Cortical blood vessels of the human brain.

The study is divided into two parts. (a) Superficial or pial vessels: Arterioles and venules at the gyrus surface as well as their mode of penetration into or emergence from nervous tissue is described. The absence of pial capillaries is noted. Arterial and venous anastomoses are described whereas arteriovenous anastomoses were not encountered. In particular, the relationship of superficial vessels to the arachnoid was studied. (b) Intracortical vessels: Arteries and veins were divided into 5 groups according to their degree of cortical penetration. Considering its density, the vascular network of the cortex was divided into 4 vascular layers. A correlation between these layers and the cellular layers was established. Problems in distinguishing between arteries and veins, the geometric disposition of cortical vessels, different types of anastomoses and particular vascular features whose significance remains unclear, are discussed.