Flashcards in Placenta, Amniotic Fluid, and Umbilical Cord - HY Deck (101):
3 Stages of villous chorion?
1. Primary chorionic villi.
2. Secondary chorionic villi.
3. Tertiary chorionic villi.
The MATERNAL component of the placenta?
1. Decidua basalis.
2. Decidua parietalis.
3. Decidua capsularis.
Derived from the endometrium of the uterus located between the BLASTOCYST and the MYOMETRIUM.
Includes ALL portions of the endometrium other than the site of implantation.
Decidua basalis + decidua parietalis fate afterbirth?
Shed as part of the afterbirth.
What is the decidua capsularis?
The portion of the endometrium that covers the blastocyst and separates it from the uterine cavity.
What is the fate of the decidua capsularis?
Becomes attenuated and degenerates at week 22 of development because of reduced blood supply.
The maternal surface of the placenta is characterized by?
8-10 compartments = COTYLEDONS (impairing a cobblestone appearance), which are separated by decidual (placental) septa.
Gross morphology of the maternal surface?
Dark red in color and oozes blood due to torn maternal blood vessels.
When is the placenta formed?
When the embryo invades the endometrium of the uterus and when the trophoblasts forms the VILLOUS CHORION.
Fetal component of the placenta - Consists of?
Tertiary chorionic villi derived from BOTH the trophoblast + extraembryonic mesoderm --> Collectively known as the VILLOUS CHORION.
The villous chorion develops most prolifically ...?
At the site of the DECIDUA BASALIS.
The villous chorion is in contrast to an area of ...?
NO VILLOUS development known as the SMOOTH CHORION --> Related to the DECIDUA CAPSULARIS.
The fetal surface of the placenta is characterized by ...?
The well-vascularized chorionic plate containing (fetal) blood vessels.
Fetal surface gross appearance?
The fetal surface has a smooth, shiny, light-blue or blue-pink appearance (because the amnion covers the fetal surface) + 5-8 large chorionic (fetal) blood vessels should be apparent.
Velamentous placenta occurs ...?
When the umbilical (fetal) blood vessels abnormally travel through the amniochorionic membrane BEFORE reaching the placenta proper.
If the umbilical (fetal) blood vessels cross the internal os, a serious condition called ... exists.
Why is vasa previa a serious condition?
If one of the umbilical (fetal) blood vessels ruptures during pregnancy, labor, or delivery, the fetus will bleed to death.
Placenta previa occurs when ...?
The placenta attaches in the LOWER PART of the uterus, covering the internal os.
The placenta normally implants in the ... wall of the uterus.
Complications of placenta previa?
1. Uterine (maternal) blood vessels rupture during the LATER PART of pregnancy as the uterus begins to gradually DILATE.
2. The mother may BLEED TO DEATH.
3. The fetus will also be placed in jeopardy due to compromised blood supply.
Placenta previa - Why C-section?
Because the placenta blocks the cervical opening.
Placenta previa is a CLASSIC CAUSE of ...?
3rd TRIMESTER BLEEDING. (Ectopic pregnancy is a CLASSIC CAUSE of 1st trimester bleeding).
Placenta accreta/increta/percreta - Occurs when ...?
A placenta implants on the MYOMETRIUM --> Accreta.
Deep into the MYOMETRIUM --> Increta.
Through the wall of the UTERUS --> Percreta.
Complications of placenta percreta?
Retained placenta + Hemorrhage and may lead to UTERINE RUPTURE.
Risk factors for placenta accreta/increta/percreta?
1. Multiple curettages.
2. Previous C-sections.
3. Severe endometritis.
4. Closely spaced pregnancies.
Severe preeclampsia refers to ...?
The SUDDEN development of :
1. MATERNAL HTN (>160/110mmHg).
2. Edema (hands and/or face).
3. Proteinuria (>5g/24hr).
Preeclampsia usually occurs ...?
After week 32 of gestation (3rd trimester).
Eclampsia is ...?
Preeclampsia + Convulsions.
The central pathophysiologic concept behind preeclampsia is ...?
Generalized arteriolar constriction.
BRAIN --> Seizures and stroke.
KIDNEYS --> Oliguria/ARF.
LIVER --> Edema.
SMALL BVs --> DIC + Thrombocytopenia.
Treatment of severe preeclampsia:
1. Mg sulfate --> Seizure prophylaxis.
2. Hydralazine --> Blood pressure control.
3. Once the patient is stabilized --> IMMEDIATE delivery of the fetus.
Risk factors for preeclampsia:
4. Renal disease.
5. Twin gestation.
6. Hydatidiform mole.
Hydatidiform mole produces ...?
The placenta as an endocrine organ - 4 hormones:
3. Estrone, estradiol (most potent), and estriol.
hCG is a ...?
Glycoprotein hormone that STIMULATES the production of PROGESTERONE by the corpus luteum.
hPL is a ...?
Protein hormone that induces lipolysis, elevating FFAs in the MOTHER --> Considered to be a GROWTH hormone of the fetus.
Why does the placenta produces progesterone?
1. Maintains endometrium during pregnancy.
2. Used by the FETAL adrenal cortex --> Gluco/mineralocorticoid synthesis.
3. Used by FETAL TESTES --> As a precursor for testosterone synthesis.
In EARLY pregnancy, the placental membrane consists of the ...?
2. Cytotrophoblasts (Langerhans cells).
3. Connective tissue.
4. Endothelium of the fetal capillaries.
5. Hofbauer cells.
Found in the connective tissue --> Most likely MACROPHAGES.
In LATE pregnancy, the changes in the placental membrane are:
1. The cytotrophoblast degenerates.
2. The connective tissue is displaced by the growth of the fetal capillaries.
3. The syncytiotrophoblast + the fetal capillary endothelium remains.
The placental membrane separates ...?
Maternal blood from fetal blood.
Beneficial substances that cross the placenta:
1. O2, CO2.
2. Glucose, L-aminoacids, FFAs, vitamins.
3. H2O, Na, K, Ca, Cl, I, PO4.
4. Urea, uric acid, bilirubin.
5. Fetal and maternal RBCs.
6. Maternal serum proteins, AFP, transferrin-Fe complex, LDL, prolactin.
7. Steroid hormones (unconjugated).
8. IgG, IgA.
Harmful substances that cross the placental membrane:
6. Variola (smallpox).
Substances that do NOT cross the placenta:
1. Maternally derived CH, TGs, and phospholipids.
2. Protein hormones (eg insulin).
3. Some drugs --> Heparin, methyldopa, curare, succinylcholine.
4. IgD, IgE, IgM.
5. Bacteria in general.
Mother Rh(-) + Fetus Rh(+) --> Mother produces Rh antibodies.
--> 2nd pregnancy Fetus Rh(+) --> Hemolysis --> Known as Rh-hemolytic disease of the newborn (Erythroblastosis fetalis).
Hemolytic disease of the newborn --> Large amounts of UNconjugated bilirubin --> Fetal brain damage --> Due to pathological deposition of bilirubin in the basal ganglia.
Severe hemolytic disease, in which the fetus is severely anemic + demonstrates total body edema --> May lead to death.
Hydrops fetalis requires ...?
Prevention of erythroblastosis fetalis?
Rh(D) Ig (RhoGAM, MICRhoGAM) --> Human IgG preparation that contains antibodies against Rh factor + prevents a maternal antibody response to Rh(+) cells that may enter the maternal bloodstream of an Rh(-) mother.
When do we give the Rh(D) Ig in order to prevent erythroblastosis fetalis?
During the 3rd trimester + within 72hr after the birth of an Rh(+) baby to prevent erythroblastosis fetalis during SUBSEQUENT pregnancies.
Amniotic fluid is a ...?
Maternally derived water that contains:
5. Proteins (hormones, enzymes, AFP).
10. Desquamative fetal cells.
11. Fetal urine.
12. Fetal feces (meconium).
13. Fetal lung liquid (useful for lecithin/sphingomyelin (L/S) ration measurement for lung maturity).
Amniotic fluid is constantly produced during pregnancy by the following:
1. Direct transfer from maternal circulation in response to osmotic and hydrostatic forces.
2. Excretion of fetal urine by the kidneys into the amniotic sac.
Kidney defects (eg bilateral kidney agenesis) result in ...?
Amniotic fluid is constantly resorbed during pregnancy by the following sequence of events:
1. The fetus shallows amniotic fluid.
2. Amniotic fluid is absorbed into fetal blood through the GI tract.
3. Excess amniotic fluid is removed via the placenta and passed into maternal blood.
Shallowing defects (esophageal atresia) or absorption defects (duodenal atresia) result in ...?
The amount of amniotic fluid is ...?
Gradually INCREASING during pregnancy --> 50mL at week 12 to 1L at term.
The rate of water exchange within the amniotic sac at term is ...?
400-500mL/h. (net flow of 125-200mL/h moving from the AF into the maternal blood.
The near-term fetus excretes about ...mL of urine daily, which is mostly water because the placenta exchanges metabolic wastes.
The fetus shallows about ...mL of AF daily.
Oligohydramnios occurs when there is a low AMOUNT of AF (
Oligohydramnios result in many fetal deformities including ...?
Potter syndrome + Hypoplastic lungs due to increased pressure on the fetal thorax.
Polyhydramnios occurs when there is a high amount of AF (>...mL in LATE pregnancy).
Polyhydramnios may be associated with the inability of the fetus to shallow due to ...?
2. Esophageal atresia.
3. Duodenal atresia.
Polyhydramnios is commonly associated with ...?
AFP is ...?
"Fetal albumin" that is produced by FETAL HEPATOCYTES.
AFP is routinely assayed in amniotic fluid + maternal serum between weeks ... and ... of gestation.
AFP levels change with ...?
Gestational age --> Proper interpretation of AFP levels is dependent on an accurate gestational age.
Elevated AFP levels may be associated with:
1. Neural tube defects (spina bifida or anencephaly).
2. Omphalocele (allows fetal serum to leak into the amniotic fluid).
3. Esophageal + duodenal atresia (which interfere with fetal shallowing).
Decreased AFP levels are associated with ...?
MCC of premature labor + oligohydramnios?
Premature rupture of the amniochorionic membrane --> Commonly referred to as "breaking of the water bag".
What happens in amniotic band syndrome?
Occurs when bands of amniotic membrane encircle + constrict parts of the fetus --> Limb amputations + craniofacial anomalies.
Umbilical cord - Primitive umbilical ring?
A patent OPENING on the VENTRAL surface of the developing embryo through which 3 structures pass.
Which 3 structures pass through the primitive umbilical ring?
1. The yolk sac (vitelline duct).
2. Connecting stalk.
Fate of allantois in humans?
NOT FUNCTIONAL in humans - Degenerates to form the MEDIAN UMBILICAL LIGAMENT in the adult.
As the amnion expands...?
It pushes the vitelline duct + connecting stalk + allantoid together to form the PRIMITIVE UMBILICAL CORD.
Gross morphology of the definitive umbilical cord?
2. 1-2cm diameter.
3. 50-60cm long.
4. Eccentrically positioned.
5. Contains R+L umbilical ARTERIES + L umbilical VEIN + Mucus connective tissue (Wharton's jelly).
Role of the R+L umbilical arteries?
Carry DEOXYGENATED blood from the fetus to the placenta.
Role of LEFT umbilical vein?
Carries oxygenated blood from the placenta to the fetus.
Umbilical cord - Clinical considerations - Presence of one umbilical artery:
Presence of 1 umbilical artery within the umbilical cord is an abnormal finding that suggests CARDIOVASCULAR abnormalities.
--> Normally, 2 umbilical arteries are present.
Umbilical cord - Clinical considerations - Physical inspection of the umbillicus may reveal:
1. A light-gray, shiny sac indicating an omphalocele.
2. A fecal (meconium) discharge indicating a vitelline fistula.
3. A urine discharge indicating an URACHAL fistula.
Vasculogenesis is ...?
De novo blood vessel formation.
The 2 locations in which the vasculogenesis occurs?
1. In extraembryonic mesoderm.
2. In intraembryonic mesoderm.
Where does vasculogenesis occur first?
Within extraembryonic visceral mesoderm around the yolk sac on day 17.
Vasculogenesis - By day 21 ...?
By day 21, vasculogenesis extends into extraembryonic SOMATIC MESODERM located around the connecting stalk to form the UMBILICAL VESSELS and in secondary villi to form TERTIARY CHORIONIC VILLI.
Process of vasculogenesis:
Vasculogenesis occurs by a process in which EXTRAEMBRYONIC mesoderm differentiates into ANGIOBLASTS --> Form clusters known as ANGIOGENIC cell clusters.
The angioblasts located at the periphery of angiogenic cell clusters give rise to ...?
Endothelial cells - Which fuse with each other to form SMALL BLOOD VESSELS.
Mechanism of vasculogenesis in intraembryonic mesoderm?
Blood vessels form within the embryo by the SAME mechanism as in extraembryonic mesoderm.
What happens eventually, during progression of extraembryonic and intraembryonic vasculogenesis?
The BVs formed in the extraembryonic mesoderm become continuous with BVs formed within the embryo --> Thereby establishing a blood vascular system between the embryo and the placenta.
Hematopoiesis - First occur when?
Within the extraembryonic VISCERAL mesoderm around the yolk sac during week 3 of development.
What happens in the beginning of the hematopoietic process?
Angioblasts within the center of angiogenic cell clusters give rise to PRIMITIVE blood cells.
Beginning at week 5, hematopoiesis is taken over by a sequence of embryonic organs:
4. Bone marrow.
During the period of yolk sac hematopoiesis, the EARLIEST embryonic form of Hb is ...?
During the period of liver hematopoiesis, which form of Hb predominates?
The FETAL form - HbF.
Why is it essential for the HbF to be the predominate Hb form during pregnancy?
Due to higher affinity for O2 --> "Pulls" O2 from maternal blood into fetal blood.
Period of bone marrow hematopoiesis?
About WEEK 30.
How does hydroxyurea promote HbF production?
By the reactivation of γ-chain synthesis.
Hydroxyurea has been especially useful in the treatment of ...?
Beginning of hematopoiesis by the liver?
Beginning of hematopoiesis by the thymus/spleen?
Fetal circulation involves 3 shunts?
1. The ductus venosus.
2. Ductus arteriosus.
3. Foramen ovale.