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Morphological peculiarities of respiratory compartments of arctic animal lungs
G S Shishkin1, N V Ustyuzhaninova
1Laboratory of Functional Morphology of Lung, Siberian Branch of the Russian Academy of Medical Sciences, Novosibirsk, Russia.
Background:
Morphological and ultrastructural peculiarities of interalveolar septa in endemic arctic animals (reindeer, polar fox, lemming) are compared with laboratory animals (rat,dog).
Methods:
For light microscopy, tissue samples were taken from the central and peripheral sections of all lobes of the right lung. They were fixed in 10% neutral formalin and embedded in paraffin. For electron microscopy, samples were taken from subpleural sections of the caudal lobe of the right lung, fixed in 4% paraformaldehyde for 24 hours, subsequently postfixed in 2% OsO4. for 2.0 hours. Samples were dehydrated in acetone and embedded in a mixture of Epon 812 and Araldite. Ultrathin sections were photographed at a magnification of x4,000. For each interalveolar septum, lengths and diameters were recorded and the squares of septa surface, air-blood barrier surface and the number of the structures were determined. The topography of capillaries and the ultrastructure of interstitium were described.
Results:
Acini in the arctic animals (reindeer, polar fox, lemming) are compact. In all lobes they are fully expanded and uniformly filled with air. There is no physiological atelectasis. Alveoli appear straight and homogeneous in form and size. In the polar fox, the quantity of interalveolar pores of Kohn is twice that in the dog. The number of pores in the lemming are similar to those in the rat but their size is 1.6 times greater in diameter. In arctic animals more capillaries connect with both alveolar surfaces by an air-blood barrier and simultaneously participate in the gas exchange of two adjoining alveoli. In the polar fox and lemming the thickness of the air-blood barrier is 1.3-1.4 times less than that in the dog and rat.
Conclusions:
The set of morpho-functional peculiarities of the acini of arctic animals allows for an increase in gas exchange in the respiratory compartments of the lungs and provides necessary oxygenation of arterial blood at a low partial pressure of oxygen in the alveolar gas.