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81 Cards in this Set
- Front
- Back
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What ultimately happens to the chorionic cavity (or extraembryonic coelom)?
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It gets obliterated as the amniotic cavity expands and surrounds the entire developing embryo
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The region of uterus directly overlying the conceptus is called...
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Decidua capsularis
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What does the decidua capsularis do?
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Fuses with the opposing decidua parietalis, and ultimately disintegrates
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The side of the uterine cavity has what type of chorion that eventually degenerates?
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Smooth chorion or chorion laeve
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The chorionic villi over the decidua basalis is?
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Villous chorion or chorion frondosum
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Where is the placenta located?
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In the region containing the chorionic villi that overlies the decidua basalis
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The somatic mesoderm of the amnion and chorion will fuse, to make the...
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Amniochorionic membrane
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What membrane ruptures at birth so the baby can descend through the birth canal?
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Amniochorionic membrane
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What is the 'breaking of waters'?
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Amniotic fluid spilled when amniochorionic membrane ruptures
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Only the decidua capsularis degenerates
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Notes
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What is the chorionic plate?
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The region containing the stumps of the main stem villi
-1 inch thick at birth |
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The capillaries of the chorionic villi receive deoxygenated blood from...
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Umbilical arteries
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What are cotyledons?
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Pockets of maternal sinusoids that contain several villi
-About 10-38 pockets |
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How big is the mature placenta?
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6 inches in diameter and a few inches thick
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What is in the placental membrane that divides the maternal and fetal blood supplies?
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1) Capillary endothelium
2) Syncytiotrophoblast |
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Do fetal and maternal blood directly mix?
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No
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What is transported from the mother to fetus through the placenta (3)?
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1) Glucose (stored as glycogen, only in placental compartment)
2) Fatty acids and cholesterol 3) NH3 and lactate |
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What is insulinase?
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Prevents the transport of maternal insulin to the fetus
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What is Sulfatase?
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Transports estrogen precursors out from the fetus
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What are the 4 mechanisms of transport across the placenta?
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1) Simple diffusion
2) Facilitated diffusion 3) Active transport 4) Pinocytosis |
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What is transported by simple diffusion through the placenta?
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Water, CO2, oxygen, urea, drugs
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What substances are transported by facilitated diffusion across the placenta?
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Sugars, amino acids, and certain ions
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What substances use active transport in placental exchange?
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Amino acids, Ions
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What substances use pinocytosis in placental exchange?
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Proteins (IgG), lipids, viruses?
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Tears in placental exchange allow...
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Large substances or even intact cells to pass
-Not a normal mechanism |
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What % of maternal Cardiac Output passes through the placenta?
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10% (0.5-0.6 L/min)
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What is fetal blood flow in the placenta?
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0.4 L/min
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What type of hemoglobin is in maternal blood?
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Alpha-2 and Beta-2
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What type of hemoglobin is in fetal blood?
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Alpha-2 and gamma-2
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What is special about alpha-2 and gamma-2 hemoglobin?
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Greater affinity for oxygen
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External pressure (by doctor) to the abdomen above the pubis prevents blood loss, promotes formation of a hematoma (blood clot), and expulsion of the placenta
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Notes
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What is the "afterbirth"?
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The placenta separates from the uterus within the deciduas basalis and is expelled
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How is amniotic fluid produced?
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1) Dialysis of maternal and fetal blood
2) Fetal urine |
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What does amniotic fluid consist of?
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1) Mainly water
2) Lipids 3) Carbohydrates 4) Proteins like alpha-fetoproteins 5) Shed fetal cells (Amniocytes) 6) Transferrin 7) Fatty acids 8) Lysozyme 9) IgG and IgA |
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What do IgG and IgA do in amniotic fluid?
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Confer passive immunity
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Lysozyme acts against?
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Gram-positive bacteria
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Fatty acids act how against bacteria?
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Detergent action incompatible with the integrity of bacterial membranes
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What are 3 things the amniotic fluid provides the fetus?
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1) Mechanical and thermal buffering
2) Room for growth and movement 3) Protection from bacterial infection (isolated environment) |
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Alpha-fetoprotein in the amniotic fluid indicates what?
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Incomplete closure of the neural tube
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Cells in the amniotic fluid can tell you what?
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Sex and chromosomal abnormalities can be determined from the karyotype
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What are fraternal twins?
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Non-identical
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What are maternal twins?
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Identical
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A fused placenta can arise in either maternal or fraternal twins
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Notes
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Embryos that splite later in development form separate inner cell masses
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Notes
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Complications of multiple pregnancies arise with what?
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Embryos that share a single amniotic cavity
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If embryo division occurs in the embryonic disc, what happens?
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Single placenta and single amniotic cavity
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What are 3 risks of monozygotic, monoamniotic twins?
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1) Entangled umbilical cords
2) Conjoined twins 3) Parasitic twins ("fetus in fetu") -Foreign internal masses of tissue represent remains of parasitic tissue |
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There is a genetic link relating family history to multiple pregnancies
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Notes
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What is twin to twin transfusion (for both maternal and fraternal twins)?
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Differential blood supply to the twins
-Can cause oligohydramnios and polyhydramnios |
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What is oligohydramnios?
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-Decreased amniotic fluid
-Lower production of urine |
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What is polyhydramnios?
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-Increased amniotic fluid
-Greater production of urine |
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What is erythrocyte mosaicism?
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-In fraternal twins that have a fused placenta and shared fetal vasculature
-Both fetuses will obtain different populations of red blood cells derived from each other |
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What are methods for distinguishing maternal vs fraternal twins?
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1) Arrangement of chorionic and amniotic cavities
2) Presence of erythrocyte mosaicism 3) DNA sequence analysis 4) FISH 5) RFLP |
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When does pre-eclampsia occur?
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After week 32 of gestation
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What is eclampsia?
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Pre-eclampsia with convulsions
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What is pre-eclampsia or toxemia of pregnancy?
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-Pregnancy induced maternal hypertension
-Generalized constriction of maternal arteries that affects many organ systems |
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How common is pre-eclampsia?
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5% of women in their first pregnancy and 1-2% in others, worsened by smoking
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What is a consequence of pre-eclampsia?
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Spiral arteries of the myometrium and those extending into decidua basalis become narrow and conceptus does not receive adequate blood supply
-Slows development leading to subnormal weights at birth -Related to abnormalities in angiogenesis, possibly VEGF -Fetus should be delivered as soon as possible |
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What is Placenta abrupta?
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-Premature separation of the placenta
-associatied with maternal hypertension, pre-eclampsia/eclampsia |
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What is Placenta previa?
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-Placenta is attached to uterine wall close to or covering the cervix
-Associated with cervical pregnancy or an internal os pregnancy -May lead to early detachment of the placenta, complications with bleeding |
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What is Total Placenta Previa?
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-Covers the internal os of the cervix
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What is the normal amount of amniotic fluid present at full term?
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1 L
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In oligohydramnios, what's the volume of fluid?
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Abnormally low at 400 mL or less
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In polyhydramnios, what's the volume of fluid?
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Abnormally high at 2 L or more
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What causes oligohydramnios (6)?
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1) Placental insufficiency
2) Inadequate blood supply 3) Dysfunctional nervous system 4) Anencephaly 5) Renal agenesis 6) Blocked ureter or urethra or other problems with fetal urination |
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What causes polyhydramnios (5)?
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1) Reduced drinking
2) CNS malformation 3) Esophageal atresia 4) Tracheoesophageal fistula 5) Twin-to-twin transfusion |
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Polyhydramnios may lead to premature delivery
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Notes
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What is one thing that oligohydramnios can cause?
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Amniotic Band Syndrome and "fetal restraint"
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What are amniotic bands?
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-Loose folds or bands of amniotic tissue that lead to limb amputation/constrictions and facial defects
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What are some consequences of fetal akinesia or hypokinesia (caused by amniotic bands or myoneural dysfunction or oligohydramnios (5)?
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1) Lung hypoplasia
2) Facial anomalies 3) Congenital constrictures or limb amputations 4) Growth deficiencies 5) Microgastria (rare) |
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When can ultrasound first begin being used?
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Two weeks of development
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When can chorionic villus sampling first be done?
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Week 6
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When can maternal serum alpha-fetoprotein first be found?
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week 14
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When can amniocentesis first be done?
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Week 7
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What is amniocentesis?
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Collect amniotic fluid and fetal amniocytes for diagnostic/genetic testing
-1/200-1/400 cases lead to miscarriage -Used in conjunction with ulrasonography -Usually performed in 2nd trimester |
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What is alpha-fetoprotein?
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A glycoprotein synthesized by the fetal liver, yolk sac, and gut
-Levels initially rise and fall during pregnancy -May be used as an indication of gestational age |
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High levels of alpha-fetoprotein in amniotic fluid or maternal serum may indicate?
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Spina bifida or othe NTDs
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Reduced levels of alpha-fetoprotein are associated with...
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Down Syndrome
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There is a high rate of false positives with alpha-fetoprotein tests
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Notes
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What does increased nuchal thickness (translucency) and absence of nasal bone indicate in late first trimester?
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Down Syndrome
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A method has been recently developed to sample circulating fetal cells and DNA fragments from maternal blood. This allows the diagnosis of various genetic conditions such as Down syndrome, etc.
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Notes
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