barrier

barrier
1. An obstacle or impediment. 2. In psychiatry, a conflictual agent that blocks behavior that could help resolve a personal struggle. [M.E., fr. O.Fr. barriere, fr. L.L. barraria]
- blood-air b. the material intervening between alveolar air and the blood; it consists of a nonstructural film or surfactant, alveolar epithelium, basement lamina, and endothelium.
- blood-aqueous b. a selectively permeable b. between the capillary bed in the processes of the ciliary body and the aqueous humor in the anterior chamber of the eye; consists of two layers of simple cuboidal epithelium joined at their apical surfaces with junctional complexes.
- blood-brain b. (BBB) a selective mechanism opposing the passage of most ions and large–molecular weight compounds from the blood to brain tissue located in a continuous layer of endothelial cells connected by tight junctions; similar capillaries are found in the retina, iris, inner ear, and within the endoneurium of peripheral nerves.
- blood-cerebrospinal fluid b., blood-CSF b. a b. located at the tight junctions which surround and connect the cuboidal epithelial cells on the surface of the choroid plexus; capillaries and connective tissue stroma of the choroid do not represent a b. to protein tracers or dyes.
- blood-testis b. an occluding b. formed by Sertoli cells in the seminiferous tubules of the testis, which separates the more mature cells of spermatogenesis in the adlumenal compartment of the tubule from blood-derived products in the basal compartment.
- blood-thymus b. a sheath of pericytes and epithelial reticular cells around thymic capillaries that prevents the developing T lymphocytes of the thymus from being exposed to circulating antigens.
- incest b. in psychoanalysis, the learning or internalization of parental and social prohibitions against incest.
- placental b. SYN: placental membrane.

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bar·ri·er 'bar-ē-ər n
1) a material object or set of objects that separates, demarcates, or serves as a barricade see BLOOD-BRAIN BARRIER, PLACENTAL BARRIER
2) a factor that tends to restrict the free movement, mingling, or interbreeding of individuals or populations <behavioral and geographic \barriers to hybridization>

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bar·ri·er (barґe-ər) an obstruction.

Medical dictionary. 2011.

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  • Barrier — may refer to: * Automatic full barriers, railway * Barricade * Crash barrier, highway * Language barrier, culture/linguistics * Noise barrier, noise prevention * Road block * Separation barrier, prevents the movement of people across a certain… …   Wikipedia

  • Barrier — steht für Korallenriffe: Great Barrier Reef, Australien Belize Barrier Reef, in der Karibik Inseln: Great Barrier Insel, Neuseeländische Insel Little Barrier Island, Neuseeländische Insel Bauwerke: SAFER Barrier, Streckenbegrenzungsmauer auf… …   Deutsch Wikipedia

  • barrier — UK US /ˈbæriər/ noun [C] ► something that prevents something else from happening or makes it more difficult: barrier (to sth) »In an ideal world, there would be no barriers to the free movement of people between countries. → See also NON TARIFF… …   Financial and business terms

  • Barrier — Bar ri*er, n. [OE. barrere, barere, F. barri[ e]re, fr. barre bar. See {Bar}, n.] 1. (Fort.) A carpentry obstruction, stockade, or other obstacle made in a passage in order to stop an enemy. [1913 Webster] 2. A fortress or fortified town, on the… …   The Collaborative International Dictionary of English

  • barrier — (n.) early 14c., barere, from Anglo Fr. barrere, O.Fr. barriere obstacle, gatekeeper, from barre bar (see BAR (Cf. bar) (n.1)). First record of barrier reef is from 1805 …   Etymology dictionary

  • barrier — [n1] obstruction bar, barricade, blank wall, blockade, bound, boundary, confines, curtain, ditch, enclosure, fence, fortification, gully, hurdle, impediment, limit, moat, obstacle, pale, palisade, railing, rampart, roadblock, stop, trench, wall;… …   New thesaurus

  • barrier — ► NOUN 1) an obstacle that prevents movement or access. 2) an obstacle to communication or progress: a language barrier. ORIGIN Old French barriere …   English terms dictionary

  • barrier — I noun bar, barricade, bound, boundary, bulwark, check, confines, enclosure, encumbrance, fence, fortification, hindrance, hurdle, impediment, interference, limit, obstacle, obstruction, partition, prevention, preventive, prohibition, protective… …   Law dictionary

  • barrier — n barricade, *bar …   New Dictionary of Synonyms

  • barrier — [bar′ē ər, ber′ē ər] n. [ME barrere < OFr barriere < barre,BAR1] 1. Obs. a fortress, stockade, etc. for defending an entrance or gate 2. a thing that prevents passage or approach; obstruction, as a fence, wall, etc. 3. anything that holds… …   English World dictionary

  • barrier — n. 1) to erect, place, set up a barrier 2) to overcome, take a barrier (the horse took the barrier easily) 3) to break down; remove a barrier 4) the sonic, sound barrier (to break the sound barrier) 5) a crush (BE), police barrier 6) a cultural;… …   Combinatory dictionary

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