blood-brain barrier

barrier /bar·ri·er/ (bar´e-er) an obstruction.

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alveolar-capillary barrier , alveolocapillary barrier see under membrane.

blood-air barrier  alveolocapillary membrane.

blood-aqueous barrier  the physiologic mechanism that prevents exchange of materials between the chambers of the eye and the blood.

blood-brain barrier , blood-cerebral barrier the selective barrier separating the blood from the parenchyma of the central nervous system. Abbreviated BBB.

blood-gas barrier  alveolocapillary membrane.

blood-testis barrier  a barrier separating the blood from the seminiferous tubules, consisting of special junctional complexes between adjacent Sertoli cells near the base of the seminiferous epithelium.

placental barrier  term sometimes used for the placental membrane, because it prevents the passage of some materials between the maternal and fetal blood.

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blood-brain barrier

n. Abbr. BBB

A physiological mechanism that alters the permeability of brain capillaries so that some substances, such as certain drugs, are prevented from entering brain tissue, while other substances are allowed to enter freely.

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Blood-brain barrier

A blockade of cells separating the circulating blood from elements of the central nervous system (CNS); it acts as a filter, preventing many substances from entering the central nervous system.

Mentioned in: Lyme Disease

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blood-brain barrier (BBB)

Etymology: AS, blod + bragen + ME, barrere

an anatomic-physiologic feature of the brain thought to consist of walls of capillaries in the central nervous system and surrounding astrocytic glial membranes. The barrier separates the parenchyma of the central nervous system from blood. The blood-brain barrier prevents or slows the passage of some drugs and other chemical compounds, radioactive ions, and disease-causing organisms such as viruses from the blood into the central nervous system.

Blood-brain barrier

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blood-brain barrier,

n barrier formed by epithelial cells in the capillaries that supply the brain and central nervous system. This barrier selectively allows entry of substances such as glucose, some ions, and oxygen, while blocking entry of other substances. Also called
BBB.

Blood-brain barrier.

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blood-brain barrier,

n an anatomic-physiologic feature of the brain thought to consist of walls of capillaries in the central nervous system and surrounding glial membranes. It prevents or slows the passage of some drugs, other chemical compounds, radioactive ions, and disease-causing organisms such as viruses from the blood into the nerve tissues of the central nervous system.

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blood-brain barrier 

A mechanism that prevents some substances in the blood from reaching the brain. It is achieved by brain capillaries, which unlike other capillaries elsewhere in the body, are composed of endothelial cells sealed together in continuous tight junctions and surrounded by astrocytes that contribute to the selective passage of substances. Lipid-soluble substances such as alcohol, caffeine, nicotine and most anaesthetics, as well as glucose, oxygen and water, pass rapidly into brain cells, whereas proteins, most antibiotics and ions do not enter or enter very slowly. The mechanism protects brain cells against harmful substances and pathogens. See central nervous system.

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blood-brain barrier

Physiology A selectively permeable structural and functional barrier that exists between the capillaries and the brain; water, O₂ and CO₂ readily cross the BBB, glucose is slower, Na+, K+, Mg++, Cl–, HCO₃– and HPO₄– require 3-30-fold more time to equilibrate with the CSF than with other interstitial fluids; urea penetrates very slowly; catecholamines and bile salts essentially do not cross the BBB–kernicterus is due to accumulation of bile salts in the brains of neonates whose BBB is yet immature; integrity of the BBB is impaired in hepatic encephalopathy