Also found in: Dictionary, Thesaurus, Legal, Financial, Encyclopedia.
Related to placental barrier: Blood brain barrier
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.
the semipermeable layer of fetal tissue separating the maternal from the fetal blood in the placenta; composed of: 1) endothelium of the fetal vessels in the chorionic villi, 2) stromata of the villi, 3) cytotrophoblast (negligible after the fifth month of gestation), and 4) syncytiotrophoblast covering the villi; the placental membrane acts as a selective membrane regulating passage of substances from the maternal to the fetal blood.
Synonym(s): placental barrier
pla·cen·tal mem·brane(plă-sen'tăl mem'brān)
The semipermeable layer of fetal tissue separating the maternal from the fetal blood in the placenta; composed of: 1) endothelium of the fetal tissues in the chorionic villi, 2) stromata of the villi, 3) cytotrophoblast (negligible after the fifth month of gestation), and 4) syncytiotrophoblast covering the villi; the placental membrane acts as a selective membrane regulating passage of substances from the maternal to the fetal blood.
Synonym(s): placental barrier.
Synonym(s): placental barrier.
pertaining to or emanating from placenta.
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.
accumulations of mineral deposit especially around the vessels and in the allantois, a normal occurrence in most species.
the allantoic and amniotic cavities; called also amniotic and allantoic sac.
edema of the placenta, without necessarily any involvement of the fetus.
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.
the placenta of a viable fetus, escaped from the genital tract, can implant successfully to the peritoneum.
a placental hormone present in the cow's peripheral circulation at about 160 days of pregnancy; thought to have prolactin and growth-hormone capabilities.
are normal structures on the amnion in most species. They are foci of squamous epithelium.
manual removal per vagina, detaching the placenta from each caruncle in turn.
placental transfer of immunoglobulins
see placental barrier (above) and passive immunity.