What Exactly Is the Blood Brain Barrier?

Our brains are choosy about what they let in, and that's thanks to the blood brain barrier. In this episode, Patrick explores how this anatomical separation between our blood and brain keeps us safe from potential harm.
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The heart pumps oxygenated blood through arteries into systemic circulation, then those arteries branch out into tinier and tinier blood vessels called capillaries that surround different tissues. Capillaries have really thin walls, and oxygen, carbon dioxide, and other compounds can diffuse through those walls to get in or out of the blood stream.

And just like any other organ, the central nervous system, which includes the brain and spinal cord, gets oxygen and nutrients from the blood. But these organs are a little more sensitive to changes in their direct environment, so they need a bit more security around their blood supply to keep themselves stable. That’s where the Blood Brain Barrier comes in.

It’s an anatomical separation between the brain’s capillaries and the fluid between brain tissue itself. It’s made of a few different structures including special endothelial cells, a sheath of connective tissue, and nervous tissue that surrounds those tiny blood vessels in the brain. This thing is purpose built to be a selectively permeable barrier, so let’s take a little tour, starting with the inside of the capillaries.

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Read More:
Getting cancer drugs into the brain
https://www.nature.com/articles/d41586-018-06707-4
“The blood–brain barrier (BBB), a unique assembly of blood vessels that filters what goes into and out of the brain, is responsible for this quirk. And it is also the main reason why treatments for cancer that work elsewhere in the body fail routinely when directed at the brain.”

The Blood Brain Barrier
https://faculty.washington.edu/chudler/bbb.html
“More than 100 years ago it was discovered that if blue dye was injected into the bloodstream of an animal, that tissues of the whole body EXCEPT the brain and spinal cord would turn blue. To explain this, scientists thought that a "Blood-Brain-Barrier" (BBB) which prevents materials from the blood from entering the brain existed.”

Blood-brain barrier chip performs human-like drug and antibody transport
https://news.harvard.edu/gazette/story/2019/06/wyss-institute-develops-technology-to-better-study-blood-brain-barrier/
“Wyss Institute scientists have developed chip technology that mimics the blood-brain barrier in humans. The new models will help researchers study drugs to treat cancer, neurodegeneration, and other diseases of the central nervous system.”

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This Seeker health series will dive deep into the cellular structures, human systems, and overall anatomy that work together to keep our bodies going. Using the visual structure and quick pacing of Seeker’s Sick series, these human bio-focused episodes will give a new audience an inside look on what’s happening inside all of us.

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