Microvascular Geometry in the Brain of the Lizard Trachydosaurus-Rugosus

Abstract

The vasculature and microvasculature in the central nervous system of the lizard Trnchydosaurus rugosus was examined by means of scanning electron microscopy of vascular corrosion casts. The arterial supply to the brain is from paired internal carotids. Secondary branches from these feeder arteries form a network over the surface of the lizard brain, giving rise to artery-vein vessel pairs. The vessel pairs bend at right angles to the brain surface, giving rise to terminal arteriole-venular pairs which penetrate the brain substance. Capillaries arise at fairly regular intervals along the vessel pairs, each originating from the arteriole and terminating in the venule at a site contiguous with its origin from the arteriole. In this way all of the capillaries in the central nervous system of the lizard form countercurrent loops. Anastomotic connections between arteriole-venular pairs do not occur, each arterial vessel being an end artery.