Bidiscoidal placenta supplements a placenta with two separate portions attached to separate sites on the wall of the uterus, occasionally found in humans. Bilobate placenta a placenta consisting of two lobes. Synonym: dimidiate placenta bipartite placenta a placenta divided into two separate parts. Chorioallantoic placenta a placenta in which the allantoic mesoderm and vessels fuse with the inner face of the serosa to form the chorion. Circinate placenta a cup-shaped placenta. Placenta circumvallata a placenta whose membranes wrap over the edge of the fetal surface of the organ. Circumvallate placenta Placenta circumvallata. Cirsoid placenta a placenta with appearance of varicose veins. Cordiform placenta a placenta having a marginal indentation, giving it a heart shape. Placenta creta Placenta accreta. Deciduate placenta a placenta whose maternal part is shed with delivery. Dimidiate placenta bilobate placenta. Discoid placenta a placenta with a flat, circular shape. Double placenta a placental mass of the two placentae of a twin gestation.
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It bathes the chorionic villi and flows peripherally to the marginal sinus, which leads to uterine veins. Food molecules, oxygen, and antibodies pass into fetal blood of the villi; metabolic waste products pass from fetal blood into the mother's blood. Normally, there is no admixture of fetal and maternal blood. The placenta is also an endocrine organ. It produces chorionic gonadotropins, the presence of which in urine is the basis of one type of pregnancy test. Estrogen and progesterone are also secreted by the placenta. Abruption of placenta Abruptio placentae. Accessory placenta a placenta separate from the main placenta. Placenta accreta a placenta in which the cotyledons have invaded the uterine musculature, resulting in difficult or impossible separation of the placenta. Complications of manually separating the placenta include hemorrhage, damage to the uterus, and, in rare cases, hysterectomy. Synonym: placenta creta adherent placenta a placenta that remains adherent to the uterine wall after the normal period following childbirth. See: placenta accreta annular placenta a placenta that extends like a belt around the interior of the uterus. Synonym: zonary placenta battledore placenta a form of insertion of the umbilical cord into the margin of the placenta in which it spreads out to resemble a paddle or badminton racket.groene
, bearing many chorionic villi that interlock with the decidua basalis of the uterus, which constitutes the maternal portion. The chorionic villi lie in spaces in the uterine endometrium, where they are bathed in maternal blood and lymph. Groups of villi are separated by placental septa forming about 20 distinct lobules called cotyledons. Attached to the margin of the placenta is a membrane that encloses the embryo. It is a composite of several structures (decidua parietalis, decidua capsularis, chorion laeve, and amnion). At the center of the concave side is attached the umbilical cord through which the umbilical vessels (two arteries and one vein) pass to the fetus. The cord is approx. 50 cm (20.) long at full term. The mature placenta is 15 to 18 cm (6 to.) in diameter and weighs about 450 gm (approx. When expelled following parturition, it is known as the afterbirth. Maternal blood enters the intervillous spaces of the placenta through spiral arteries, branches of the uterine arteries.
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The presence of hcg in the clinic maternal blood and urine is an indicator of early pregnancy. The trophoblastic layer continues to infiltrate the maternal tissues with fingerlike projections, called chorionic villi. By the third month of pregnancy the placenta is able to secrete large amounts of progesterone, enough to relieve the corpus luteum of that function. At term the normal placenta is one seventh to one fifth of the weight of the infant. The maternal surface is lobulated and has a dark red rough, liverlike appearance. The fetal surface is smooth and shiny, covered with the fetal membranes, and marked by large white blood vessels beneath the membranes that fan out from the centrally inserted umbilical cord. The time between the infant's birth and the expulsion of the placenta is the third and last stage of labor. Placenta (plă-sen'tă) Fetomaternal organ of metabolic interchange between embryo or fetus and mother. It has a portion of embryonic origin, derived from the outermost embryonic membrane (villous chorion and a maternal portion formed by a modification of the part of the uterine mucosa (decidua basalis) in which the chorionic vesicle is implanted. At term, the human placenta is disc shaped, about 4 cm thick and 18 cm in diameter, and averages about one sixth to one seventh the weight of the fetus; its fetal surface is smooth, being formed by the adherent amnion, with the umbilical cord. A flat cake placenta (pla-sent'a ) (-sent'e?) plural.
Placentas or placentae (-tē). A membranous vascular organ that develops in female eutherian mammals during pregnancy, lining the uterine wall and partially enveloping the fetus, to which it is attached by the umbilical cord. Following birth, the placenta is expelled. A similar organ in marsupial mammals, consisting of a yolk sac attached to the uterine wall. An organ with similar functions in some nonmammalian animals, such as certain sharks and reptiles. Botany The part within the ovary of a flowering plant to which the ovules are attached. Placenta pləsentə Etymology: l, flat cake a highly vascular fetal organ that exchanges with the maternal circulation, mainly by diffusion of oxygen, carbon dioxide, and other substances. It begins to form on approximately the eighth day of gestation when the blastocyst touches the wall of the uterus and adheres. Placentation begins as the trophoblast is able to digest cells of the endometrium, causing a small erosion on the uterine wall in which an embryo nidates. Human chorionic gonadotropin (hcg which is chemically identical to luteinizing hormone, is secreted by the developing placenta and promotes survival and hormone production of the corpus luteum.
Deciduate placenta, deciduous placenta a placenta or type of placentation in which the decidua or maternal parts of the placenta separate from the uterus and are cast off together with the trophoblastic parts. Fetal placenta the part of the placenta derived from the chorionic sac that encloses the embryo, consisting of a chorionic plate and villi. Hemochorial placenta one in which maternal blood comes in direct contact with the chorion, as in humans. Maternal placenta the maternally contributed part of the placenta, derived from the decidua basalis. Placenta membrana´cea one that is abnormally thin and spread out over an unusually large area of the uterine wall. Placenta percre´ta placenta accreta with invasion of the myometrium to its peritoneal covering, sometimes causing rupture of the uterus. Placenta pre´via one located in the lower uterine segment, so that it partially or completely covers or adjoins the internal. Placenta spu´ria an accessory portion having no blood vessel attachment to the main placenta. Placenta succenturia´ta, succenturiate placenta an accessory portion attached to the main placenta by an artery or vein. Villous placenta one characterized by the presence of villi that are outgrowths of the chorion.
Placen - mf plusPlacenta reflex´a one in which the margin is thickened, appearing to turn back on itself. Placenta spu´ria an accessory portion without blood vessels connecting it with the main placenta. Placenta succenturia´ta an accessory portion with an artery and a vein connecting it with the main placenta. Placenta (plă-sen'tă fetomaternal organ of metabolic interchange between the embryo or fetus and mother. It has a portion of embryonic origin, derived from a highly developed area of the outermost embryonic membrane (chorion frondosum and a maternal portion formed by a modification of the part of the uterine mucosa (decidua basalis) in which the chorionic vesicle is implanted. Within the placenta, the chorionic villi, with their contained capillaries carrying blood of the embryonic circulation, are exposed to maternal blood in the intervillous spaces in which the villi lie; no direct mixing of fetal and maternal blood occurs, but the intervening tissue (the placental. At term, the human placenta is disc shaped, about 4 cm in thickness and 18 cm in diameter, and averages about 1/6-1/7 the weight of the fetus; its fetal surface is smooth, being formed by the adherent amnion, with the umbilical cord normally attached near. A flat cake placenta /placenta/ (plah-sen´tah). An organ characteristic of true mammals during pregnancy, joining mother and fetus, providing endocrine secretion and selective exchange of soluble bloodborne substances through apposition of uterine and trophoblastic vascularized acen´tal placenta accre´ta one abnormally adherent to the myometrium, with partial or complete absence of the. Circumvallate placenta one in which a dense peripheral ring is raised from the surface and the attached membranes are doubled back over the placental edge.
Premature separation of the placenta is an emergency. The maternal signs are monitored every 15 minutes and blood loss is evaluated. Fetal heart tones also manicure are monitored to detect fetal distress. The amount of bleeding is estimated and documented. Oxygen equipment should be at hand in the event signs of fetal distress indicate anoxia. Postpartal hemorrhage and infection are more likely in women who have had placenta previa. Placement of the placenta in the lower segment predisposes to more bleeding because that portion of the uterus does not contract as forcefully as the upper segment. Additionally, the misplaced placenta has enlarged its bed to compensate for its poor location, so that there is a larger denuded area after delivery of the placenta. The same denuded area is also more susceptible to infection because it is located near the cervical opening where infectious organisms may enter. Vaginal bleeding during pregnancy or labor is frightening for the mother. She will need reassurance and frequent explanations of what is happening to her throughout the period of monitoring and delivery. Some emotional stress can be alleviated by encouraging the mother to be aware of fetal movements and allowing her to listen to normal fetal heart sounds.
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The condition occurs with greater frequency in women who have had multiple pregnancies or are over. The exact cause is not known. With the onset of any contractions and cervical dilation, or when the cervix begins to dilate at the onset of labor and the upper and lower uterine segments differentiate, the placenta is stretched and pulled from the uterine wall, producing bleeding. The bleeding usually is abrupt and painless and may stop on its own. However, if capes it continues it can be life-threatening for the mother since it is maternal blood that is being lost. The life of the fetus is in jeopardy because of anoxia resulting from separation of the placenta from its blood supply. Diagnosis can be established by ultrasonography or radiologic placentography. Once diagnosis is made, treatment will depend on the gestational age of the fetus and the percentage of placenta covering the cervical. Cesarean delivery is recommended if 30 per cent or more of the opening is obstructed by the placenta. If there is minimal bleeding that stops on its own, the fetus is not in distress, and if the gestational age is such that continuing the pregnancy is necessary for delivery of a viable fetus, the pregnancy may be continued under careful monitoring in the. However, if the life of the mother or fetus is threatened by continued and excessive bleeding, delivery is indicated. Vaginal examinations are carried out in an operating room so that if hemorrhage does occur as a result of manipulation of the uterus, a cesarean section can be done immediately to remove the placenta, stop the bleeding, and deliver the child safely.
After birth of the beere infant the placenta is cast off from the uterus and expelled via the birth canal. Placenta accre´ta one abnormally adherent to the myometrium, with partial or complete absence of the decidua basalis. Battledore placenta one with the umbilical cord inserted at the edge. Placenta circumvalla´ta one encircled with a dense, raised, white nodular ring, the attached membranes being doubled back over the edge of the placenta. Placenta fenestra´ta one that has spots where placental tissue is lacking. Placenta incre´ta placenta accreta with penetration of the myometrium. Placenta membrana´cea one that is abnormally thin and spread over an unusually large area of the myometrium. Placenta percre´ta placenta accreta with invasion of the myometrium to the peritoneal covering, sometimes causing rupture of the uterus. Placenta pre´via low implantation of the placenta so that it partially or completely covers the cervical. Percentages are used to designate the amount of obstruction;. G., 100 per cent is total placenta previa, and 50 per cent indicates that about half the opening is obstructed.
Placenta definition of, placenta by medical dictionary
Placentas, placen´tae ). ) an organ characteristic of true mammals during pregnancy, joining mother and offspring, providing endocrine secretion and selective exchange of soluble bloodborne substances through apposition of uterine and trophoblastic vascularized parts. In anatomic nomenclature the placenta consists of a uterine and a fetal portion. The chorion, the superficial or fetal portion, is surfaced by a smooth, shining membrane continuous with the sheath of the umbilical cord (amnion). The deep, or uterine, portion is divided by deep sulci into lobes of irregular outline and extent (the cotyledons). Over the maternal surface of the placenta is stretched a delicate, transparent membrane of fetal origin. Around the periphery of the placenta is a large vein (the marginal sinus which returns a part of the maternal blood from the organ. The major function of the placenta is to allow diffusion of nutrients from the mother's blood into the fetus's blood and diffusion of waste products from the fetus back to the mother. This two-way exchange takes place across the placental membrane, which is semipermeable; that is, it acts as a selective filter, allowing some materials to pass through and holding back others. In the early months of pregnancy the placenta acts as a nutrient storehouse and helps to process some of the food substances that nourish the fetus. Later, as the fetus grows and develops, these metabolic functions of the placenta are gradually taken on by the fetal liver. The placenta secretes both estrogens and progesterone.