Our brain is an extremely complex and delicate organ. Our body fiercely protects it by holding onto things that help it and keeping harmful things out, such as bugs that can cause infection and toxins. It does that though a protective layer called the blood-brain barrier.
Here’s how it works, and what it means for drug design. Adults have roughly 30 trillion cells in their body. Every cell needs a variety of nutrients and oxygen, and they produce waste, which needs to be taken away.
Our circulatory system provides this service, delivering nutrients and removing waste. Where the circulatory system meets your cells, it branches down to tiny tubes called capillaries. These tiny tubes, about one-tenth the width of a human hair, are also made of cells.
But in most capillaries, there are some special features (known as fenestrations) that allow relatively free exchange of nutrients and waste between the blood and the cells of your tissues. One way to think about the way the circulation works is like a pizza delivery person in a big city. On the really big roads (vessels) there are walls and you can’t walk up to the door of the house and pass someone the pizza.
But once you get down to the little suburban streets (capillaries), the design of the streets means you can stop, get off your scooter and walk up to the door to deliver the pizza (nutrients). We often think of the brain as a spongy mass without much blood in it. In reality, the average brain has about 600 kilometres of b.