"Brain Endothelium"

    When considering the vasculature of the brain, there are two important considerations: 1) conduit vessels, and 2) exchange vessels. The conduit vessels must - under all circumstances - deliver adequate oxygen to the brain (hence, the use of autoregulation). The exchange vessels must maximize diffusion of oxygen (high surface area, thin wall, narrow lumen), protect against fluctuations in blood composition (blood brain barrier), and allow for transportation of critical nutrients (special transporters). The blood brain barrier is composed of three elements: 1) physical, 2) enzymatic, and 3) efflux. The blood brain barrier arises in embryogenesis via angiogenesis and in the adult is largely but not exclusively regulated by the tissue microenvironment (Pericytes, gill cells). From a clinical standpoint, the blood brain barrier may become disrupted in many diseases (stroke, HIV, Alzhemiers, etc), leading to plasma leakage, edema and accentuation of symptoms. On the other hand, the barrier poses a significant challenge to drug discovery/delivery