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 occurs when cancer cells migrate through the blood-brain barrier. —Charna Flam, People.com, 7 Mar. 2025

Proteins that are mostly found in the brain were detected in his bloodstream, suggesting that the blood-brain barrier had lost some of its integrity. —Dhruv Khullar, The New Yorker, 10 Feb. 2025

Cancer cells can enter the brain by crossing the blood-brain barrier, a protective mechanism designed to keep harmful substances out of the brain. —Julie Scott, Msn, Anp-Bc, People.com, 28 Feb. 2025

In addition to a thick skull, the blood-brain barrier (BBB), a natural protective membrane, prevents microscopic intruders such as toxins and pathogens from entering the nervous system. —Jenny Lehmann, Discover Magazine, 26 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