Breaching the Blood-Brain Barrier As the organ responsible for controlling and regulating all bodily functions, the brain is highly sensitive and is easily affected by changes in it's surroundings. That is why it should always be well-protected from injuries, infection, and even from slight fluctuations in the ion levels of the blood. Protecting the brain from invading materials is the role of the blood-brain barrier (BBB). Functions of BBB The BBB is a network of capillaries that supplies blood to the brain. Capillaries usually have very thin walls made of endothelial cells, with small spaces between each cell to allow the flow of materials to and from the capillaries. However, the capillaries in the brain are different. They have endothelial cells that are tightly packed together. Star-shaped glial cells called astrocytes also provide support to the endothelial cells by forming a layer around them  ...