Microvasculature of the medulla oblongata in the Lyle's flying fox (Pteropus lylei).

The microvasculature of the medulla oblongata in 15 adult Lyle's flying foxes (Pteropus lylei) was elucidated by using the vascular corrosion cast technique combined with scanning electron microscopy. The study showed that the medulla received the main arterial supply from branches of the vertebrobasilar system. The supplied areas were divided into three groups: ventral, lateral and dorsal groups. All vessel groups gave off circumferential and perforating branches; moreover, these branches anastomosed with one another in two fashions: end-to-end and side-by-side arrangements. In addition, the ramifications of the branches were L and Y types. The L type was more frequently found than the Y one. The density of capillaries in the nuclei was greater than that in the area of nerve fibres. Numerous arterial sphincters and smooth muscle cells were observed. Furthermore, capillaries in the medulla were of the continuous type, whereas those in the area postrema were fenestrated. The venous drainage system of the medulla was classified into caudal, middle and rostral parts. All of them emptied into both the sigmoid sinus and internal jugular vein. It was concluded that these vascular patterns provide sufficient blood supply to the medulla oblongata of P. lylei when abrupt changes in the position of this bat occurs.