Placenta and Fetal Membranes Flashcards
In week 1, the formation of ___ gives rise to the embryo.
Inner Cell Mass
In week 2, formation of ____ gives rise to the placenta.
Trophoblast
What is the stem cell layer of week 1? What else is special about it?
Cytotrophoblast, mitotically active
What layer of the trophoblast releases hCG?
Syncytiotrophoblast
What does hCG signal?
Initial signal of pregnancy
What occurs on day 6 of fertilization?
Syncytiotrophoblast has released proteolytic enzymes for embryo to start to implant
Formation of the bilaminar disc occurs in what week?
Week 2
What layer of the bilaminar disc does the amnion and amniotic cavity derive from?
Epiblast
What does the decidua reaction occur in response to?
Syncytiotrophoblast burrowing into the endometrial lining
What occurs during the decidua reaction?
Endometrial changes to provide glycogen and nutrients as well as an immunologically privileged site for embryo (prevent rejection)
What does the extraembryonic somatic mesoderm line?
Trophoblast and covers amnion
What does the extraembryonic splanchnic mesoderm line?
Yolk sac/umbilical vesicle
What is the connecting stalk derived from?
Extraembryonic somatic mesoderm
What does the hypoblast give rise to?
Primary and secondary yolk sac
What are the three layers of the chorion?
Extraembryonic somatic mesoderm
Cytotrophoblast
Syncytiotrophoblast
What is produced in excessive amounts in a hydatidiform mole?
Abnormal trophoblastic proliferation => excess hCG
What does a complete hydatidiform mole result from?
Fertilization of empty oocyte by 1 sperm that duplicates or by 2 separate sperm => 46 chromosomes, all paternal
What does a partial hydatidiform mole result from?
Fertilization of normal oocyte by 2 sperm => 69 chromosomes, part mom part dad
What is the big symptom of a hydatidiform mole?
Hyperemesis gravidarum (morning sickness) from the excess hCG
(also present with vaginal bleeding, pelvic pain, enlarged uterus)
If a hydatidiform mole becomes malignant, what can result?
A choriocarcinoma - malignant
What makes up the fetal part of the placenta?
Chorionic sac
Amnion
What makes up the maternal part of the placenta?
Decidual basalis
Decidua Capsularis
What are the 3 sources of amniotic fluid?
Amnion
Fetal urine
Maternal circulation
What is the composition of amniotic fluid?
Ions and small molecules
Glycophospholipids
Steroids
Particulates/cells from embryo
What are the functions of the amniotic fluid?
Cushions against injury
Maintains temperature
Ease of movement
Diagnostic information
Renal agenesis in the developing embryo can cause what to happen during pregnancy?
Oligohydramnios (no kidneys to produce fetal urine)
What are the common causes of oligohydramnios?
Renal agenesis
Placental insufficiency
Premature rupture of membranes
Polyhydramnios during pregnancy can result from failure of what?
Fetal swallowing
What are the common causes of polyhydramnios?
Anencephaly
Esophageal atresia
Maternal diabetes
Multifetal gestations
Hypoplastic lungs (can be for both oligo and poly)
What occurs during amniotic band syndrome?
Portions of amnion are sloughed off and wrap around extremities to cause amputation
What is an exogenous cause of amniotic band syndrome?
Trauma to amnion => delamination
What is an endogenous cause of amniotic band syndrome?
Poor vascular supply causes necrosis of amnion => delamination
When are primary chorionic villi formed?
Days 13-14
When are secondary chorionic villi formed?
Day 15-18
What is the difference between a primary and secondary chorionic villus?
Secondary have all 3 layers (Extraembryonic mesoderm, cytotrophoblast, and syncytiotrophoblast), primary only has trophoblastic layers
What does the trophoblast lacuna give rise to?
Intervillous space filled with maternal blood
What is the significance of the cytotrophoblastic shell?
Serves as interface between mom and fetus
When are tertiary chorionic villi formed?
Days 19-21 (End of week 3)
What does the extraembryonic mesoderm give rise to in a tertiary chorionic villus?
Villous capillaries
What do the stem/anchoring villi connect to in the intervillous space?
Cytotrophoblastic shell (at the apex of the villus, towards maternal side)
What is the purpose of the chorionic villi?
Nutrient and gas exchange between mother and fetus
In what week does the chorionic villi cover the chorionic sac?
Week 8
Where is the decidua basalis in the endometrium?
Deep to the conceptus (embryo)
Where is the decidua capsularis in the endometrium?
Superficial part of decidua overlying conceptus (its coat)
Where is the decidua parietalis in the endometrium?
Walls of uterus, everywhere that is not part of the basalis and capsularis
What is the smooth chorion formed from?
Decidua capsularis that has been flattened by the growing embryo
After formation of the smooth chorion, what is the fate of the decidua capsularis?
Fuses with the decidua parietalis and degenerates from lack of blood supply
After degeneration of the decidua capsularis, what is the fate of the smooth chorion?
Fuses with decidua parietalis
After fusion of the smooth chorion with the decidua basalis, what space is obliterated?
Uterine cavity (now filled with embryo)
What is the dividing line between early placental layers and late placental layers?
Week 20
What placental layers must gas and nutrients travel through prior to week 20?
Syncytiotrophoblast
Cytotrophoblast
Villi connective tissue
Endothelium of fetal capillaries
What are the placental layers gas and nutrients must travel through after week 20?
Syncytiotrophoblast
Vasculosyncytial basement membrane
Endothelium of fetal capillaries
DC: Decidual cells
DB: Decidual Basalis
AV: Anchoring chorionic villi
IS: Intervillous space
N: Nuclei
TV: Terminal Villi
Me: Mesoderm
ST: Syncytial trophoblasts
TV: Terminal Villi
SK: Syncytial Knots
Ca: Capillaries
IS: Intervillous space
When was this slide taken? What are the numbers labelled?
Midterm placenta
10: Intervillous space
11: Syncytiotrophoblast
12: Trophoblastic bud
13: Cytotrophoblast
14: Hofbauer cells
When was this slide taken? What are the labelled numbers?
3rd week - secondary villus
7: Mesodermal core
8: Cytotrophoblast cells
9: Syncytiotrophoblast
When was this slide taken? What is labelled?
Full term placenta
1: Chorionic villi
2: Intervillous space
3: Umbilical V.
4: Syncytiotrophoblast
5: Cytotrophoblast (remnant cells)
6: Placental macrophages (Hofbauer cells)
What are Hofbauer cells and where are they found?
Placental macrophages
Found in the terminal/branching villi, found between syncytiotrophoblast and cytotrophoblast
What are cotyledon?
Main stem villi and all branches that appear as lobules on the maternal side of the placenta
What is this? What is labelled?
Amniotic placental surface
A: Amnion
CP: Chorionic plate
CV: Chorionic villi
What is this? What is labelled?
Maternal placental surface
DC: Decidual cells, only if decidua basalis present (not on the amniotic side)
What is placenta accreta?
Abnormal adherence of chorionic villi to myometrium
What is Placenta Increta?
Chorionic villi penetrate into the myometrium
More severe than placenta
What is placenta percreta?
Chorionic villi penetrate through the myometrium to uterine serosa or adjacent organs
Most severe - placenta will not release during childbirth => hemorrhage
What is the typical treatment for placenta percreta?
Hysterectomy, partial removal of uterus
How does placenta previa prevent?
Vaginal bleeding beyond 20 weeks gestation
How should antepartum bleeding be evaluated?
Ultrasound BEFORE digital vaginal exam (can cause hemorrhage)
What can cross the placenta?
Nutrients (water, clucose, AAs, vitamins)
Hormones (steroid and thyroid hormones)
Ab (IgG, urea/uric acid, conjugated bilirubin)
Most drugs
Infectious agents (viruses)
What cannot cross the placenta?
Protein hormones (insulin, pituitary hormone)
Ab (IgD, IgM, IgA, IgE)
Heparin
Bacteria
How does hemolytic disease of the newborn develop?
Rh+ father and Rh- mother have a child => Rh+ baby’s blood enters mother’s bloodstream => mother develops Ab for the Rh+ baby => Rh Ab attack baby’s blood cells (Baby 2, not baby 1)
Which maternal Ab are attacking the Rh+ fetus?
IgG
What is a mild presentation of hemolytic disease of the newborn?
Hyperbilirubinemia in first 24 hours of life
Symptomatic anemia (lethargy or tachycardia) but without signs of circulatory collapse
What is a severe presentation of hemolytic disease of the newborn?
Hydrops fetalis
Skin edema
Pleural or pericardial effusion
Ascites
What layer does the allantois arise from?
Endoderm
What is the function of the allantois?
Provide template for umbilical arteries and vein
Becomes urachus
What makes up the core of the umbilical cord?
Extraembryonic mesoderm
How many arteries/veins in the umbilical cord?
2 Umbilical As.
1 Umbilical V.
What is the outer covering of the umbilical cord?
Amnion
What travels through the umbilical cord?
2x Umbilical As.
Umbilical V.
Allantois
Vitello-intestinal duct
Extraembryonic coelom
What is a consequence of a true umbilical knot?
Prevents blood flow to the fetus => fatal
What is the clinical significance of an absent umbilical A.?
15-20% incidence of CV defects
Chromosoma/fetal abnormalities
In MZ twins, if the fertilized egg split at Day 2, what layers surround the resulting twins? How frequently does this occur?
2x amnion
2x Chorion
2x Placenta
25% of cases
In MZ twins, if the fertilized egg split at 4 days, what are the layers surrounding the twins? How frequently does this occur?
2x Amnion
1 Chorion
1 Placenta
75% of cases
In MZ twins, if the fertilized egg split in week 2, what are the layers surrounding the twins?
1 amnion
1 chorion
1 placenta
When is the embryo thought to have split in the case of conjoined twins?
In week 3, after formation of the primitive streak
