Adrenal Microvasculature in the Lylei's Flying Fox (Pteropus lylei)

Abstract

Objective: The purpose of this study was to elucidate the microvasculature of the adrenal glands in the Lylei’s flying fox.
Methods: The adrenal glands of the Lylei’s flying foxes were processed in the histological technique and vascular corrosion cast technique combined with the SEM.
Results: Upon reaching the gland, the adrenal arteries divided into the cortical and medullary arteries. Firstly, the cortical arteries gave off subcapsular and true cortical capillary plexuses. Few loop cortical arteries were observed. At the corticomedullary junction, true cortical capillary plexus formed two groups, large peripheral venous radicles and sinusoidal medullary capillary plexus. Secondly, the medullary arteries supplied the inner cortex and medulla as true medullary capillary plexus. Therefore, the medullary capillary plexus composed of branches from cortical and medullary arteries. The medullary capillary plexus became a tributary of deep venous radicle. Both peripheral and deep venous radicles drained into the collecting, central, and adrenal veins, respectively. Furthermore, some medullary capillary plexus directly drained into the central vein without gathering into the collecting veins.
Conclusion: Not only the microvascular connections in the cortex and medulla, but also several channels of the venous drainage were found in the glands of this animal model. Especially, the direct connections between the medullary capillary plexus and the central vein have not been demonstrated in other animal models. These direct routes may supply the sufficient blood to this organ, when the animal suddenly alters the positions. These findings also support the internal control of the cortex over the medulla. In addition, the pattern of adrenal microvascularization in this animal is similar to that in human. So that, this mammal is a suitable model for microvascular investigation.