barrier


Also found in: Dictionary, Thesaurus, Legal, Financial, Encyclopedia, Wikipedia.
Related to barrier: Barrier methods

barrier

 [bar´e-er]
1. an obstruction.
2. a partition between two fluid compartments in the body.
3. a covering used to prevent contact with body fluids.
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 see blood-brain barrier.
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.
barrier methods contraceptive methods such as condoms and diaphragms in which a plastic or rubber barrier blocks passage of spermatozoa through the vagina or cervix. See discussion under contraception.
placental barrier the tissue layers of the placenta which regulate the exchange of substances between the fetal and maternal circulation.

bar·ri·er

(bar'ē-er),
1. An obstacle or impediment.
2. In psychiatry, a conflictual agent that blocks behavior that could help resolve a personal struggle.
3. In psychotherapy, anything that acts as an impediment to the insight, constructive change, healing, and growth of a patient (for example, an unhealthy or primitive defense mechanism; secondary gain; conflicted ambivalence; unconscious motivation derived from residual conflict from an earlier developmental stage; stubbornness; lack of ability to detach, observe, or analyze).
[M.E., fr. O.Fr. barriere, fr. L.L. barraria]

barrier

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

barrier

(băr′ē-ər)
n.
1. Physiology A membrane, tissue, or mechanism that blocks the passage of certain substances.
2. Ecology A physical or biological factor that limits the migration, interbreeding, or free movement of individuals or populations.

barrier

[ber′ē·ər]
Etymology: ME, barrere
1 a wall or other obstacle that can restrain or block the passage of substances. Barrier methods of contraception, such as the condom or cervical diaphragm, prevent the passage of spermatozoa into the uterus. Membranes and cell walls of body tissues function as screenlike barriers to permit the movement of water or certain other molecules from one side to the other while preventing the passage of other substances. Skin is an important barrier that protects against the entry of microorganisms and the exit of body fluids. Barriers in kidney tissues adjust automatically to regulate the retention or excretion of water and other substances according to the needs of organ systems elsewhere in the body.
2 something nonphysical that obstructs or separates, such as barriers to communication or compliance.
3 (in radiography) any device that intercepts beams of x-rays. A primary barrier is one that blocks the passage of the useful x-ray beam, such as the walls and floor. A secondary barrier is one that intercepts only leakage and scattered x-ray emissions. An example is the ceiling.

barrier

Physiology
A physical or functional hurdle which a substance or cell must surmount or circumvent to have free access to a tissue or site in the body.

Social medicine
An impediment in access to a service or activity, defined in the context of the Americans with Disabilities Act (ADA), which may be architectural (e.g., requiring widened doors, wheelchair ramps and others) or communication-related (e.g., linguistic barrier, vision defects).

According to the ADA, the existance of barriers may require an employer to make reasonable accomodations in the form of obtaining an interpreter or braille forms (e.g., for paperwork), or by altering the physical layout of an office or work space.

barrier

Physiology A physical or functional hurdle which a substance or cell must surmount or circumvent to have free access to a tissue or site in the body. See Blood-brain barrier, Bone marrow barrier Social medicine An impediment in access to a service or activity, defined in the context of the Americans with Disabilities Act–ADA, which may be architectural–eg requiring widened doors, wheelchair ramps, and others or communication-related–eg linguistic barrier, vision defects. See Americans with Disabilities Act, Architectural barrier, Cultural barrier, Disability, Inequitable barrier, Reasonable accommodations.

bar·ri·er

(bar'ē-ĕr)
1. An obstacle or impediment.
2. psychiatry A conflictual agent that blocks behavior that could help resolve a personal struggle.
[M.E., fr. O. Fr. barriere, fr. L.L. barraria]

bar·ri·er

(bar'ē-ĕr)
An obstacle or impediment.
[M.E., fr. O. Fr. barriere, fr. L.L. barraria]

barrier

an obstruction; a partition between two fluid compartments in the body.

blood-air barrier
alveolocapillary membrane.
blood-aqueous barrier
the physiological mechanism that prevents exchange of materials between the chambers of the eye and the blood.
blood-brain barrier (BBB)
the barrier separating the blood from the brain parenchyma. See also blood-brain barrier.
blood-CSF barrier
differs from the blood-brain barrier anatomically, in that it consists of the epithelium of the choroid plexuses, but has similar permeabilities.
blood-gas barrier
alveolocapillary membrane.
barrier-retina barrier
endothelium of the retinal capillaries and cells of the retinal pigment epithelium form a nonfenestrated barrier between choroidal tissue fluid and retinal tissue fluid.
blood-synovial barrier
suggested by the presence of plasma proteins of small molecular size and catabolic products of articular cartilage in synovial fluid.
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. It provides an extravascular environment which is also adluminal and permits selective nourishment of spermatozoa.
barrier boot
a rubber boot worn by horses to protect the hoof against trauma.
barrier cream
a nonwettable cream used on the skin of the hands and arms to protect against staining and odor absorption when handling offensive materials, e.g. delivery of an emphysematous fetus.
gastric mucosal barrier
the poorly defined mechanism that prevents back diffusion of hydrochloric acid from the stomach into the tissues of the stomach wall.
skin barrier
the protective properties of skin and its relative impenetrability by noxious substances as well as medicaments; usually considered a function of keratinized epithelial cells aided by surface lipids.
barrier teat dip
material which leaves a physical protective coat on the teat between milkings, used mostly to protect against infection for long periods, e.g. during the dry period. Most contain acrylic, latex or collodion.
References in classic literature ?
Why, just think for a moment; with this red handkerchief on my head, with scarcely any shoes, no papers, and ten gold napoleons in my pocket, without reckoning what was there before -- making in all about two hundred francs, -- why, I should certainly be arrested at the barriers.
At other times, he turns the traps bottom upwards, by the same means, and occasionally even drags them to the barrier and conceals them in the mud.
Raoul was as calm as if he were handling a foil, instead of a sword; having retreated a step, he parried three or four fierce thrusts which De Wardes made at him, caught the sword of the latter within his own, and sent it flying twenty paces the other side of the barrier.
For the better part of two hours the trail paralleled the barrier, and then suddenly turned toward it through the roughest and seemingly most impassable country I ever had beheld.
Jimmy Hollis and Colin Short whiled away many an hour inventing schemes for surmounting the obstacle presented by the barrier cliffs, and making ridiculous wagers as to which one Tom Billings had in mind; but immediately we were all assured that we had raised Caprona, Billings called us together.
But, finally, after what seemed long ages to the impatient ape-man, he topped the barrier cliffs that hemmed the desolate valley, and below him lay the grim and awful ruins of the now hideous city of Opar.
Upon the fourth day of September, 1916, he set out with four companions, Sinclair, Brady, James, and Tippet, to search along the base of the barrier cliffs for a point at which they might be scaled.
For hundred of year the Byzantine Empire stood as a barrier against the Saracen hosts of Asia.
But, in spite of all this, Anne felt that there was always a barrier between Leslie and herself--a constraint that never wholly vanished.
Westward of the shores of America, a wide space of open ocean extends, with not an island as a halting-place for emigrants; here we have a barrier of another kind, and as soon as this is passed we meet in the eastern islands of the Pacific, with another and totally distinct fauna.
The Uruguay has formed an insuperable obstacle to its migration: although the broader barrier of the Parana has been passed, and the bizcacha is common in Entre Rios, the province between these two great rivers.
All his efforts to draw her into open discussion she confronted with a barrier which he could not penetrate, made up of a sort of amused perplexity.