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30 Cards in this Set
- Front
- Back
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What are the three trophoblast types that compose the placenta?
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Cytotrophoblasts, Intermediate trophoblasts, and Syncytiotrophoblasts.
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What is a cytotrophoblast?
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A primitive cell type that gives rise to intermediate trophoblasts and syncytiotrophoblasts.
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What are intermediate trophoblasts?
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They invade the uterus and its vessels and also produces some pregnancy hormones.
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What are syncytiotrophoblasts?
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They line the placental villi and provide transfer from maternal to fetal compartment.
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What is the functional unit of the placenta?
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The chornionic villi.
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What are the layers of the fetal membrane?
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The amnion (inner) and the chorion (outer)
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What are two main functions of the placenta?
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During the 1st trimester, it produces hormones. During the 2nd and 3rd trimesters, it has a nutrient transfer role.
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List the different mechanisms of transport across the placenta and what they transfer.
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1. Passive Diffusion = extracellular/transcellular diffusional transport w/ permeability determined by size, lipid solubility, ionic charge, and maternal serum protein binding.
2. Active Transport = Glucose, certain aa's, Ca++ 3. Endocytosis/Exocytosis = IgG, LDL |
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What is the role of the placenta regarding waste products?
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It acts to elmininate waste products; because the fetal liver is immature, it elminates bile acids and biliary pigments.
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What is the respiratory function of the placenta?
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The membrane is highly permeable to respiratory gases. Exchange is determined by partial pressure gradient b/w maternal & fetal circulations and limited by blood flow.
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In monozygotic twinning, how many chorions and amnions are there if the fertilized ovum cleaves during the first 2 to 3 days?
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Two chorions and two amnions (separate placentae).
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In monozygotic twinning, how many chorions and amnions are there if the fertilized ovum cleaves on the 3rd day?
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Two chorions and two amnions (fused placentae).
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In monozygotic twinning, how many chorions and amnions are there if the fertilized ovum cleaves b/w the 3rd and 8th day?
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One chorion and two amnions.
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In monozygotic twinning, how many chorions and amnions are there if the fertilized ovum cleaves b/w the 8th and 13th day?
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One chorion and one amnion.
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In monozygotic twinning, how many chorions and amnions are there if the fertilized ovum cleaves b/w the 13th and 15th day?
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One chorion and one amnion, but the twins are conjoined.
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What is characteristic of a dichorionic diamniotic twin pregnancy upon ultrasound?
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The twin peak or lambda sign.
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What are the risks assoc w/ monochorionic, monoamniotic twins?
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They carry the greatest pernatal mortality risk; they can have entangled cords, which gives problems such as growth restriction, neurologic morbidity, etc.
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What are the risks assoc w/ monochorionic, diamniotic twins?
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Vascular anastomoses b/w the two, unequal distribution of blood occurring b/w the two twins.
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What is placenta previa?
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The implantation of the placenta over the cervical os.
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What happens in total placenta previa?
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The cervical os is completely covered by the placenta.
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What happens in partial placenta previa?
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It is partial occulsion of the cervical os by the placenta.
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What happens in marginal placenta previa?
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The encroachment of the placenta to the margin of the cervical os.
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What is placenta acreta?
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The placenta is attached directly to the myometrium. (Most common)
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What is placenta increta?
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The placenta invades the myometrium.
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What is placenta percreta?
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The placenta penetrates the myometrium. (Least common)
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What are risk factors for placenta previa?
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Previous placental previa, multiple gestation, and smoking.
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What is vasa previa?
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The fetal vessels traverse the membranes in the lower uterine segment and cover the cervical os.
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What is succenturiate placenta?
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Vascular communications b/w placental cotyledons.
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What is placental abruption and what are risk factors for it?
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Premature separation of the normally implanted placenta. Risk factors include HTN, maternal trauma, multiple gestation, smoking, hydramnios, cocaine use.
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What does "hemochorioepithelial type" mean in regard to the placenta and fetal membranes?
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No direct mixing of blood.
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