blood-brain barrier

noun

ˈbləd-ˈbrān- 

: 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

This leakage disrupts the blood-brain barrier, a protective membrane that separates circulating blood from the brain tissue, leading to fluid build-up and increased pressure in the brain. —New Atlas, 30 Apr. 2025

The brains of people with dementia had more, though the researchers noted that might be because those brains have a more porous blood-brain barrier and are less able to clear toxins. —Nina Agrawal, New York Times, 8 Apr. 2025

The novel drug-delivery method that breaches the blood-brain barrier could be usedto treat a host of diseases that afflict millions — like Alzheimer's, Parkinson's and a deadly condition associated with cancer. —Kale Williams, Axios, 21 Apr. 2025

Once ingested by a human, methylmercury isn’t easily excreted and can quickly cross the digestive tract, the blood-brain barrier, and the placenta. —Mack Degeurin, Popular Science, 12 Feb. 2025

Word History

First Known Use

1934, in the meaning defined above

Rhymes for blood-brain barrier

• noncarrier
• carrier

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