barrier /bar·ri·er/ (bar´e-er) an obstruction.
barrier
barrier
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.
bar·ri·er (b r  - r)n. 1. A boundary or limit. 2. An obstacle or impediment. 3. Something that separates or holds apart. 4. Something immaterial that obstructs or impedes behavior. 5. 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
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.
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.
How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content.
| ?Page tools | ||
|---|---|---|
|