Respiratory

Thoracic anatomy

  • The chest wall is composed of the sternum anteriorly and the rib cage and vertebrae posteriorly
  • It is made up of 12 ribs, intercostal spaces and the thoracic vertebra from T1-T12.
    • The first seven ribs articulate at the sternum.
    • Ribs 8,9,10 articulate with manubriosternal cartilage.
    • Ribs 11 and 12 are free floating and do not articulate anteriorly.
  • Inferiorly lies the dome shaped diaphragm which is supplied by the phrenic nerve.

Lung anatomy


  • Trachea
    • The trachea extends from cricoid cartilage to the bifurcation at the carina at the level of manubriosternal joint
    • Trachea in cross section is composed of C shaped cartilage rings deficient posteriorly closely related to oesophagus.
    • At the carina at the level of the sternal angle (T4/5) it bifurcates into right main bronchus and then left main bronchus. 
  • Bronchus
    • The right main bronchus is shorter, wider and more vertical than the left and so is the destination of aspirated material.
    • There is repeated branching until terminal bronchioles and alveoli.
  • Right lung
    • composed of 3 lobes
    • Upper, Middle, Lower
    • Transverse and oblique fissures.
  • Left lung
    • Composed of 2 lobes
    • Upper (+ lingula) and lower
    • Separated by the oblique fissure.
  • Hila
    • Medial surface of the lungs where the vessels, nerves and lymphatics all enter the lung
  • Bronchopulmonary segments
    • Lung can be divided into surgical define units each with their own segmental bronchus and artery and vein.
    • Airway branches below the terminal bronchioles receive their arterial supply from the bronchial arteries which originate as an aortic branch
  • Pleura
    • The Lungs are enveloped by visceral pleural and then a pleural space and then parietal pleura.
    • The pleurae are continuous. The pleural space contains only a small amount of fluid and a virtual space.
    • Surface tension keeps the layers together and normal intrapleural pressure is between - 2 and - 5 cm H2O.
    • Parietal pleura is innervated by the intercostal and phrenic nerves so pleuritic pain can go to the shoulder and to the chest wall.

Airway levels - multiple levels

  1. (Ventilator circuit and tubing and mask or ET tube at raised FiO2 or pressures) or Normal Atmosphere
  2. Nasal →
  3. Nasopharynx →
  4. Larynx →
  5. Trachea →
  6. R/L Main Bronchi →
  7. Lobar bronchi →
  8. Segmental Bronchi →
  9. Successive Small bronchi→
  10. Bronchioles →
  11. Terminal bronchioles →
  12. Respiratory bronchioles→
  13. Alveolar ducts and sacs →
  14. Alveoli