Interstitial Disease

Abstract

The alveoli, conductive airways, and blood vessels of the lung are surrounded by the pulmonary interstitium. Figure 14.1 shows the anatomy of several secondary pulmonary lobules (or lobule). Recall that each lobule contains 3–25 acini. Notice that the interlobular septum defines the secondary pulmonary lobule. The peribronchovascular interstitium surrounds the pulmonary artery and accompanying bronchiole. The subpleural interstitium lines the inner aspect of the pleura. The interstitium is a continuum of dense elastic tissue and collagen throughout the lung that merges into the elastic component of the alveolar walls. It is not normally separately defined on the plain radiograph and becomes visible when disease increases its volume and/or radiographic density.