Scanning electron microscope study of the developing microvasculature in the postnatal rat lung.

Caduff, J. H.; Fischer, L. C.; Burri, P. H. (1986). Scanning electron microscope study of the developing microvasculature in the postnatal rat lung. Anatomical record: advances in integrative anatomy and evolutionary biology, 216(2), pp. 154-164. John Wiley & Sons, Inc. 10.1002/ar.1092160207

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During postnatal growth the parenchymal septa of rat lung undergo an impressive restructuring. While immature septa are thick and contain two capillary layers, mature septa are slender and contain a single microvascular network. Using the Mercox casting technique and scanning electron microscopy, we investigated the mode and the timing of the transformation of the pulmonary capillary bed. During the third postnatal week the parenchymal septa rapidly mature to match adult morphology. Even in adult lungs, however, remnants of the immature status are present: A capillary bilayer is regularly found at the base and the tip of the septa. Our observations support the concept that reduction of intervening tissue, partial fusion of the two capillary networks, and preferential growth lead to the mature vascular arrangement. The fact that true mature interalveolar septa show a denser capillary network than alveolar walls abutting onto pleura, bronchi, or larger vessels is consonant with the fusion theory. Towards the nonparenchyma, the capillary network surrounding every airspace had no counterpart to fuse with. From quantitative data it can be calculated that owing to lung growth, mesh size should increase more than four times between birth and adult age. The adult lung network, however, is denser than the one in young animals. This means that new meshes must be added during growth. We propose that small holes observed in sheet-like regions of the microvasculature enlarge to form new capillary meshes. With this mechanism of in-itself or intussusceptional growth, sprouting of individual capillary segments to increase network size is no longer needed.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Anatomy
04 Faculty of Medicine > Medical Education > Institute of Complementary and Integrative Medicine (IKIM)

UniBE Contributor:

Fischer, Lorenz, Burri, Peter Hermann


600 Technology > 610 Medicine & health
500 Science > 570 Life sciences; biology




John Wiley & Sons, Inc.




Lorenz Fischer

Date Deposited:

18 Aug 2014 11:33

Last Modified:

05 Dec 2022 14:34

Publisher DOI:


PubMed ID:



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