Placentation Flashcards
Decidua parietalis is the remainder of the ______ not directly in contact with the conceptus. Once d. capsularis degenerates, it leaves only ______ and _____ by mid-gestation.
Endometrium; d. parietalis; d. basalis
Anchoring villi of the basal plate forms columns of proliferating ________ and _____.
Cytotrophoblast cells; the Cytotrophoblastic Shell. The cytotrophoblasts break away and colonize decidua, and infiltrate the uterine vasculature.
_________ form where chorionic villi contact the decidua.
Anchoring villi
On the fetal surface of the placenta, you can see:
The umbilical cord, the amnion, and the chorion (how you know it is the fetal side).
When the placental barrier lessens with time, initially the capillaries were central but later capillaries appear at the margin, and the ________ layer is lost.
Cytotrophoblast
The chorion is made up of _______ and _______.
Chorion frondosum; chorion laeve
As the fetus grows, exchange across the placenta is enhanced by increased villous surface area (due to ______) and a thinner ________ (fewer cells separate maternal blood from fetal blood.
Branching; “Placental barrier”
Amniotic fluid is formed from:
Water in maternal and fetal circulation, approx. 1000 cc at birth
Progesterone:
Development and maintenance of decidua cells, prevents uterine contractions, made throughout gestation, *** made in sufficient amounts to take over for the corpus luteum after week 10
Decidua _______ is the decidua directly overlying the implanted conceptus.
Capsularis
In the chorionic plate, _________ are continuous with the umbilical cord.
Vascularized mesoderm. The chorionic plate is also lined with cytotrohphoblasts and syncytiotrophoblasts. Here the amnion tightly opposes the mesoderm and blood vessels from umbilical cord branch out across the chorionic plate to feed the main stem villi.
The villous chorion (frondosum) is the branched portion of the chorion that is in contact with the ________.
Decidua basalis
Remodeled blood vessels loose patency and remain dilated. They can transport an increased blood volume to the _________ due to their _____ and ______.
Intervillous space; high capacity; low resistance
The placenta is a _______ organ.
Fetomaternal
The Decidua Basalis forms the _______ of the placenta and remains with it at parturition.
Basal plate
HLA-G is not expressed by adult tissues except:
Thymic medulla
________ mediate exchanged with maternal blood.
Syncytiotrophoblasts
Transcervical Retrieval of Fetal Cells
Fetal cell is retrieved in the cervix via a PAP smear, non-invasive recovery of extravillous cytotrophoblast cells migrating from the placental anchoring villi to the cervix, can recover 1000-2000 cells any time during weeks 5-20. Fetal cells are isolated away from adult cervical cells by immunoaffinity for HLA-G on trophoblast cell surface. By collecting whole cells, the entire genome is obtained for genetic testing of fetal DNA
________ is renewed by fusion of proliferating cytotrophoblasts with the syncytium.
Syncytiotrophoblasts
Through the 8th week, _______ are present over the entire chorion.
Villi - associated with the decidua capsularis are stretched by growth and compressed until they lose their blood supply.
Fetal circulation: ______ fetal blood returns through venules in the villi to veins that connect to the umbilical vein.
Oxygenated
The maternal components of the placenta include:
The decidua - basalis, capsularis, and parietalis.
Amniotic fluid contains oligohydramnios, which is _____ amniotic fluid and polyhydramnios, which is _____ amniotic fluid.
Reduced (
The umbilical cord is comprised of (5):
- An outermost layer of amnion 2. A mucoid mesoderm (Wharton’s Jelly) 3. Two umbilical arteries - brings fetal blood from the heart to the placenta 4. One umbilical vein - beings blood from placenta back to fetal heart 5. Vitelline duct (only in segment closest to fetus) containing a. yolk sac stalk and b. two blood vessels
Dizygotic (non0identical twins):
- formed by two separate embryos due to ovulation of two oocytes 2. Commonly result of ovulation induction procedures 3. Hereditary basis 4. Will be implantation sites (2), each forming a separate placenta, amnion and chorion (but they may fuse) 5. SIblings with distinct genetic compositions
Chorionic villi contain _______ capillaries.
Fetal
During its expansion, the _______ ensheaths the connecting stalk.
Amnion
Fetal side of the placenta:
-Umbilical cord attached anywhere , but usually central -Amnion and chorion laeve both present -Amnion tight against placenta, covering the chorionic plate -Large blood vessels in chorionic plate (chorionic vessels)
The placenta is derived from the ______.
Chorion
Placental transport:
Gases: O2 and CO2 diffuse freely across partial pressure gradients (high to low), maternal blood at pO2 of 50 mmHg, fetal blood in villi at only 30 mmHg - so O2 diffuses toward fetal blood Nutrients: most cross freely Waste: products cross freely: CO2, urea, uric acid, bilirubin, creatinine Antibodies: IgG, but NOT other immunoglobulin classes, confers passive immunity to fetus Drugs: most by simple diffusion, how pathogens cross too
Oligohydramnios is associated with _____ blood flow to the placenta and often due to ________ of the amniochorionic membrane.
Low; premature rupture. Also occurs when fetal kidneys do not form or when urinary tract is obstructed (no urine is produced)
Fetal circulation: ________ fetal blood goes from the fetus through 2 umbilical arteries to the placenta.
Deoxygenated blood
Syncytiotrophoblast nuclei age and undergo apoptosis - forming clusters called _________. These are shed into the __________ and enter the maternal circulation, releasing fragments of fetal DNA (circulating cell-free fetal DNA).
Syncytial knots; intervillous space
Cytotrophoblast cells become “extravillous” and migrate into the _______ and maternal blood vessels.
Decidua
Chorionic plate
Fetal side
The extravillous cytotrophoblasts invade the _______. They also break down the vascular smooth muscle and displace the endothelial cells that line arteries.
Maternal arteries, penetrates as far as the upper third of the myometrium
________ on the apical plasma membrane (______) enhance exchange.
Microvilli; brush border
Amniotic fluid diffuses from _______ across the _____.
Decidua parietalis; amniochorionic membrane. The diffusion of fluid across the placenta is primarily from maternal blood and is exchanged with fluid in fetal lungs, intestines, and kidneys - fetal swallowing and excretion
Term placenta contains:
Ruptured amnion and chorion laeve, chorion frondosum, and umbilical cord
Which chorion stretches over the expanded amnion?
Chorion laeve (smooth)
The _______ is considered the floor of the placenta and is made up of:
Basal plate; decidua basalis
Endocrine functions of the placenta: Hormones that are secreted by the syncytiotrophoblasts:
- Human chorionic gonadotropin 2. Human placental lactogen 3. Progesterone 4. Estrogen
What is the leading cause of premature births?
Preterm rupturing of the amniochorionic membrane - the amnion contributes most of the strength to the barrier that contains the amniotic fluid
Branching of the chorionic villi _____ during gestation in order to provide a site of exchange between maternal and fetal circulation, bathe cells in maternal blood of the ___________.
Increases; intervillous space.
Polyhydramnios is caused by:
CNS disorders or mechanical blockage of the digestive tract (eg esophogeal atresia)
Exchange between the maternal and fetal circulation:
Takes places as the maternal blood moves toward the roof of the placenta and returns, bathing the chorionic villi, toward the floor of the placenta
The amniochorionic membrane is formed by:
As the amnion becomes filled with fluid, the chorionic cavity is displaced and the two membranes become closely apposed
Fetal death or injury may occur due to constriction by the ___________.
Umbilical cord. True knot formation - knot formed in cord can constrict blood flow, false knot - just a loop in blood vessels that is harmless. Fetal tissues can be destroyed by entanglement in the cord
The basal plate contains ______ and _____.
Anchoring villi; extravillous trophoblasts
Trophoblasts form a _______ epithelium of _______ on the basal lamina and _______ on the outer layer
Stratified; cytotrophoblasts; syncytiotrophoblasts
Which type of twins is formed by two separate embryos due to ovulation of 2 oocytes?
Dizygotic
Excess fluid and poor fetal swallowing can be seen in:
Polyhydroamnios
In 65% of monozygotic twins, separation occurs ____ blastocyst formation resulting in two inner cell masses.
During; each inner cell mass forms an amnion, but there is only ONE chorion, and therefore ONE PLACENTA formed from the trophoblast
Poor trophoblast survival and invasion (cause of preeclampsia) leads to:
No physiologic conversion of spiral arteries Poor blood flow to intervillous space Maternal blood pressure increases
The chorion laeve contains _______ mesoderm.
Avascular
Which is known as the villous chorion?
Chorion frondosum
Human chorionic gonadotropin:
Maintains the CORPUS LUTEUM in the first trimester
The _______ has the fetal side and maternal side of the placenta:
Chorion frondosum
Maternal side of placenta:
Cotyledons - cobbelstone appearance on surface Pieces of decidua - appear as a thin, skin-like covering over the cotyledons
Basal plate
Maternal side
Estrogen:
Enlargement of uterus, breasts, breast glands, external genitalia (for delivery)
In 1% of monozygotic twins, separation occurs ______ implantation within the embryonic disc after formation of the amnion.
After implantation - two fetuses form with a SINGLE amnion, with only one chorion and placenta. Fetus at risk for entanglement. Conjoined twins - incomplete separation of embryonic disc occurs
The _______ is known as the smooth chorion, where villi and vasculature are lost.
Chorion laeve
The functions of amniotic fluid in protecting the fetus (6):
- Buoyant medium for symmetrical growth 2. Prevents adhesion of amnion to embryo 3. Cushions against impacts to mother 4. Controls body temperature of fetus 5. Permits fetal movement and muscle development 6. Provides protection against infection
Which type of twins has 2 implantation sites, each forming a separate placenta, amnion and chorion?
Dizygotic
The villous chorion (chorion frondosum) is the ____ portion of the placenta.
Fetal
Which type of twins is formed by the separation of embryonic material within a single embryo arising from a single oocyte?
Identical (monozygotic)
The differentiation of extravillous cytotrophoblasts in the anchoring villi: extravillous cytotrophoblases migrate through the ______ and are identified here by the expression of ______.
Decidua; cytokeratin-7, which only cells derived from epithelium make cytokeratin-7 (CK7).
Circulating cell-free fetal DNA:
Non-invasive recovery of fetal DNA fragments released from SYNCYTIOTROPHOBLASTS nuclei shed into the intervillous space, sufficient quantities of DNA recovered from maternal plasma in weeks 8-10 (syncytiotrophoblast turnover - apoptosis in ST releases fetal DNA into the maternal blood at the intervillous space). Fetal DNA is about 5% of the total sequenced - using parental DNA samples, allelic polymorphisms are assessed to sort out maternal and fetal DNA sequences
The decidua basalis is derived from the _______ directly beneath the conceptus.
Endometrium
What procedure eliminates all symptoms of preeclampsia?
Complete removal of placenta
The smooth chorion is:
Chorion laeve
The placenta has a fetal and a maternal portion. The fetal components include:
Amniotic cavity (environmental control and protection) and a placenta for nutrition, protection, respiration, excretion, and hormone production
In 35% of monozygotic twins, separation occurs _______ blastocyst formation leading to 2 separate blastocysts.
Before. So this is morphologically the same as dizygotic twins - genetic testing is required to distinguish the two
________ is the site of exchange with maternal blood.
Chorionic villi
The intervillous space is supplied by oxygenated blood by:
Spiral uterine arteries that empty through the placental floor. The space is filled with 150 cc of maternal blood and then the deoxygenated blood is drained by uterine veins
The intervillous space is between the _______ and the ________.
Chorionic plate and basal plate.
What determines how the placenta and fetal membranes appear?
The point in development that separation occurs
Which type of twins has a hereditary basis?
Dizygotic
Extravillous cytotrophoblasts also express the major histocompatibility complex:
human leukocyte antigen-G (HLA-G). Class I MHC (HLA-A and HLA-B) are downregulated.
Amniocentesis:
Invasive procedure to collect amniotic fluid performed beginning of week 14, transabdominal retrieval of amniotic fluid, ultrasound guided needle - 10 cc of amniotic fluid, pregnancy loss ~1%. Fetal cells in the fluid are cultured to obtain fetal DNA - PCR - sequencing - microarray, chromo nubmer by karyotype analysis
The number of __________ decreases in the villi by the third trimester.
Cytotrophoblasts
Which decidua degenerates?
D. capsularis
Human placental lactogen:
breast development, fetal protein deposition, decreased maternal glucose utilization
In early placenta, the __________ is considered the “roof” of the placenta.
Chorionic plate
Because the blood flow to the placenta is poor, the mother’s circulatory system compensates by increasing blood pressure. Preeclampsia, which produces ______ and ______ , accounts for about ____ of premature births.
Hypertension and kidney dysfunction (proteinuria); 15%. It also effects 5-7% of all pregnancies, accounts for 40-80% of maternal deaths (significant morbidity and mortality)
The pregnancy disorders, preeclampsia and intrauterine growth retardation are a result of:
The failure of the extravillous cytotrophoblasts to remodel the maternal vasculature
Early placenta has:
Chorionic plate, chorionic villi, and a basal plate
Chorionic Villus Sampling:
Invasive procedure done at 10 weeks, retrieve fragments of the chorionic villi - transabdominal or transcervical, guided by ultrasound, pregnancy loss ~1-2%. In the tissue fragments, DNA is assessed directly and fragments are cultured to obtain more cells.
Prenatal genetic diagnosis: suspected pregnancies are tested genetically. What are reasons to screen?
- Diagnose inherited disease carried by parent 2. Screen for chromosome number anomalies in women over 35 3. Determine complete genomic sequence for personalized medicine in the future **Testing requires DNA from the fetus
HLA-G protects against the:
Maternal autoimmune attack because fetal cells have unique paternally-inherited antigens and could be recognized as non-self by the maternal immune system
