blood-brain barrier

noun

ˈbləd-ˈbrān- How to pronounce blood-brain barrier (audio)
: a naturally occurring barrier created by the modification of brain capillaries (as by reduction in fenestration and formation of tight cell-to-cell contacts) that prevents many substances from leaving the blood and crossing the capillary walls into the brain tissues

Examples of blood-brain barrier in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
These proteins are usually flushed into the bloodstream through the blood-brain barrier. — Devika Rao, TheWeek, 26 June 2026 Scientists around the world engineered viruses that could slide through the blood-brain barrier that walls off our most vital organ from the rest of the body. — Jason Mast, STAT, 12 May 2026 This tipped the scientists off that there must be some molecule from the cancerous cells that can cross the blood-brain barrier and inflict good, not harm. — New Atlas, 29 Jan. 2026 Even when promising drugs are identified, delivering them to the brain is difficult due to the blood-brain barrier. — Adaira Landry, Forbes.com, 26 Feb. 2026 See All Example Sentences for blood-brain barrier

Word History

First Known Use

1934, in the meaning defined above

Time Traveler
The first known use of blood-brain barrier was in 1934

Rhymes for blood-brain barrier

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Browse Nearby Words

blood-borne
blood-brain barrier
blood brother
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Cite this Entry

“Blood-brain barrier.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/blood-brain%20barrier. Accessed 7 Jul. 2026.

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Medical Definition

blood-brain barrier

noun
: a naturally occurring barrier created by the modification of brain capillaries (as by reduction in fenestration and formation of tight cell-to-cell contacts) that prevents many substances from leaving the blood and crossing the capillary walls into the brain tissues
—abbreviation BBB

More from Merriam-Webster on blood-brain barrier

Britannica.com: Encyclopedia article about blood-brain barrier

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