| blood-retinal barrier | Specialised nonfenestrated tightly-joined endothelial cells that form a transport barrier for certain substances between the retinal capillaries and the retinal tissue. (12 Dec 1998) |
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| blood-testis barrier | The membrane in the testis that separates sperm from the bloodstream. (09 Oct 1997) |
| placental barrier | The semipermeable layer of foetal tissue separating the maternal from the foetal blood in the placenta; composed of: 1) endothelium of the foetal vessels in the chorionic villi, 2) stromata of the villi, 3) cytotrophoblast (negligible after the fifth month of gestation), and 4) syncytial trophoblast covering the villi; the placental membrane acts as a selective membrane regulating passage of substances from the maternal to the foetal blood. Synonym: placental barrier. (05 Mar 2000) |
| incest barrier | In psychoanalysis, the learning or internalization of parental and social prohibitions against incest. (05 Mar 2000) |
| thermal barrier | <radiobiology> In magnetic mirror devices, this is a depression of electrostatic potential formed by enhancing ion loss in the region between the central cell and the positive potential plug. The thermal barrier significantly reduces the density requirements in the plug and lowers the overall power required to sustain the solenoidal plugging by thermally decoupling central cell electrons from the end plugs. (09 Oct 1997) |