Handbook on Clinical Approach to Respiratory Medicine K Surendra Menon, R Pajanivel
Page numbers followed by f refer to figure and t refer to table.
Abdomen, acute 15
Accessory muscles 12
Acid-fast bacilli 82
staining 82
Acquired immunodeficiency syndrome 42
Adenopathy 113f
Admission, criteria for 125
Aegophony sign 79
Allergic disorders 32
Allergy 18
testing 83
American Thoracic Society 74
Amphoric breathing 72
Anatomic shunts 39
Anatomical principles 1
Angina 29
Angiotensin-converting enzyme 21, 33
Angle of Louis 1, 2
Anthropometry 37
Antinuclear antibody 85
Aortic arch 110
Aortic knuckle 110
Aortopulmonary window 110
Apical impulse 54
position of 52
Apical region 55
Apneustic breathing 52
Appetite, loss of 31
Arterial blood gas 126
Arterial oxygen saturation, decreased 39
Asbestos bodies 82
Aspergilloma 24
Aspiration pneumonia 32, 33
Asthma 32
acute severe 124
history of 34
life-threatening 124
moderate exacerbation of 123
near-fatal 124
severe 126
Ataxic breathing 52
Auscultation, principles of 71
Axillary area 4
Axillary line, posterior 7
Bacteroides 24
Barrel chest 48
Bell tympany 80
Bilateral coarse miliary shadows 118f
Bilateral cystic lesions 120f
Biot's breathing 52
gases 126
pressure 38
routine 81
tests 89
Bony cage 100
Bony landmarks 104f
Branding scars 38
implant 103f
tissue, absence of 101f
Breath sound, normal 72, 73f
disorders, sleep-related 84
tubular 71, 72
types of 51
Breathlessness 18, 26
severe 125
Bronchial arterial embolization 135
Bronchial asthma 82, 84
acute exacerbation of 123
Bronchial breath 72
sounds 72, 73f
Bronchiectasis 44, 120f
Bronchophony 79
Bronchopulmonary segments 11, 11t
Budesonide 130
Bulbar conjunctiva 39
Bullous emphysema 78
Carboxyhemoglobinemia 40
Carcinoembryonic antigen 85t
Cardiac dullness 69
Cardiophrenic angles 111f
Cardiothoracic ratio, causes of increased 111
Cardiothoracic surgery 81
Cardiovascular system 44
Cavernous breathing 72
Cellulitis 29
Central cyanosis 39, 40
causes 39
Central pneumonia 80
Central tendon 14
Certain important tests 84t
Cervical rib, left 105f
expansion, measurement of 57, 57f
pain 18, 29
shape of 47
size of 47
topography 3, 4f, 6f
type of 47
Chest wall
anterior 6f, 60f
expansion 56f
lateral 7f
posterior 6f, 60f
right 102f
subcutaneous calcifications, left 102f
symmetry 48
Chest X-ray 100f102f, 105f, 106f, 111f113f, 115f120f, 126
cardiac size in 110f
interpretation 121
lateral view 93f
mediastinal compartments in 107f
normal 104f
over penetrated 98f
reading of 89, 98
standard posteroanterior view 92f
systematic reading of 96, 97
underpenetrated 99f
Cheyne–Stokes breathing 52
Chronic obstructive pulmonary disease, acute exacerbation of 130
Clavicular fracture 104
Clavicular percussion 65
Clubbing 38
causes of 44
differential 45
unidigital 45
Cobbler's chest 48
Coin test 80
Common respiratory symptoms 18, 19
Compensatory emphysema 66
Constitutional symptoms 18, 30
Costal angle 16
Costochondritis 29
Costophrenic angles 111f
Cough 18, 19
barking 20
bovine 20
brassy 20
causes of 21t
characteristics of 21t
dry 20
paroxysmal 20
types of 20
with expectoration 22
COVID-19, tests for 82
Cracked pot resonance 67
Crackles 75
midinspiratory 76
production of 75
Cricoid cartilage 1
Crura tendon 14
Curschmann's spirals 82
Cyanosis 38, 39
Cystic fibrosis 84
Cystic lesion, well-defined 119f
Cysts and cavities 115
D'espine sign 80
Dark lung fields 98f
history of 34
mellitus 32
Diagnose tension pneumothorax 133
Diagnostic skin tests 89
Diaphragm 13, 13f, 111
Differential cyanosis 40
causes 40
Direct percussion 65
Distal phalangeal depth 43, 44f
Dysphagia 18, 30
Dyspnea 18, 2628
chronic 27
grading of 27
on exertion 28
subacute 27
Ear, nose, and throat 81
Early inspiratory crackles 76
Ectopic endometrial tissue 33
Emphysema 48, 66, 120f
Empyema 44
Endemic hemoptysis 26
Eosinophils 81
Epilepsy, history of 34
Erythrocyte sedimentation rate 81
Expiration, muscles of 12
Fever 30
types of 31
Fissure, horizontal 114
Fluticasone 130
Forced expiratory volume 123, 125
Formoterol 130
Foul-smelling sputum 24
Fusobacterium 24
Garland's triangle 70
Gastroesophageal reflux disease 21, 29
Gastrointestinal system 45
Grocco's triangle 70
Hacking dry cough 20
Hamman sign 78
Headache 18
Heart 108
Heart border
percussion of
left 69
right 69
right 108
Hematemesis 26t
Hemoglobin 39
abnormality 40
Hemoptysis 18, 24, 25, 26t, 134
assessment 135
management of 135
minimal 25
moderate 25
position 135
Hepatopulmonary syndrome 28
Herpes 29
Hilar enlargement, bilateral 113f
Hilum 17, 111
Hoover's sign 52
Human immunodeficiency virus 81, 118f
Hypertension 32
history of 34
treatment for 33
Hypertrophic pulmonary osteoarthropathy 43
Icterus 38, 39
Idiopathic pulmonary arterial hypertension 19
Immunological tests 84
Implantable cardioverter defibrillator 38
Infra-axillary area 4
Inspiration 58
Intensive care unit 91
Intercostal neuralgia 29
Interferon-gamma release assays 85
Interphalangeal depth 43, 44f
Interscapular area 4
Interstitial lung disease 21, 116f
Interstitial reticular densities, bilateral diffuse 116f
Ipratropium bromide 127, 130
combination of 130
Jugular venous pulse 38, 46
causes of increased 46
Kronig's isthmus 8, 66
Kussmaul breathing 52
Kyphosis 50f
Larynx, lower border of 1
Late inspiratory crackles 76
Left costophrenic angle 112f
Left upper lobe 9
bronchus 11
Light-emitting diode 82
Lingula 11
Liquid bridge hypothesis 76
dullness 69
function testing 83
surface anatomy of 8
upper 9, 10
Lordotic view 93
Lovibond's angle 42, 42f
Lower lobe
left 9, 10
pneumonia 115f
right 9, 10, 115f
Lower respiratory tract 47, 85
abscess 21, 44
carcinoma 117f
diseases, radiological patterns of 114, 115t
fields 114
left 8, 10f
lobes 9f, 10f
malignancy of 41
markings, prominence of 99f
secondaries 116f
surface anatomy of 8
tissue, wedge of 11
volumes 115, 120f
Lymphadenopathy 38, 41
Lymphangioleiomyomatosis 19
Lymphocytes 81
Lymphomas 42
Marfan syndrome 48
Massive hemoptysis 25
Mastectomy, right 101f
Mastitis 29
Mediastinal crunch 78
Mediastinitis 29
Mediastinum 14, 15f, 104, 107
inferior 14, 108
lower 108
superior 107
upper 107
Menorrhagia 39
Metallic cough 20
Methemoglobinemia 40
Midaxillary line 7
Middle and lower regions 55
Monophonic wheeze 74
Muscular fibers 13
Myalgia 29
Myocardial infarction 29
Myotatic irritability 66
Nebulizer solutions available 130
Nodular densities, bilateral 116f
N-terminal pro-brain natriuretic peptide 85
Obstructive airway diseases 12
Obstructive pulmonary disease, chronic 19, 39
Oral cavity 47
Orthodeoxia 28
Orthopnea 28
Ortner's syndrome 29
Over penetrated film 97
Oxygen 126
saturation 125
Pallor 38
Palpation 53, 85
Parasitic infestation 101f
Paratracheal stripes 106f
Parietal pleura 15
Paroxysmal nocturnal dyspnea 28
Patent ductus arteriosus 40
Peak expiratory flow 125
Pectus carinatum 48, 49f
Pectus excavatum 48f
Pedal edema 38, 45
Pedigree chart 32f
Peptostreptococcus 24
Percussion 61
anterior 62, 62f
cardinal rules of 63
lateral 63
note, types of 66
posterior 63, 63f
Peripheral cyanosis 40, 41
causes 40
Pigeon chest 48
Platypnea 28
Pleura 15
sac 15
Pleural diseases 115
Pleural effusion 71, 112f
right 94f, 121f
Pleural rub 77
Pleuritic pain 29
Pleurodesis 134
Pleximeter finger 64
middle phalanx of 64f
Plexor finger 64f
Pneumomediastinum 78, 134
Pneumonia 21
Pneumothorax 66, 71
left-sided 78
small 93
Polymerase chain reaction 82
Polyphonic wheeze 75
Positive end-expiratory pressure 129
Post-tussive suction 79
Premenstrual pain 29
Primary ciliary dyskinetic syndromes 84
Principal muscles 12
Profile sign 44
Pseudoclubbing 45
Pseudohemoptysis 26
Pseudomonas infections 23
Pulled trachea syndrome 73
Pulmonary artery, left 110
Pulmonary edema 21
Pulmonary emergencies, management of 123
Pulmonary function testing 83
Pulmonary squeak 76
Pulmonary tuberculosis 85, 119f
Pulse 37
oximetry 38, 125
Pursed lip breathing 52
Pyopneumothorax 68
Radial pulse
left 38
right 38
Rapid shallow breathing 52
Rectus abdominis 12
Renal function testing 83
abnormalities in 51
muscles of 11
types of muscles of 11
Respiratory diseases, symptoms of 19
Respiratory evaluation, common investigations in 81
Respiratory failure 136138
classification 136
Respiratory illness, history of 134
Respiratory movements 55
Respiratory rate 38
Respiratory system 44
anatomy of 1
diseases of 17
examination of 37, 47
Retrosternal thyroid 20
Rhonchi 74
Rib 3
cage 12
erosions 29
fracture of 29, 104
fusion of 105f
Rifampicin 33
Right clavicle, bony mass in 106f
Right lateral decubitus film 94f
Right lung 8, 10f
mass lesion 117f
Right middle lobe 9, 10, 115f
bronchus 11
Right upper lobe 9, 10, 96f
bronchiectasis 17
bronchus 11
Roentgenography 89
Rule out artifacts 96
Salbutamol 130
Scalene muscles 12
Scapula, spine of 4
Scapular line 7
Schamroth's sign 43, 43f
Scoliosis 51f
Scratch sign 80
Serratia marcescens 26
angiotensin-converting enzyme 85
bilirubin 39
Shifting dullness 68
percussion for 68
Shock 134
Shoulder, drooping of 50f
Skodaic resonance 67
disordered breathing 52
disturbances 18, 30
Smoking index 32
Sneezing, rhinitis 18
Soft tissue 100
bilateral 100f
calcifications 101f
density 103f
Solitary pulmonary nodule 89
added 74
adventitious 74
Spinal abnormalities 49
Spinous process 16
Splenic dullness 70
Spurious hemoptysis 25
Sputum collection 82
Sputum malignant cytology 82
Squamous cell carcinoma 85
Sternal percussion 65
Sternocleidomastoid sign 52, 53f
Steroid therapy 127
Stony dull 67
Straight line dullness 68
Stress relaxation quadrupole hypothesis 75
Stridor 18, 30, 52
Succussion splash 78
Suprascapular area 4
Symptomatology 17
Tactile vocal fremitus 61
Tension pneumothorax 132
causes 132
examination 133
possible complications 134
prognosis 134
symptoms 133
treatment 133
Thoracic cavity 12, 13
Thoracic movements 52
Thoracic vertebra 114
Tidal percussion 68
Tietze syndrome 29
Trachea 1, 104
palpation of 54f
Tracheal descent 58
Tracheal tug 58
Trail's sign 52, 53f
Transversus abdominis 12
Trapped air increases, amount of 132
Traube's space 3, 70
Trepopnea 28
Tuberculous lymphadenopathy 41
Upper airway cough syndrome 24
Upper respiratory tract 1, 47, 85
Vena cava, superior 3
Ventilatory respiratory failure 137
Ventilatory support 129
Vertebral line 7
Vesicular breath sound 72
Virchow's node 42
Vital signs 37
Vocal fremitus 58, 60f
examination 61f
Vocal resonance 77
Voice, hoarseness of 18, 29
Weight loss 31
significant 31
Wheeze 18, 30, 74
mechanisms of 74
Whispering pectoriloquy 79
Xiphisternum 14, 16
Chapter Notes

Save Clear

Anatomical PrinciplesCHAPTER 1

One should have a clear understanding of anatomy of the respiratory system to perform a proper physical examination. Some of the important anatomical landmarks are outlined below.
The upper respiratory tract starts from the mouth or nose and includes all the structures in the mouth, nose, and sinus up to the larynx (the details of which will be discussed later). Lower respiratory tract starts from the lower border of cricoid cartilage which includes the trachea, airways, and lung parenchyma containing alveoli.
  • Starts from cricoid cartilage (lower border of larynx at the level of 6th cervical vertebra posteriorly) to sternal angle anteriorly (angle of Louis) and T5 spinous process posteriorly, where it divides into left and right main stem bronchi. The inner diameter is 25 mm and the length is about 10–16 cm.
  • Trachea is generally in the midline, but slight deviation to right may occur in normal individuals (by right aortic arch and weight of right lung). The weight of right adult lung ranges from 375 to 550 g and the left lung ranges from 325 to 450 g.2
  • Trachea has intra- and extrathoracic components. This has important bearing in the understanding of physiology of variable obstruction.
The spinous process is an important landmark because of its prominence and thoracic spines can be counted below it.
Angle of Louis
  • Angle of Louis is the angle between the body of sternum and manubrium. Many important landmarks occur at this level:
    • 2nd rib articulates with manubrium sterni at this site. The ribs are counted anteriorly starting from this point.
    • Carina of trachea is at this level and it branches into right and left bronchi.
    • Mediastinum is divided into superior and inferior at this level.
With the help of surface anatomy, the thorax is arbitrarily divided into various spaces and lines. Description of abnormal signs in relation to the ribs, intercostal spaces (areas), and lines help to localize the lesion anatomically (upper lobe, lower lobe, middle lobe, etc.).
It is a significant anatomical landmarks as:
  • Ribs are counted from this level to downward. 2nd rib lies at sternal angle.
  • It marks the plane of separation of superior and inferior mediastinum.
  • Ascending aorta ends, arch of aorta starts and ends, and descending aorta begins at this level.
  • Trachea divides into two principle bronchi (right and left).3
  • Azygos vein arches over the roof of the right lung and opens in superior vena cava (SVC).
  • Pulmonary trunk divides into two pulmonary arteries below this level.
  • Thoracic duct crosses from right to left side and reaches left side at the level of sternal angle.
  • It marks the upper limit of the base of the heart.
  • Cardiac plexus are situated at the same level.
Anteriorly ribs are counted down starting from 2nd rib. There are 12 ribs and 11 interspaces in each hemithorax. You can also count up from 12th rib. Inferior angle of scapula overlies 7th thoracic rib posteriorly.
Spaces/Areas (Chest Topography)
Anteriorly, the spaces are supraclavicular, infraclavicular and mammary, and Traube's space (Fig. 1).
  • Supraclavicular: Space above clavicle.
  • Infraclavicular: Space below clavicle up to 2nd intercostal space.
  • Mammary: Space below infraclavicular area, i.e., 2nd to 6th intercostal space
  • Traube's (semilunar) space: It is a crescent-shaped space, encompassed by the lower border of the left lung, the anterior border of the spleen, the left costal margin, and the inferior margin of the left lobe of the liver. Thus, its surface markings are respectively the left 6th rib superiorly, the left anterior axillary line laterally, and the left costal margin inferiorly. In other words, left 6th rib in the midclavicular line to 8th costal cartilage in the parasternal line, then along the left costal margin to the 11th rib in the midaxillary line and then the 9th rib in midaxillary line.4
zoom view
FIG. 1: Chest topography—space/area.
Laterally, the spaces are axillary and infra-axillary spaces bound in between by two axillary folds. Anterior axillary fold is formed by pectoralis major muscle and posterior axillary fold by latissimus dorsi and teres major muscles.
  • Axillary area: Space up to 5th intercostal space in midaxillary line (on the right where the horizontal fissure meets the oblique fissure).
  • Infra-axillary area: Below the 5th intercostal space to 7th intercostal space.
Posteriorly, the spaces are suprascapular, interscapular, and infrascapular spaces (Fig. 2).
  • Suprascapular area: From the apex to the spine of scapula.
  • Interscapular area: From the spine of scapula to the angle of scapula.5
  • Infrascapular area: From the angle of scapula to the 11th rib.
zoom view
FIG. 2: Posterior spaces.
Following are the imaginary vertical lines in the chest: Midsternal, parasternal, midclavicular, anterior axillary, midaxillary, posterior axillary, infrascapular, and vertebral lines (Figs. 3 to 5).
  • Midsternal line: A vertical line down the middle of sternum.
  • Parasternal line: A vertical line along lateral edges of sternum.
  • Midclavicular line: A vertical line from midpoint of clavicle.
  • Anterior axillary line: A vertical line along anterior axillary fold.6
    zoom view
    FIG. 3: Chest topography—important lines on anterior chest wall.
    zoom view
    FIG. 4: Important lines on posterior chest wall.
    zoom view
    FIG. 5: Important lines on lateral chest wall.
  • Midaxillary line: A vertical line at midpoint between anterior and posterior axillary line. There is less muscle attachment here, so it is the ideal place for putting intercostal drain and for thoracoscopy incision. This is also called safe triangle because there is less risk of injuring blood vessels like internal mammary artery and damage to muscle and breast tissue.
    • Safe triangle: It is bordered by the anterior border of the latissimus dorsi, the lateral border of the pectoralis major muscle, inferiorly by horizontal line from the nipple (5th intercostals space) just above the rib (to avoid neurovascular bundle) and superiorly by the axilla.
  • Posterior axillary line: Along posterior axillary fold.
  • Scapular line: Starting from the suprascapular area passing down the inferior angle of scapula.
  • Vertebral line: Over spinous processes in the midline.8
Surface Anatomy of Lungs
Right Lung
With a marking pen, start 3 cm above clavicle in midclavicular line, come down along right parasternal line, to join 6th rib in midclavicular line, to 8th rib in midaxillary line and to 10th rib posteriorly. Posterior marking of lung is from the apex to 10th thoracic vertebra posteriorly.
Left Lung
Start 3 cm above clavicle in midclavicular line and draw a line going downward along the parasternal margin up to 4th costal cartilage. Between 4th and 6th costal cartilage, deviate to left by 4 cm. The lower levels of lung—6th rib in the midclavicular line, 8th rib in the midaxillary line, and 10th rib in the scapular line.
Kronig's Isthmus
It is an area about 5–7 cm in the supraclavicular region. It is bound medially by scalenus muscle, laterally by acromion process of scapula, anteriorly by clavicle, and posteriorly by trapezius muscle.
Clinical Significance
Normal percussion over Kronig's isthmus is resonant. The percussion note becomes hyperresonant in emphysema and impaired in early tuberculosis and apical lung tumors.
Surface Anatomy of Lobes (Figs. 6 to 8)
Oblique fissure extends on the left from the tip of spinous process of the T3 vertebra that extends down to the level of 6th costochondral junction anteriorly. In taking this route, the approximate path of the 6th rib is followed. The posterior origin of the fissure on the right is slightly inferior—the inferior margin of the T4 vertebra. If the subject keeps his hands on the head, the line drawn from the spinous process of the above vertebrae T4 on the right and T3 on the left along the lower border of the scapula to the level of 6th costochondral junction.9
zoom view
FIG. 6: Anterior surface markings of the lung lobes.(LLL: left lower lobe; LUL: left upper lobe; RLL: right lower lobe; RML: right middle lobe; RUL: right upper lobe)
zoom view
FIG. 7: Posterior surface markings of the lung lobes.(LLL: left lower lobe; LUL: left upper lobe; RLL: right lower lobe; RUL: right upper lobe)
zoom view
FIGS. 8A AND B: Lateral surface markings of the lung lobes. (A) Right lung; and (B) Left lung.(LLL: left lower lobe; LUL: left upper lobe; RLL: right lower lobe; RML: right middle lobe; RUL: right upper lobe)
Transverse fissure starts from the level of the right 4th costal cartilage horizontally to a junction with the oblique fissure at approximately the midaxillary line in the 5th intercostal space.
Remember there are three lobes on the right side and two lobes on the left side normally.
Once the fissures are drawn, one can easily recognize the surface anatomy of lobes of lungs. One can then appreciate the importance of examining the patient in all anatomical areas mentioned above to identify the lobes. Most of the lower lobe is in back, the upper lobe is in front, and the middle lobe is in front and in the axilla all the three (right) lobes are present.11
Bronchopulmonary Segments
It is a wedge of lung tissue supplied by a single bronchus and corresponding pulmonary artery and vein. There are ten segments in right lung and eight segments in left lung (Table 1).
Muscles of Respiration
There are two types of muscles of respiration—principal and accessory muscles.
TABLE 1   Bronchopulmonary segments.
Right lung
Left lung
Right upper lobe bronchus
Left upper lobe bronchus
  • Apical segment (1)
  • Apicoposterior segment (1 and 2)
  • Posterior segment (2)
  • Anterior segment (3)
  • Anterior segment (3)
Right middle lobe bronchus
  • Lateral segment (4)
  • Superior segment (4)
  • Medial segment (5)
  • Inferior segment (5)
  • Apical (superior) segment (6)
  • Apical (6)
  • Medial basal segment (7)
  • Anterior basal segment (8)
  • Anterior basal segment (8)
  • Lateral basal segment (9)
  • Lateral basal (9)
  • Posterior basal segment (10)
  • Posterior basal (10)
Note: No medial basal segment in left lung.12
Principal muscles are used during normal inspiration while accessory muscles are used during forced breathing (heavy exercise and exacerbations of obstructive airway diseases).
Principal muscles include external intercostals, interchondral part of internal intercostals, and diaphragm.
The width of the thoracic cavity (lateral and anteroposterior diameter) is increased by external and interchondral part of internal intercostals which elevate the ribs. The lateral dimensions of the thorax are increased by the bucket handle movement of the ribs. Diaphragm contracts to increase the vertical dimensions of thoracic cavity and also aids in elevation of lower ribs and abdominal contents are pushed downward. Accessory muscles of inspiration are sternocleidomastoid which elevates the sternum and scalene muscles (anterior, middle, and posterior) elevate the first two ribs.
Remember to look for alae nasi when the patient is in respiratory distress that means a fall in forced expiratory volume in the first second (FEV1) by 30%.
Muscles of expiration: It is passive as no muscle involvement in normal breathing. The process is simply done by elastic recoil of the lungs and the rib cage.
But during active breathing (exercise), the interchondral part of the internal intercostal muscles assists in active expiration by pulling the ribs downward and inward. They also prevent bulging of intercostal spaces during straining such as vigorous coughing and vomiting. The abdominal muscles when contract (rectus abdominis, external oblique, internal oblique, and transversus abdominis), intra-abdominal pressure increases and push the diaphragm upward and force the air out of the lungs.13
Diaphragm (Fig. 9)
The diaphragm is a dome-shaped structure containing muscle and fibrous tissue that separates the thoracic cavity from the abdomen. The dome curves upward. The superior surface of the dome forms the floor of the thoracic cavity and the inferior surface of the dome forms the roof of the abdominal cavity.
As a dome, the diaphragm has peripheral attachments to structures that make up the abdominal and chest walls. The muscle fibers from these attachments converge in a central tendon, which forms the crest of the dome. Its peripheral part consists of muscular fibers that take origin from the circumference of the inferior thoracic aperture and converge to be inserted into a central tendon.
The muscle fibers of the diaphragm emerge from many surrounding structures. Anteriorly, fibers emerge from behind the xiphoid process and the cartilages of the floating ribs (ribs 7–12). Laterally, fibers emerge from the sides of the ribs themselves, including the two false ribs 11 and 12. Posteriorly, fibers emerge from the abdominal wall and lumbar vertebrae. There are two lumbocostal arches, medially and laterally.
zoom view
FIG. 9: Diaphragm.
Crura and central tendon: The left and right crura are tendinous in structure and blend with the anterior longitudinal ligament of the vertebral column.
The central tendon of the diaphragm is a thin but strong aponeurosis situated near the center of the vault formed by the muscle, but somewhat closer to the front than to the back of the thorax, so that the posterior muscular fibers are the longer. Once the diaphragm has been outlined, you can appreciate that the pleural gutter is deep posteriorly. Fluid, thus, tends to accumulate posteriorly.
Mediastinum (Fig. 10)
Mediastinum is the space between the lungs from inlet to outlet of thorax. Superiorly, by suprasternal notch. Anteriorly, it is in between parasternal lines. Posteriorly, by vertebral line. Inferiorly, it extends to xiphisternum. Mediastinum is narrow posteriorly and widens anteriorly. Since the inlet of thorax is slanted, only posterior mediastinum extends to neck.
Sternal angle separates superior from inferior mediastinum. The inferior mediastinum is divided into anterior, middle, and posterior compartments. The space in front of the heart is anterior mediastinum and behind is posterior mediastinum. Heart itself defines the middle mediastinum. The posterior mediastinum is divided into two, i.e., paravertebral and prevertebral space. Superior mediastinum extends into the neck and is called cervicomediastinal space.
It is important to know the structures in each compartment. It is important to differentiate the masses in the mediastinum in relation to the structures there.15
zoom view
FIG. 10: Mediastinum.
Pleura and Pleural Sacs
Parietal and visceral pleura covers the surface of the lung. Parietal pleura lines inner surface of rib cage and outer portion of each hemidiaphragm is supplied by intercostal nerves and this is one reason for localized chest pain.
The pleura in the central region of each hemidiaphragm is innervated by fibers that travel with the phrenic nerve (C3–C4). So, in infection involving this area, the pain extends to ipsilateral neck or shoulder even to the abdomen presenting as acute abdomen. Parietal pleura has innervations and is pain sensitive but not the visceral pleura.
The pleural sac extends to 8th, 10th, and 12th rib in the midclavicular line, the midaxillary line, and scapular line, respectively at the lower level. There is a difference in the pleural reflection on the left side because the lung and the pleura from midsternal line lie at a higher level, i.e., at the lower border of the 4th costal cartilage. The superficial cardiac dullness is obtained in this area because the heart is uncovered.16
Hilum lies opposite to the spines of 4th, 5th, and 6th thoracic vertebrae. Left hilum is at a higher level.
Costal Angle
Costal angle (subcostal angle) is formed by the 10th rib with costal cartilage on both sides and xiphisternum in the middle. The normal angle is not >90° but more acute in males. Both the sides are symmetrical. Volume changes in each hemithorax will alter this relationship. Hyperinflated lungs will increase the costal angle. In alar chest, anterior–posterior distance is reduced. Diaphragmatic paralysis also alters the symmetry of costal angle.
Spinous Process
The most prominent spinous process is of 7th cervical vertebra. You can count down the thoracic vertebra and the ribs using this landmark.
To conclude, this chapter will throw light on the essentials of anatomy of thorax which will help in locating anatomical lesions with precession.