The ultrastructure of capillary walls and perivascular space of the pineal gland in three representatives of suidae species.

The ultrastructure of capillary vessels and the perivascular space (PVS) of the pineal gland were investigated in the domestic pig, miniature pig, and wild boar. It has been ascertained that the capillaries of these animals have continuous thick walls without pores and fenestrations. In fetal period, capillaries with spacious lumina, bordered by 3 to 4 endothelial cells predominate. The PVS, as a rule wide open, contain nerve endings, pinealocyte process endings, and collagenous fibers which increase with age.