1. The structure of the lower respiratory tract
David Fishwick
Consultant Respiratory Physician
Honorary Professor of Respiratory Medicine
University of Sheffield

2. Main functions Gas exchange 20m2 gas exchange area per lung
Minute ventilation approx 5 litres
Cardiac output approx 5 litres per minute
Regional differences in ventilation and perfusion (blood supply)

3. Thoracic cage

4. Lower respiratory structure
Main Airways
Trachea
Main Bronchi
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

5. Lower respiratory structure
Main Airways
Trachea
Main Bronchi
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

6. Trachea Larynx to carina (5th thoracic vertebra, T5)
Oval in cross section
Pseudo stratified, ciliated, columnar epithelium
Goblet cells
Semicircular cartilages
Mobile (3 cm and 1cm, superior and inferior)

7. Lower respiratory structure
Main Airways
Trachea
Main Bronchi
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

8. Main bronchi Left and Right main bronchi Sharp division between these
The carina
R main bronchus more vertically disposed
1-2.5cm long, related to the R pulmonary artery
L main bronchus
5cm long, related to the aortic arch

9. Lower respiratory structure
Main Airways
Trachea
Main Bronchi
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

10. Lobar bronchi Lobar Bronchi (normal) Right Left Upper lobe Middle lobe
Lower lobe
Left
Upper lobe and lingular

11. Lower respiratory structure
Main Airways
Trachea
Main Bronchi
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

12. Segmental branches Segmental Bronchi Right
Upper lobe Apical, Anterior, Posterior
Middle lobe Medial and Lateral
Lower lobe Apical, Ant, Post, Med, Lat

13. Segmental branches Segmental Bronchi Left
Upper lobe Apico-posterior, Anterior
Lingular Superior and Inferior
Lower lobe Apical, Ant, Post, Lat

14. Segmental branches Segmental Bronchi Right
Upper lobe Apical, Anterior, Posterior
Middle lobe Medial and Lateral
Lower lobe Apical, Ant, Post, Med, Lat

15. Segmental branches Segmental Bronchi Right
Upper lobe Apical, Anterior, Posterior
Middle lobe Medial and Lateral
Lower lobe Apical, Ant, Post, Med, Lat

16. Segmental branches Segmental Bronchi Right
Upper lobe Apical, Anterior, Posterior
Middle lobe Medial and Lateral
Lower lobe Apical, Ant, Post, Med, Lat

17. Lower respiratory structure
Main Airways
Trachea
Main Bronchi
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

18. Bronchioles

19. Acinus Distal to the terminal bronchiole
Alveoli more profuse with increasing generation of subdivision
Ducts are short tubes with multiple alveoli
Interconnection between alveoli exist (pores of Kohn)

20. Alveoli Type I pneumocytes Pavement
Type II pneumocytes Surfactant producers
Alveolar macrophage
Basement membrane
Interstitial tissue
Capillary endothelial cells

21. Lung Innervation Controls many aspects of function
Smooth muscle tone, mucus gland secretion, vascular permeability, blood flow
Sympathetic
BRONCHODILATION
Parasympathetic
BRONCHOCONSTRICTION
NANC

22. The Lung Structure Main Airways Pleura Trachea Main Bronci
Lobar Bronchi
Segmental branches
Respiratory Bronchiole
Terminal Bronchiole
Alveolar Ducts and Alveoli
Pleura

23. Pleura 2 main layers, of mesodermal origin
Visceral Applied to the lung surface
Parietal Applied to the internal chest wall
Each a single cell layer
Small amount of fluid between
Continuous with each other at lung root
Parietal pleura has pain sensation
Visceral pleura has only autonomic innervation

24. Blood supply Bronchial and pulmonary circulations
L and R pulmonary arteries run from R ventricle
17 orders of branching
Elastic (>1mm ) and non elastic
Muscular (<1mm )
Arterioles (<0.1mm )
Capillaries