E Pleura and Lungs
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Bailey & Love · Essential Clinical Anatomy · Bailey & Love · Essential Clinical Anatomy Essential Clinical Anatomy · Bailey & Love · Essential Clinical Anatomy · Bailey & Love Bailey & Love · Essential Clinical Anatomy · Bailey & Love · EssentialChapter Clinical4 Anatomy e pleura and lungs • The pleura ............................................................................63 • MCQs .....................................................................................75 • The lungs .............................................................................64 • USMLE MCQs ....................................................................77 • Lymphatic drainage of the thorax ..............................70 • EMQs ......................................................................................77 • Autonomic nervous system ...........................................71 • Applied questions .............................................................78 THE PLEURA reections pass laterally behind the costal margin to reach the 8th rib in the midclavicular line and the 10th rib in the The pleura is a broelastic serous membrane lined by squa- midaxillary line, and along the 12th rib and the paravertebral mous epithelium forming a sac on each side of the chest. Each line (lying over the tips of the transverse processes, about 3 pleural sac is a closed cavity invaginated by a lung. Parietal cm from the midline). pleura lines the chest wall, and visceral (pulmonary) pleura Visceral pleura has no pain bres, but the parietal pleura covers the lungs. These two pleural layers are continuous is richly supplied by branches of the somatic intercostal and around the root of the lung and are separated by a thin lm phrenic nerves. Lymph from the pulmonary pleura passes to of serous uid, permitting them to glide easily on each other. a supercial plexus in the lung and then to the hilar nodes. The layers are prevented from separating by the uid’s sur- Parietal pleura drains to the parasternal, diaphragmatic and face tension and the negative pressure in the thoracic cavity. posterior mediastinal nodes. Thus, when the thoracic cage expands, the lung also must expand, and air is inhaled. Parietal pleura lines the ribs, costal cartilages, intercostal spaces, lateral surface of the mediastinum and upper surface 1&2 1&2 of the diaphragm. Superiorly, it extends above the thoracic inlet into the neck as the cervical dome of pleura; inferiorly, around the margin of the diaphragm, it forms a narrow gut- 6 ter, the costodiaphragmatic recess; anteriorly, the left costal and mediastinal surfaces are in contact, extending in front of the heart to form the costomediastinal recess. Mediasti- 1&2 nal pleura invests the main bronchi and pulmonary vessels 3 and passes on to the surface of the lung to become visceral pleura, which covers the lung and extends into its interlobar 4 8a ssures. The surface markings of the pleural sacs should be noted 5 8b 5 (Figs 4.1 and 4.2). On both sides, the upper limit lies about 2 3 cm above the medial third of the clavicle. From here, the lines of pleural reections descend behind the sternoclavic- 1 ular joints to almost meet in the midline at the level of the 7 2nd costal cartilage. At the 4th costal cartilage, whereas the left pleura deviates laterally and descends along the lateral Figure 4.1 Surface markings of the pleura and lungs, anterior aspect: 1, pleural markings; 2, lung markings; 3, cardiac border of the sternum to the 6th costal cartilage, the right notch; 4, horizontal ssure; 5, oblique ssure; 6, trachea; pleural reection continues down, near to the midline, to the 7, costodiaphragmatic recess; 8, diaphragm, (a) inspiration, 6th costal cartilage. At this point, on both sides, the pleural (b) expiration 04_K35605_IllusClinical_2e_Ch4.indd 63 09/07/2018 16:28 PART 1 | THE THORAX 64 CHAPTER 4 The pleura and lungs 1&2 3 1&2 1&2 4a 2 4b 1 (a) Figure 4.2 Surface markings of the pleura and lungs, posterior aspect: 1, pleural markings; 2, lung markings; 3, oblique ssure; 4, diaphragm, (a) inspiration, (b) expiration. The black dotted line shows the incision for opening the chest through 5th intercostal space The pleural sac is a potential space that can in patho- logical conditions ll with uid or air; with blood after intrathoracic haemorrhage (haemothorax); with inam- matory exudate (pleural effusion) or pus (pyothorax) (Fig. 4.3); or with air (pneumothorax) (Fig. 1.6, p. 00) after chest wall trauma that has torn the lung or after the rupture of a lung bulla that has burst the visceral pleura. A distended pleural cavity may interfere with lung expansion. Fluid may be drained from the pleural cavity by insertion of a needle or tube, attached to an underwater seal, into the 7th intercos- (b) tal space in the midaxillary line (Figs 1.7a and 1.9, p. 00). Figure 4.3 (a) Left pleural effusion obliterating much of the lower Insertion below this level runs the risk of the needle pene- lung markings; (b) localized interlobar uid collection (arrow) trating the diaphragm and the underlying liver or spleen. To avoid danger to the neurovascular bundle, it is best to insert the needle along the top of the rib, which avoids the vessels lying in the subcostal groove. Emergency aspiration of air is most safely achieved by inserting a needle, attached to an underwater seal or utter valve, into the 2nd or 3rd THE LUNGS intercostal space in the midclavicular line. These paired organs lie in separate pleural sacs attached to Punch biopsy needles inserted through the intercostal the mediastinum at the hila (Figs 4.1, and Figs 4.6 and 4.7 space allow specimens of pleura to be obtained for histological below). Spongy and elastic in composition, they conform to examination. Pleurisy – inammation of the pleura – causes the contours of the thoracic cavity. The right lung weighs pain that is magnied by respiratory movements. The pain about 620 g, and the left about 560 g. They have a charac- is referred by sensory bres within the parietal pleura to the teristic mottled appearance on radiographs – lung tissue is cutaneous distribution of the nerve supplying it. Thus costal clear; denser shadows at the hilus are caused by hilar lymph inammation is referred to the chest wall or, in the case of nodes, and radiating shadows by blood vessels. A posteroan- lower nerves, to the upper abdominal wall, and inammation terior (PA) chest X-ray will also reveal the normal aortic arch of the diaphragmatic pleura is referred to the area supplied by (knuckle), the inferior vena cava and the outline of the heart. the nerve root (C4) from which originates the phrenic nerve, A lateral view reveals details of the mediastinal structures i.e. to the tip of the shoulder. (Figs 4.4 and 4.5). 04_K35605_IllusClinical_2e_Ch4.indd 64 09/07/2018 16:28 PART 1 | THE THORAX The lungs 65 Figure 4.5 Lateral chest X-ray showing mediastinal structures: 1, manubriosternal joint; 2, sternum; 3, cardiac shadow; 4, trachea; 5, border of scapula; 6, vertebral bodies; 7, retrocardiac space; 8, domes of diaphragm Figure 4.4 Radiograph of the chest: 1, trachea; 2, aortic knuckle; 3, 1st costochondral junction; 4, hilar shadows; 5, left ventricle; 6, left costodiaphragmatic recess; 7, right dome of diaphragm; 8, inferior vena cava; 9, right atrium Upper lobe Groove for left subclavian artery Left pulmonary artery Groove for left common carotid artery Upper lobe Left main bronchus Groove for aortic arch Oblique Pulmonary veins ssure Cardiac impression Groove for descending Oblique ssure Lingula thoracic aorta Pulmonary ligament Cardiac notch Cardiac notch Lingula Lower lobe Lower lobe Inferior surface (a) (b) Inferior border Figure 4.6 Left lung: (a) lateral surface; (b) medial surface Each lung has an apex in the root of the neck, and a base into an upper and lower lobe (Fig. 4.6); oblique and hori- resting on the diaphragm. The base is separated by a sharp zontal ssures divide the right lung into upper, middle and inferior border from a lateral convex costal surface and a lower lobes (Fig. 4.7). The oblique ssure on each side can be medial concave mediastinal surface, in the centre of which marked by a line around the chest wall from the spine of the are the structures of the lung root surrounded by a cuff of 3rd thoracic vertebra to the 6th costochondral junction. The pleura (Figs 4.6 and 4.7). The deeper concavity of the left horizontal ssure is marked by a horizontal line passing from lung accommodates the heart’s left ventricle. The left lung’s the 4th right costal cartilage to the oblique line previously anterior border is deeply indented by the heart to form the drawn (Figs 4.1 and 4.2). The lower lobes of both lungs lie cardiac notch; the rounded posterior border of each lung lies below and behind the oblique ssure and comprise most of in the paravertebral sulcus. the posterior and inferior borders. The upper lobe of the left The lungs are each divided by ssures extending deeply lung is above and anterior to the oblique ssure, and includes into their substance. An oblique ssure divides the left lung the apex and most of the mediastinal and costal surfaces. The 04_K35605_IllusClinical_2e_Ch4.indd 65 09/07/2018 16:28 PART 1 | THE THORAX 66 CHAPTER 4 The pleura and lungs Groove for Apex the superior Groove for right vena cava subclavian artery Upper lobe Division of Impression of right pulmonary azygos vein artery Oblique ssure Oblique Division of right ssure main bronchus Groove for oesophagus Horizontal Anterior border of ssure Pulmonary veins heart Lower lobe Pulmonary Middle lobe Horizontal ligament ssure Groove for inferior vena cava (a) (b) Base of lung Figure 4.7 Right lung: (a) lateral surface; (b) medial surface Right Left Apical (UAP) Posterior (UP) Apico - posterior (UAP) Anterior (UA) Anterior (UA) Superior (SL) Lingular Lateral (LM) Apical basal Inferior (IL) Middle lobe Medial (MM) (LAP) Anterior basal (LA) Medial basal Anterior basal (LA) (LM) Lateral basal (LL) Lateral basal (LL) Posterior basal (a) (LP) Left lung L medial L lateral Right lung R Medial R Lateral UAP UAP UAP UAP UA UP UP UP LAP UA UA LAP UA LAP SL LAP IL SL LP LM MM ML MM IL LP LP LL LA LA LA LM LL LL (b) (c) Figure 4.8 (a) Bronchial tree.