Snell's Clinical Anatomy Chapter 5 - Thorax. Part II (Thoracic Cavity) PDF

54-year-old woman visited ~e emergency department The severe nature of the pain and its radiation to the back A with a complaint of a sudden excruciating knifelike pain in the front of her chest During the course of examina- tion, she said she could also feel the pain in her...

54-year-old woman visited ~e emergency department The severe nature of the pain and its radiation to the back A with a complaint of a sudden excruciating knifelike pain in the front of her chest During the course of examina- tion, she said she could also feel the pain in her back between made a preliminary diagnosis of aortic dissection a strong possibility. Myocardial infarction commonly results in referred pain down the inner side of the arm or up into the neck. the shoulder blades. On dose questioning, she said she felt Pain impulses originating in a diseased descending tho- no pain down the arms or in the nec:k.. Her blood pressure was racic aorta pass to the central nervous system along the 200/110 mm Hg in ~e right arm and 120/80 mm Hg in the left path of sympathetic nerves and are then referred along the arm. somatic spinal nerves to the skin of the anterior and posterior The evaluation of chest pain is one of the most common chest walls. In this patient, the aortic dissection had partially problems facing an emergency physician. The cause can blocked the origin of the left subclavian artery, which would vary from ~e simple to one of life-threatening proportions. explain the lower blood pressure recorded in the left arm. CHAPTER OUTLINE Overview Serous Pericardium Thoracic Duct Osteology Perlcardlal Sinuses Right Lymphatic Duct Thorade Cavity Nerve Supply Thorade Nerves Mecllasdnum Heart Vagus Nerves Superior Medtastlnwn Orlentatlon Phrenic Nerves Inferior Medlastlnum Heart Structure Sympathetic Trunks Heart Nerve Supply Pleurae Heart Arterial Supply Eeophagus Layers and Cavity Heart Venous Drainage Blood Supply Nerve Supply Heart Action Lymph Drainage Nerve Supply Lower Respiratory Tract Large Thorade Arteries Trachea Aorta Thymus Broncht Pulmonary Trunk Blood Supply Lungs Large Thorade Veins Radlograpblc Anatomy Lobes and Fissures Brachtocephallc Veins Posteroantertor Radiograph Bronchopubnonary Segments Superior Vena Cava Right Oblique Radlograph Blood Supply Azygos Veins Left Oblique Radlograph Lymph Drainage Inferior Vena Cava Bronchography and Contrast Nerve Supply Pulmonary Veins Visualization of the Esophagus Mechanics of Respiration Coronary Angiography lboractc Lymphattcs Computed Tomography Scanning Pericardium Thoracic Wall Fibrous Pericardium Medlastinum 218  Overview 219 LEARNING OBJECTIVES The purpose of this chapter is to review the basic anatomy 7. Describe the gross structure of the heart, of the thoracic cavity in order to understand normal including the fibrous cardiac skeleton. ftmctional relationships and the basis for common injuries, 8. Trace the course of blood flow through the pain, motor deficits, congenital defects, medical imaging, right and left sides of the heart. Identify and general surface examination. the internal structures of each chamber and the location and structure of each of the 1. Identify the major subdivisions of the thoracic valves. cavity and describe their contents. Identify the 9. Identify the elementary sounds of the normal subdivisions of the mediastinum and describe heart. Relate these to the flow of blood their contents. through the heart and the actions of the cardiac 2. Identify the major longitudinal structures valves. (e.g., trachea, esophagus, vagus nerves, phrenic 10. Identify the anatomical and auscultation nerves, aorta, sympathetic networks, azygous proJections of each of the cardiac valves onto the system, thoracic duct) running through the body surface. thoracic cavity, and describe their courses and 11. Trace the low of blood through each of the maJor relationships. coronary vessels. Identify which vessels supply 3. Identify the parietal and visceral pleurae, their the main Oow to and drainage from each of the different components, the pleural recesses, and chambers and the lnterventrlcular septum and the boundaries of the pleura in projection onto possible anastomoses and collateral vascular the body surface. pathways. 4. Identify and differentiate the right and left lungs, 12. Describe the conducting system and extrinsic including their lobes and fissures. Identify the Innervation of the heart. impressions made on the surfaces of each lung by 13. Trace the low of blood from the thoracic the major surrounding structures. walls and cavity to the heart by describing 5. Identify the primary, secondary, and tertiary the formation and courses of the caval and branches of the bronchial tree. Identify the azygos venous tracts. Indicate anastomoses and bronchi and the pulmonary arteries and collateral connections between these and other veins at the hilar surface of each lung. Define tracts and discuss the clinical significance of a bronchopulmonary segment and relate such connections. such segmentation to the organization of the 14. Trace the primary drainage routes of lymph from bronchial and vascular trees. the organs and walls of the thoracic cavity to the 6. Identify the parietal and visceral pericardia, points of venous connection. their relationship to the parietal pleurae and 15. Identify the major structures of the thorax In diaphragm, and their projections onto the body standard medical Imaging. surface. OVERVIEW Osteology The thoracic cage and the diaphragm bound the The thoracic skeleton forms an osseocartllaginous, thoracic cavity. However, the thoracic cavity Is much cageltke unit that encloses the thoracic cavity and smaller than the limits of the thoracic cage because surrounds and protects the contained heart, lungs, the diaphragm. deeply lnvaginates the lower margins and adnexa. It also covers all or parts of the upper of the thoracic cage. Also, the cavity extends upward abdominal organs (e.g., liver, stomach, spleen, kJdneys). Into the root of the neck about one fingerbreadth above The thoracic cage is a component of the axial skeleton the clavicle on each side (see Fig. 5.5). The diaphragm and is formed by the sternum, ribs, costal cartllages, ls the only structure (apart from the pleura and the and thoracic vertebrae. Details of the thoracic skeleton peritoneum) that separates the thoracic from abdomi- are provided in Chapters 2 (vertebrae) and 4 (sternum, nal viscera. ribs, and costal cartilages). 220 CHAPTER 5 Thorax, Part II: Thoracic Cavity Thoracic Cavity The mediasttnwn Is divided into superior and hafe.. The thoracic cavity can be divided into a median dor mecllaltfna by an imaginary plane passing from the partition, called the meclludnum, and the laterally sternal angle anteriorly to the lower border of the body placed pleurae and lungs {Figs. 5.1to5.3). Athin, serous of the fourth thoracic vertebra posteriorly (see Fig. 5.2). pleural membrane covers each lung, passes from each This plane is a noteworthy landmark In that It marks lung at Its root (I.e., where the main air passages and several key structures. From anterior to posterior, these blood vessels enter}, and continues onto the Inner sur- are the: face of the thoracic wall {Fig. 5.4). This arrangement of Joint between the manubrlum and body of the the pleura forms two independent membranous sacs sternum called the pleural cavlliea. one on each side of the tho- Second costostemal joint rax, between the lungs and the thoracic walls. Demarcation between the ascending aorta and the arch of the aorta Demarcation between the arch of the aorta and the MEDIASTINUM descending thoracic aorta The mediastinum is the area between the sternum, Bifurcation of the trachea the two pleural cavities, and the vertebral column Level of the left primary bronchus {Figs. 5.1 and 5.3). Though thick, it is a movable T4 intervertebral disc partition that extends superiorly to the thoracic out- The inferior mediastinum is further subdivided let and the root of the neck and inferiorly to the into the middle medludnnm, which consists of diaphragm. It extends anteriorly to the sternum and the pericardium and heart; the anterior medlud- posteriorly to the vertebral column. It contains the num, which ls a space between the pericardium and remains of the thymus, the heart and large blood ves- the sternum; and the posterior mecllastlnum, which sels, the trachea and esophagus, the thoracic duct and lies between the pericardium and the vertebral lymph nodes, the vagus and phrenic nerves, and the column. sympathetic trunks. Right lung, upper lobe-..._ Left oblique ftssure Right oblique fissure Right lung,~ lower lobe · Visceral pleura Pleural space Figure 5.1 Cross section of the thorax at the level of the eighth thoracic vertebra. Note the arrangement of the pleura and pleural cavity (space) and the fibrous and the serous pericardia. Recall that cross sections are normally viewed from below and that the observer's right is the subject's left.  Mediastinum 221 Superior mediastinum Middle medlastfnum Inferior m&dlaslfnum Xlphok:I process Figure 5.2 Subdivisions of the medi&$tinum. Thoracic wall For purposes of orientation, it is convenient to remember that the major mediastinal structures are arranged in the following order from anterior to posterior. Figure 5.4 Formation of the lungs. Note that each lung bud invaginates the wall of the c:oelomic cavity and then grows to fill a greater part of the cavity. Note also that the lung is covered with visceral pleura and the thoracic: wall is lined with parietal pleura. The original coelomic: cavity is reduced to a slitlike space called the pleural cavity as a result of the growth of the lung. Costa! pleura (parletal pleura) Superior Mediastinum (1) Thymus, (2) large veins, (3) large arteries, (4) trachea. (5) esophagus and thoracic duct, and (6) sym- pathetic trunks. The superior mediastlnwn ls bounded in front by the manubrlum sterni and behind by the first four thoracic vertebrae (see Flg. 5.2). Inferior Mediastinum / (1) Thymus, (2) heart within the pericardium with the Dlaphragmalfc pleura phrenic nerves on each side, (3) esophagus and thoracic (parietal pleura) duct, (4) descending aorta, and (5) sympathetic trunks. The inferior mediastinum is bounded in front by the Figure 5.3 Pleurae from above and in front. Note the body of the sternum and behind by the lower eight tho- position of the mediastinum and the hilum of each lung. racic vertebrae (see Fig. 5.2). 222 CHAPTER 5 Thorax, Part II: Thoracic Cavity rO Clinical Notes Deflection of the Mediastinum Mediastinal Tumors or Cysts In the cadaver, the medla.stinum is an inflexible, fixed Because many vital structures are crowded together structure because of the hardening effect of the preserving within the mediastinum, their functions can be interfered fluids. However, ln the living, lt ls very mobile; the lwtgs, with by an enlarging tumor or organ. A tumor of the heart, and large arteries are in rhytlunlc pulsation, and the left lung can rapidly spread to involve the mediastlnal esophagus distends as each bolus of food passes through it. lymph nodes, which on enlargement may compress H air enters the pleural cavity (a condition called the left recurrent laryngeal nerve, producing paralysis pneumothoru), the lung on that side immediately collapses of the left vocal fold. An expanding cyst or tumor can and the mediastinum is displaced to the opposite side. This partially occlude the superior vena cava, causing severe condltlon reveals itself by the patient being breathless and congestion of the veins of the upper part of the body. In a state of shock; on examination, the trachea and the Other pressure effects can be seen on the sympathetic heart are displaced to the opposite side. trunks, phrenlc nerves, and sometimes the trachea, main bronchi, and esophagus. Mediastinitis Mediastinoscopy The structures that make up themediastinum are embedded In loose connective tissue that ls continuous with that of Medlastlnoscopy ls a dlagnostlc procedure whereby the root of the neck Thus, It Is possible for a deep infection speclmens of tracheobronchlal lymph nodes are obtained of the neck to spread readily Into the thorax, producing a without opening the pleural cavities. A small Incision is medlastlnitls. Penetrating wounds of the chest involving made in the mldHne in the neck just above the suprasternal the esophagus may produce a mediastinitis. ln esophageal notch, and the superior mediastinum is explored down to perforations, air escapes Into the connective tissue spaces the region of the bifurcation of the trachea. The procedure and ascends beneath the fascia to the root of the neck, can be used to determine the diagnosis and degree of producing IUbcutmeou emph}9e11Ml. spread of carcinoma of the bronchus. PLEURAE and the larger thoracic cavity.) The pleural cavity normally contains only a small amount of tissue fluid, The paired pleurae and lungs lie on either side of the the pleural fluid. Pleural fluid covers the surfaces of medlastlnum. within the thoracic cavity (see Fig. 5.3). the pleura as a thin film, which causes surface ten- Each pleural membrane has two parts: a parletal layer sion adhesion of the pleural layers and permits them and a visceral layer. The parietal layer lines the tho- to move on each other with minimal friction. Thus, racic wall, covers the thoracic surface of the diaphragm the pleural cavity is a potential space under normal and the lateral aspect of the mediastlnum, and extends conditions and Is discernible only under abnormal into the root of the neck to Une the undersurface of conditions (e.g., when the lung is displaced by air or the suprapleural membrane at the thoracic outlet. The excess nuld). visceral layer completely covers the outer surface of For purposes of description, the parietal pleura the lung and extends into the depths of the interlobar ls dlvlded according to the region in which it Iles or fissures (Figs. 5.5 and 5.6; also see Figs. 5.1, 5.3. and 5.4). the surface that lt covers (see Figs. 5.3 and 5.5). The It is thinner than the parietal layer. cervical pleura (cupula) extends up into the neck, lining the undersurface of the suprapleural membrane Layers and Cavity (also see Fig. 4.8). It reaches a level of 1 to 1.5 in. The two layers are continuous with one another via a (2.5 to 4 cm) above the medial third of the clavicle. cuff of pleura that surrounds the structures entering The costal pleura lines the inner surfaces of the ribs, and leaving the lung at the hllum of each lung (see the costal cartllages, the intercostal spaces, the sides Figs. 5.3 to 5.5). This cuff hangs down as a loose fold of the vertebral bodies, and the back of the sternum. called the pulmonary ligament and allows for move- The diaphragmatic pleura covers the thoracic surface ment of the pubnonary vessels and large bronchi during of the diaphragm. In quiet respiration, the costal and respiration (see Fig. 5.5). diaphragmatic pleurae are In apposition to each other The parietal and visceral layers of pleura are sepa- below the lower border of the lung. In deep Inspiration, rated from one another by a slltllke space, the pleural the margins of the base of the lung descend, and the cavity (see Figs. 5.3 and 5.4). (Clinicians are increas- costal and diaphragmatic pleurae separate. This lower ingly using the term pleural tpace instead of the ana- area of the pleural cavity into which the lung expands tomic:: term pleural cavity. This is probably to avoid the on inspiration is referred to as the costodlaphrag- confusion between the pleural cavity [slitlike] space ma!lc receu (see Figs. 5.4 and 5.5). The mMlatdlnal  Pleurae 223 Costal plE!(lra Left lung (parietal pleura) Diaphragmatic pleura (parietal ple\lra) Figure 5.5 Different areas of the parietal pleura. Note the cuff of pleura (dotted lines) that surrounds the structures forming the root of the left lung at the hilum. The parietal and visceral layers of pleura become continuous here. Arrows indicate the position of the costodiaphragmatic recess. pleura covers and forms the lateral boundary of the During inspiration and expiration, the anterior borders mediastinum. It reflects as a cuff around the vessels of the lungs slide in and out of the recesses. and bronchi at the hilum of the lung and here becomes The surface projections of the lungs and pleurae are continuous with the visceral pleura. Thus, each lung described in Chapter 4. lies free except at its hilum, where it is attached to the blood vessels and bronchi that constitute the long root. During full inspiration, the lungs expand Nerve Supply and fill the pleural cavities. However, during quiet The pleural layers are illllervated differently despite lnsplratlon, the lungs do not fully occupy the pleural being a continuous membrane. Somatic afferent nerves cavities at four sites: the right and left costodlaphrag- supply the parietal pleura {Fig. 5.7), which is sensitive matlc recesses and the right and left costomediastlnal to paln, temperature, touch, and pressure: recesses. The intercostal nerves segmentally supply the costal The coetodlaphragmatlc l'ece8le8 are slltllke spaces pleura. between the costal and diaphragmatic parietal pleurae The phrenlc nerve supplies the medlastlnal pleura. that are separated only by a capillary layer of pleural The phrenic nerve supplles the diaphragmatic pleura fluid. During inspiration, the lower margins of the lungs over the dome, and the lower lntercostal nerves sup- descend into the recesses. During expiration, the lower margins of the lungs ascend so that the costal and ply the periphery of the diaphragmatic pleura. diaphragmatic pleurae come together again. Visceral afferent nerves supply the visceral pleura, The costomedlasdnal recesses are situated along the which Is sensitive to stretch but Is Insensitive to com- anterior margins of the pleura. They are slltllke spaces mon sensations such as pain and touch. These nerves between the costal and medlastlnal parietal pleurae, run In company with autonomic nerves from the pulmo- which are separated by a capillary layer of pleural fluid. nary plexus (see Fig. 5.7). 224 CHAPTER 5 Thorax, Part II: Thoracic Cavity lnfrahyold muaclee Left common carotid artery Left internal jugular vein Internal thoracic artery Rightvagus nerve 1-~~~:~~==t::LLeftvagus nerve ' Left subclavian artery Cervical dome of pleura Left mcummt laryngeal nerve First thoracic nerve A Thoracic duct sympathetic trunk Esophagus Right lung Left lung B Esophagus Figure S.6 Cross sections of the thorax. A. At the thoracic inlet. B. At the fourth thoracic vertebra. Phrenic nerves ,.(C3, C4, and C5).,..,.,_, ,,. Figure 5.7 Diagram showing the innervation of the pari- etal and visceral layers of pleura.  Lower Respiratory Tract 225 Q Clinical Notes Pleural Fluid Pleurisy The pleural cavity normally contains 5 to 10 mL of clear Inflammation of the pleura (pleuriU.orpleurisy), secondary fluid, which lubricates the apposing surfaces of the visceral to inflammation of the lung (e.g., pneumonia), results in and parietal pleurae during respiratory movements. ln11ammatory exudate coattng the pleural surfaces, which Hydrostatic and osmotic pressures stimulate formation causes roughening of the surfaces. This roughening of the fluid. Because the hydrostatic pressures are produces frtctlon, which can be heard with the stethoscope greater in the capillaries of the parietal pleura than in the as a ple-ar.l rub on inspiration and expiration. Fibroblasts capillaries of the visceral pleura (pulmonary circulation), often invade the exudate, resulting in deposition of collagen the capillaries of the visceral pleura normally absorb the and format.ion of pleural adhealona that bind the visceral pleural fluid. Any condltlon that Increases the production of pleura to the parietal pleura. the fluid (e.g., Inflammation, malignancy, congestive heart disease) or Impairs the drainage of the fluid (e.g., collapsed Pneumothorax,, Empyema, and Pleural Effusion lung) results In abnormal accumulation of fluid, called a pleural effwdon. The presence of 300 mL of fluid in the Air can enter the pleural cavity from the lungs or through costodlaphragmatlc recess In an adult ls sufficient to enable the chest wall (pneumothorax) as the result of disease or Its clinical detection. The clinical signs Include decreased lnJury (e.g., lnterstltlal lung disease, gunshot wounds). In lung expansion on the side of the effusion, with decreased the old treatment of tuberculosis, air was purposely lDJected breath sounds and dullness on percussion over the effusion Into the pleural cavity to collapse and rest the lung. This (Flg.5.8). was known as artlftclal pneumothorax. A..,ontaneou. poeumotborax Is a condition In which air enters the pleural cavity suddenly without its cause being immediately apparent. lnvesUgatlon usually reveals that air has entered.----Trachea from a diseased lung and a bulla (bleb) has ruptured. dlsplaced to left Wounds that penetrate the thoracic wall (e.g., stab wounds) may pierce the parietal pleura so that the pleural cavity is open to the outside air. This condltlon ts called open Collapsed pneumolhoru. Each time the patient inspires, it is possible right lung to hear a!r under atmospheric pressure being sucked Into the pleural cavity. Sometlmes, the clothing and the layers of the thoracic wall combine to form a valve so that air enters on inspiration but cannot exit through the wound. In these circumstances, the air pressure builds up on the wounded sideand pushes themediastinum toward the opposite side. Jn this situation, a collapsed ltmg ls on the injured side, and the opposite lung Is compressed by the deflected medlastlnum. Serous This dangerous condition Is called a temlon paeumoeboru. fluid Air in the pleural cavity associated with serous ftuid is known as hydropneamothorax. associated with pus Pleural effusion as pyopneumothorax, and associated with blood as hemopneumothoru.. ln hemopneumothorax, trauma to the chest may result In bleeding from blood vessels In the chest Figure 5.8 A case of a right-sided pleural effusion. wall, from vessels In the chest cavity, or from a lacerated The mediastinum is displaced to the left, the right lung. A collection of pus (without air) In the pleural cavity is called an empyema. The presence of excess serous fluid lung is compressed, and the bronchi are narrowed. in the pleural cavity ls referred to as a pleural effUllon (see Auscultation would reveal only faint breath sounds over Fig. 5.8). Fluid (serous, blood, or pus) can be drained from the compressed lung and absent breath sounds over the pleural cavity through a wide-bore needle, as described fluid in the pleural cavity. In Chapter 4 (see Needle Thoracostomy). LOWER RESPIRATORY TRACT Trachea The respiratory tract (respiratory tree) ts the network The trachea ls a mobtle cartilaginous and membranous of passageways that supplies air to the lungs. The tube (Figs. 5.10 to 5.12; also see Fig. 5.9). It begins in upper respiratory 1ract Includes the nasal passages the neck as the continuation of the larynx at the lower and sinuses. pharynx, larynx, and upper portion of the border of the cricoid cartilage at the level of the sixth trachea. The lower respiratory tract (1racheobron- cervical vertebra. It descends in the midline of the nedc. ddal tree) includes the lower portion of the trachea, In the thorax, the trachea runs through the superior the bronchi, and the bronchioles (Fig. 5.9). mediastinum, in approximately the midline. It ends by 226 CHAPTER 5 Thorax, Part II: Thoracic Cavity Left principal bronchus Respirator bronchiole Alveolus Figure 5.9 The lower respiratory tract, including the trachea, bronchi, bronchioles, alveolar duets, alveolar sacs, and alveoli. Note the path taken by inspired air from the trachea to the alveoli. dividing into right and left principal (main) bronchi at free ends of the cartilages. The posterior discontinuity the level of the sternal angle (opposite the disc between permits the esophagus to expand Into the trachea dur- the fourth and fifth thoracic vertebrae). During expira- ing swallowing. tion, the bifurcation rises by about one vertebral level The relations of the trachea ln the neck are described and during deep inspiration may lower as far as the in Chapter 12. sixth thoracic vertebra. In adults, the trachea is about The relations of the trachea in the superior medlasti- 4 1/2-in. (11.25-cm) long and 1 in. (2.5 cm) in diameter. num of the thorax are as follows: U-shaped bars (tracheal rings) of hyaline cartilage embedded in the tracheal wall support and maintain Anteriorly: The sternum, the thymus, the left bra- the patency of the trachea (see Fig. 5.9). The trachee.- chlocephallc vein, the origins of the brachlocephalic 118 moscle (a smooth muscle) connects the posterior and left common carotid arteries, and the arch of the aorta (see Figs. 5.6A, 5.10, and 5.30)  Lower Respiratory Tract 227 Tractiea Right upper bronchus Bractliocephalic _ _ ~~~frJ.:::--- artery Arch of aorta1-----.1."""- Rtght prfnclpal bronchus Figure 5.11 Relationship of the pulmonary arteries to the bronchial tree. Stomacti A Csrlna B Left prfnclpal bronchus Figure S.10 Thoracic part of the trachea. A. Note that the right principal bronchus is wider and is a more direct continuation of the trachea than the left. B. The bifurcation of the trachea as viewed from above. Posteriorly: The esophagus and the left recurrent laryngeal nerve (see Fig. 5.6A) Right llcle: The azygos vein, the right vagus nerve, and the pleura (Figs. 5.13A and 5.14A; also see Fig. 5.6) Figure 5.12 A plastinated specimen of an adult trachea, left llde: The arch of the aorta. the left common principal bronchi, and lung. Some of the lung tissue has carotid and left subclavian arteries, the left vagus been dissected to reveal the larger bronchi. Note that the and left phrenic nerves, and the pleura (see Figs. 5.6, right main bronchus is wider and a more direct continua- 5.138, and 5.14B) tion of the trachea than the left main bronchus. 228 CHAPTER 5 Thorax, Part II: Thoracic Cavity Esophagus Right brachiooephalic vein \fi'~-"lt------ Right phrenlc nerve Azygos vein -7'1'~~~~~.m -. l\"i~lt-l!H--- Superior vena cava Right bronchi -~~~~~L~M~~....,""._.-:-""""-~ Pulmonary veins Greater splanchnic nerve l.e$ser splanchnic nerve A Left brachiocephalic vein. Left pulmonary artery Left bronchi Left ventricle covered by pericardium --He- - Left pulmonary veins Descending aorta ~~~~'IP:-- Greater splanchnlc nerve ~~~'-1-- Diaphragm B Esophagus Figure 5.13 Lateral views of the mediastinum. A. Right side. B. Left side.  Lower Respiratory Tract 229 Right subdavlan vein Sympathettc Right clavicle ght subcfavius CutrU usele Azygosve temal thoracic 1ery lntercostal llE 1perfor vena cava BC:endlng aorta Right bror Pulmonary"' Rightabium Greater spland nc Inferior vena < light cupola of liaphragm 1NTERIOR vul costal cartilage Sympatt'letic Left aubclavl trunk artt Leftvagus Leftcommc nerve carotid arte1 Descending aorta Arch of aorta Left auricle Pulmonary tri Right ventrlc Left phrenic nerve ANTERIO.eft ventricle Apexof hel.eft cupola of iaphragm Figure 5.14 Dissection ofthe mediastinum. The lungs, pericardium, and costal parietal pleura have been removed. A. Right side. B. Left side. 230 CHAPTER 5 Thorax, Part II: Thoracic Cavity Figure 5.15 The interior of the bronchial tree as seen through an operating bronchoscope. A. The bifurcation of the trachea. Note the ridge of the carina in the center and the opening into the right main bronchus on the right, which is a more direct continuation of the trachea. B. The left main bronchus. The openings into the left upper lobe bronchus and its division and the left lower lobe bronchus are indicated. (Both images are courtesy of E. D. Andersen.) Blood Supply (Fig. 5.lSA; also see Fig. 5.lOB). The bronchi divide The inferior thyroid arteries (branches of the sub- dichotomously, eventually giving rise to several mil- clavian arteries) supply the upper two thirds of the lion terminal bronchioles that terminate in one or more trachea. and the bronchial arteries (branches of the respiratory bronchioles. Each respiratory bronchiole thoracic aorta) supply the lower third. dlvtdes into 2 to 11 alveolar ducts that enter the alveolar sacs. The alveoli arise from the walls of the sacs as dlver- tlcula (see Bronchopubnonary Segments, to follow). Lymph Drainage Each principal bronchus supplies an entire lung (see The lymph drains into the pretracheal and paratracheal Fig. S.12). The principal bronchi next divide Into lobar lymph nodes and the deep cervical nodes. (secondary) bronchi that supply the individual lobes of the lungs. The right principal (main) bronchus is wider. Nerve Supply shorter, and more vertical than the left and ls about The vagus and recurrent laryngeal nerves carry the 1-in. (2.5-