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30 Cards in this Set

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