* * *blood-brain barrier n 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 abbr. BBB
* * *the mechanism that controls the passage of molecules from the blood into the cerebrospinal fluid and the tissue spaces surrounding the cells of the brain. The endothelial cells lining the walls of the brain capillaries are more tightly joined together at their edges than those lining capillaries supplying other parts of the body. This allows the passage of solutions and fat-soluble compounds but excludes particles and large molecules. The importance of the blood-brain barrier is that it protects the brain from the effect of many substances harmful to it. A disadvantage, however, is that many useful drugs pass only in small amounts into the brain, and much larger doses may have to be given than normal. Brain cancer, for example, is relatively insensitive to chemotherapy, although drugs such as diazapam, alcohol, and fat-soluble general anaesthetics pass readily and quickly to the brain cells.
* * *blood-cerebral barrier the barrier system separating the blood from the parenchyma of the central nervous system. Its anatomical component consists of unique endothelial cells in the brain capillaries, having tight junctions without fenestrations and with few microvilli and few vesicles for fluid transport. Its physiologic component in part consists of enzymes unique to the brain endothelia and of active transport via carrier proteins.
Medical dictionary. 2011.
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blood-brain barrier — [blud′brān′] n. Physiol. the barrier created by the walls of the capillaries of the brain that prevents certain substances, as most proteins and drugs, from passing from the blood into the brain tissue and cerebrospinal fluid … English World dictionary
Blood-brain barrier — The blood brain barrier (BBB) is a metabolic or cellular structure in the central nervous system (CNS) that restricts the passage of various chemical substances and microscopic objects (e.g. bacteria) between the bloodstream and the neural tissue … Wikipedia
blood-brain barrier — noun a mechanism that creates a barrier between brain tissues and circulating blood; serves to protect the central nervous system the brain was protected from the large molecules of the virus by the blood brain barrier • Hypernyms: ↑barrier … Useful english dictionary
blood-brain barrier — the mechanism that controls the passage of molecules from the blood into the cerebrospinal fluid and the tissue spaces surrounding the cells of the brain. The endothelial cells lining the walls of the brain capillaries are more tightly joined… … The new mediacal dictionary
blood-brain barrier — blood′ brain′ bar rier n. phl a layer of tightly packed cells that make up the walls of brain capillaries and prevent many substances in the blood from diffusing into the brain • Etymology: 1940–45 … From formal English to slang
blood-brain barrier — noun Date: 1944 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… … New Collegiate Dictionary
blood-brain barrier — /blud brayn /, Physiol. a layer of tightly packed cells that make up the walls of brain capillaries and prevent substances in the blood from diffusing freely into the brain: passage across the cell membranes is determined by solubility in the… … Universalium
blood-brain barrier — The blood vessels of the brain (and the retina) are much more impermeable to large molecules (like antibodies) than blood vessels elsewhere in the body. This has important implications for the ability of the organism to mount an immune response… … Dictionary of molecular biology
blood-brain barrier — A network of blood vessels with closely spaced cells that makes it difficult for potentially toxic substances (such as anticancer drugs) to penetrate the blood vessel walls and enter the brain … English dictionary of cancer terms
blood-brain barrier — noun A structure in the central nervous system (CNS) that keeps various substances found in the bloodstream out of the brain while allowing in the substances essential to metabolic function, e.g. oxygen. Syn: hematoencephalic barrier … Wiktionary