The extensive distribution of cardiac musculature in the intrapulmonary veins of the musk shrew suggests a phylogenetically primitive trait that may contribute to the regulation of pulmonary blood circulation.
Extends phylogenetic insights into pulmonary vein musculature; leaves open relevance to human pulmonary hemodynamics.
The cardiac musculature of intrapulmonary veins was examined to elucidate its distribution pattern in the musk shrew, the primitive mammalian type, using by both light and electron microscopies. The musculature was distributed extensively from the hilum to the small veins less than 50 microns in diameter, suggesting that the phylogenic origin of this musculature may be traceable to the primitive mammalian types. Ultrastructure of cardiac myocyte in the intrapulmonary venous walls was essentially similar to that of left atrial myocyte. This suggests that the cardiac musculature may contribute to the regulation of pulmonary blood circulation. The abundance of large lipid droplets in both atrial and pulmonary myocytes was also observed and seemed to be the characteristic ultrastructure related to the physiological condition in this animal.
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Endo et al. (1992) studied this question.
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