This study was supported by grants 3.5.68 and 3.682.71 from the Swiss National Science Foundation.
The postnatal growth of the rat lung III. Morphology†
Article first published online: 27 JAN 2005
Copyright © 1974 Wiley-Liss, Inc.
The Anatomical Record
Volume 180, Issue 1, pages 77–98, September 1974
How to Cite
Burri, P. H. (1974), The postnatal growth of the rat lung III. Morphology. Anat. Rec., 180: 77–98. doi: 10.1002/ar.1091800109
- Issue published online: 27 JAN 2005
- Article first published online: 27 JAN 2005
- Manuscript Accepted: 5 FEB 1974
- Manuscript Received: 2 OCT 1973
In order to investigate the postnatal growth of the gas exchange apparatus, the lungs of rats aged 1, 4, 7, 10, 13, and 21 days were fixed by intra-tracheal instillation of glutaraldehyde. The analysis and interpretation of the morphological changes observed by light and electron microscopy were based on the results of previous morphometric and autoradiographic studies performed on the same material.
The newborn rat has no alveoli, but breathes with smooth walled air channels and saccules, which correspond to the prospective alveolar ducts and alveolar sacs, respectively. The bulk of alveoli are formed between days 4 and 13 by a rapid outgrowth of secondary septa from the primary septa present at birth. The arrangement of elastic fibers during this period suggests that these may play a role in septal outgrowth. Based on ultrastructural observations a model is described for the capillarisation of the secondary septa. Some evidence is given that alveoli may also be formed by outpouchings in the walls of terminal bronchioles.
Primary and secondary septa have initially an immature appearance. They both show an apparently double capillary network, whereas the mature interalveolar septum is just wide enough to accommodate a single capillary. Possible mechanisms for this structural transformation which occurs within three weeks after birth are discussed.