper part of the posterior the apex beat. (The heart is thrust forward with each surface of the thorax. The 1Uperlor angle Iles opposite ventricular contraction because of the ejection of blood the spine of the second thoracic vertebra. The spine of from the left ventricle Into the aorta; the force of the the scapula is subcutaneous, and the root of the spine blood in the aorta tends to cause the curved aorta to lies on a level with the spine of the third thoracic verte- straighten slightly. thus pushing the heart forward.) bra The Inferior angle lies on a level with the spine of The apex beat can usually be felt by placing the flat of the seventh thoracic vertebra. 214 CHAPTER 4 Thorax, Part I: Thoracic Wall rO Clinical Notes Clinical Examination of Chest the alveoll or bronchi are diseased and filled with fluid, the nature of the breath sounds will be altered. The rate and As medical personnel, you will beexamining the chest to detect mythm of the heart can be confirmed by auscultation, and evidence of disease. Your examination consists of inspection, the various sounds produced by the heart and Its valves palpation, percussion, and auscultatton. lmpecdon shows the during the different phases of the cardiac cycle can be configuration of the cheat, the range of respiratory movement, heard. Detecting friction sounds produced by the rubbing and any Inequalities on the two sides. The type and rate of together of diseased layers of pleura or pericardium may respiration are aJso noted. Palpation enables the cltntc:lan be possible. to C