placental 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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placental barrier

n.

The semipermeable layer of tissue in the placenta that serves as a selective membrane to substances passing from maternal to fetal blood.

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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.

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placental

pertaining to or emanating from placenta.

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placental barrier

the placental separation of maternal and fetal blood which varies in its structure and permeability between the species. In general the more layers of cells between the two circulations the less permeable the membrane. In none of the domestic animals are significant amounts of immune globulins or erythrocyte antigens passed through the membranes unless the epithelium is damaged. See also placenta.

placental calcification

accumulations of mineral deposit especially around the vessels and in the allantois, a normal occurrence in most species.

placental cavities

the allantoic and amniotic cavities; called also amniotic and allantoic sac.

placental edema

edema of the placenta, without necessarily any involvement of the fetus.

placental hormones

the placenta in all species produces estrogens and progesterone. In the cow it also produces lactogen, a hormone that influences structural and functional aspects of milk production. In the mare the endometrial cups produce pmsg (now called eCG) which assists in the maintenance of pregnancy. The equine, feline and primate placentae also produce relaxin which has a similar action.

placental implantation

the placenta of a viable fetus, escaped from the genital tract, can implant successfully to the peritoneum.

placental inflammation

see placentitis.

placental lactogen

a placental hormone present in the cow's peripheral circulation at about 160 days of pregnancy; thought to have prolactin and growth-hormone capabilities.

placental mole

see mole.

placental plaques

are normal structures on the amnion in most species. They are foci of squamous epithelium.

placental removal

manual removal per vagina, detaching the placenta from each caruncle in turn.

placental transfer of immunoglobulins

see placental barrier (above) and passive immunity.