Practical Atlas of Computed Tomography Hariqbal Singh, Sushil Kachewar
INDEX
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Chapter Notes

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1Respiratory System
2
  • Normal Lung
  • Pulmonary Infections
  • Tumors of the Lung
  • The Pleura
  • Trauma
  • Miscellaneous Chest Conditions
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NORMAL LUNG1

 
1.1 CT Lungs
 
Normal Anatomy
Embryologically airway starts developing by fifth week of gestational age in the form of lung buds which grow from ventral aspect of primitive foregut. Trachea and esophagus are also separated by fifth week. Hereafter tracheobronchial tree is formed from fifth to fifteenth week. There are 23–25 airway generations from trachea to bronchiole. A bronchus has cartilage in the wall. Bronchiole is devoid of cartilage.
Interstitium of lung is divided into axial interstitium, parenchymal interstitium and peripheral interstitium. Axial interstitium is made of bronchovascular sheaths and lymphatics. Parenchymal interstitium includes interalveolar septum along alveolar walls. Peripheral interstitium includes sub pleural connective tissue and interlobular septa which encloses the pulmonary veins and lymphatics.
Pulmonary circulation includes primary pulmonary circulation, bronchial circulation and the anastomoses between the two. Primary pulmonary circulation consists of pulmonary arteries and veins that travel down to subsegmental bronchial level and has a diameter same as that of the accompanying airway. Main pulmonary artery arises from the right ventricle.
Bronchial circulation originates from thoracic aorta and supplies through the intercostal arteries which are two in number for each lung.
 
Segmental Division of Lungs
Right lung has following three lobes:
  1. Upper lobe which has an apical, anterior and a posterior segment.
  2. Middle lobe has a lateral and a medial segment.
  3. Lower lobe has superior segment, medial basal segment, anterior basal segment, lateral basal segment and a posterior basal segment.
Left lung has following two lobes:
  1. Upper lobe which has an apico-posterior, anterior, superior lingular and an inferior lingular segment.
  2. Lower lobe has superior segment, antero-medial basal segment, lateral basal segment and a posterior basal segment.
Left lung has no middle lobe.
 
Axial Sections of CT Chest (Figs 1.1A to 1.1L)
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Fig. 1.1A:
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Fig. 1.1B:
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Fig. 1.1C:
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Fig. 1.1D:
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Fig. 1.1E:
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Fig. 1.1F:
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Fig. 1.1G:
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Fig. 1.1H:
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Fig. 1.1I:
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Fig. 1.1J:
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Fig. 1.1K:
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Fig. 1.1L: Axial CT sections of chest