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• Lungs


  • Pair of respiratory organs situated in thoracic cavity
  • Right lung is larger than the left
  • Right lung has 3 lobes
  • Left lung has 2 lobes

  
• Main Fissures of Right Lung


  • Horizontal fissure
  • Oblique fissure

  
• Main Fissures of Left Lung

  • Oblique fissure

  
• Oblique (Major) Fissure


  • Right oblique fissure separates the lower lobe from the middle and upper lobes whereas left oblique fissure separates lower lobe from upper lobe
  • Extends from T4/T5 posteriorly to the diaphragm anteroinferior
  • The left oblique fissure is more vertically oriented than the right
  • Usually visible on a lateral radiograph and on a high-resolution CT scan as a curvilinear band from the lateral
• Accessory Fissures


  • Azygous fissure
  • Superior Accessory fissure
  • Inferior Accessory fissure
  • Left transverse Fissure

  
• Horizontal (Minor) Fissure


  • Separates upper lobe from the middle lobe of the right lung
  • Is short as compared to oblique fissure
  • The posterior limit is the right oblique fissure which it meets at the level of 6th rib
  • Anatomically complete on in 1/3rd of the subjects
• Accessory fissures of the lung


  • Azygous fissure
  • Inferior accessory fissure
  • Superior accessory fissure
  • Left minor fissure

  
• Azygous fissure


  • On the right side
  • Occurs due to anomalous development of azygous vein and terminates in tear drop opacity
• Superior Accessory Fissure


  • Separates the apical from the basal segments of the lower lobe
  • It is commoner on right side
  • It is seen in 5% of the PA chest radiograph
• Inferior Accessory Fissure


  • It seperates the medial basal broncho pulmonary segment from the rest of the lower lobe
  • Common on the right than left
  • It is seen in 8% of PA chest radiographs

  
• Lung Zones


  • Upper zone : upto 2nd rib
  • Middle zone: 2nd to 4th rib
  • Lower zone: 4th and below
• Lobes of Right Lung


  • upper lobe
  • middle lobe
  • lower lobe
• Lobes of Left Lung


  • upper lobe
  • lower lobe
• Pleura


  • Delicate serous membrane, which forms a closed invaginated sac enclosing the lungs and lines the thoracic cavity
  • Visceral pleura covers the surface of the lung and dips into the fissures between its lobes
  • Parietal pleura lines the non-pulmonary surface and named according to the site it lines: costal pleura, diaphragmatic pleura, mediastinal pleura, Apical pleura

  
• Mediastinum


  • Group of non-delineated organs and their surrounding connective tissue
  • Lies in the midline of the chest between the pleural surfaces of each lung and extends from the sternum to the vertebral column
  • Anatomic Relations: Superiorly – Thoracic outlet and the root of the neck, Inferiorly – Diaphragm, Anteriorly - chest wall, Laterally - lungs and pleura, posteriorly - Thoracic spine

  
• Radiological divisions of Mediastinum


  • Anterior
  • Middle
  • Posterior
• Contents of Superior Mediastinum


  • Aortic arch and branches
  • brachiocephalic veins and superior vena cava
  • Trachea
  • Esophagus
  • Thoracic duct
  • Lymph nodes
  • Nerves
• Contents of Anterior Mediastinum


  • Thymus
  • Mammary vessels
  • Lymph nodes

  
• Contents of Posterior Mediastinum


  • Descending aorta
  • Oesophagus
  • Azygos venous system
  • Thoracic duct
  • Para-aortic, oesophageal and paraspinal nodes
• Contents of Middle Mediastinum


  • Heart and pericardium
  • Nerves
  • Lymph nodes
  • Great vessels