Because respiratory bronchioles are generally clustered in the center of the secondary lobule, their destruction (proximal acinar destruction) is seen as a hole in the center of the lobule, and hence the synonym centrilobular emphysema (Figure 2).
Detailed morphometric analysis has extensively expanded our knowledge of airway alterations in both membranous and respiratory bronchioles, (14) and it has documented airway narrowing with inflammation and fibrosis, and loss of the peribronchiolar alveolar attachments.
Yousem et al (8) found "thick fibrous septa" around the respiratory bronchioles
in some of their RBILD cases, a description that fits RBF.
The interstitial sites with the greatest particle accumulation, in descending order of amount, in the monkeys are the alveolar septa, pleura, interstitium of respiratory bronchioles
, and perivascular interstitium.
Models of particle (aerosol) deposition have demonstrated the importance of respiratory bronchiole
and alveolar duct structures in particle deposition (26-29).
This paradigm suggested that any or all of the small cartilaginous airways and membranous or respiratory bronchioles
were structurally altered (remodeled in current COPD terminology) in cigarette smokers and that this remodeling induced turbulent flow and increased airway resistance despite the large cross-sectional area of the airways involved.
2] injures the respiratory tract and has its greatest effect upon respiratory bronchioles
(Chauhan et al.
Cigarette smoking produces inflammatory changes in small airways, especially respiratory bronchioles
leading to dilatation and destruction of the small airways.
A morphologic grading scheme for membranous and respiratory bronchioles
The 19th, 20th, and 21st are called respiratory bronchioles
and are different from preceding bronchioles in that their epithelium changes form pseudostratified ciliated columnar to squamus, nonciliated.
The stellate lesions are small, discrete, and centered around respiratory bronchioles
and adjacent small arteries, with intervening uninvolved lung parenchyma present.
We also describe the surprising finding of fibrotic lesions of the large bronchi, which is usually restricted to membranous and respiratory bronchioles
, in the context of chronic rejection with OB.