Maternal Fetal Circulation

Question 1

Fxns of the placenta

Answer 1

• Metabolism: synthesizes glycogen
• Transports gases & nutrients
• Endocrine: hCG
• Excretion of fetal waste products

Question 2

Anatomic structure of placenta- two plates

Answer 2

• Maternal part: formed by decidua basalis (endometrium of uterus at implantation site)
  
  • Basal plate
• Fetal part is formed by the villous chorion
  
  • Chorionic plate: where the umbilical veins and artery branch from the umbilical cord into stem villi

Grossly, the placenta is organized into cotyledons, eacho which consists of multiple stem villi

Question 3

Anatomic structure of chorion

Answer 3

Chorion: the outermost fetal membrane; covered in vascular processes called primary chorionic villi

• Syncytiotrophoblast
• Cytotrophoblast
• Extraembryonic mesoderm

Question 4

Structure of amnion (3 stages)

Answer 4

Amnion:

1. Membrane that is part of developing embryo at first
2. Fills with fluid to become a sac that envelops the embryo.
3. Then it merges with the chorion to create the amniochorionic membrane that ruptures during birth.

Question 5

decidua

Answer 5

Decidua: functional endothelial layer of the uterus in a pregnant woman; secretes glycogen and accumulates lipid (fat) to a rich source of nutrition for the embryo

Question 6

Structure of placental membrane

Answer 6

Placental membrane: the “barrier” between maternal and fetalcirculation

• Syncytiotrophoblast
• Cytotrophoblast
• Connective tissue of villi from mesenchyme
• Endothelium of fetal capillaries

Question 7

Physiological funcitoning of placental membrane

Question 8

Structure of a primary chorionic villi

Answer 8

Cytotrophoblastic core, syncytiotrophoblast covering.

Then, mesenchyme invades and becomes capillaries and blood vessels.

Question 9

Structure of decidua

Answer 9

• Decidua basalis: endometrium deep to the conceptus; will form maternal membrane
• Decidua capsularis: endometrium overlying the developing conceptus
• Decidua parietalis: rest of endometrium; isn’t the implantation site or the opposing site of conceptus

Question 10

4 transport mechanisms that allow substances to cross the placental membrane

Answer 10

• Simple diffusion: freely exchangeable across the membrane
  
  • Gases
• Facilitated diffusion: transport via an electrical gradient or carrier
  
  • Glucose
• Active transport: use energy
  
  • Ions & molecules
• Pinocytosis: engulf substrate being crossed
  
  • Large molecules

Question 11

Preeclampsia

Answer 11

• Generalized arteriolar constriction –>
  
  • Maternal hypertension +
  • Proteinuria
  • Edema
• Can lead to eeclampsia (one or more convulsions) that may result in miscarriage and maternal death.
  
  • Causes placental infarcts (blockage of blood to organ) –> reduced fetal blood supply
  • Impacts brain, kidneys, liver,

Question 12

Gestational choriocarcinoma

Answer 12

Gestational choriocarcinoma: abnormal proliferation of trophoblast results in highly malignant tumors.

• Tumors invade decidua basalis, penetrating blood vessels and lymphatics –>metastasize to maternal lungs, bone marrow, liver, and othe rorgans
• Chemotherapy

Question 13

Placental abnormalities with clinical implications - placenta accreta

Answer 13

Abnormal adherence of the chorionic villi to the myometrium

Question 14

Placental abnormalities with clinical implications - placenta percreta

Answer 14

Chorionic villi penetrate the full thickness of the myometrium

Question 15

Placental abnormalities with clinical implications - placenta previa

Answer 15

Placenta implants close to or overlying the internal os of the uterus

Question 16

Stages of Labor and the birth process

Question 17

Functions of amniotic fluid

Answer 17

• Permits symmetric external growth of the embryo/fetus
• Barrier to infection
• Permits fetal lung development
• Prevents amnion adhering to the embryo/fetus
• Cushions embryo/fetus
• Helps control temp
• Enables the fetus to move freely –> muscular development
• Helps maintain fluids/electrolytes homeostasis

Question 18

Oligohydramnios

Answer 18

• Too little amniotic fluid.
• Cause: diminished placental blood flow or occasionally premature rupture of membranes or renal agenesis.
• Clinical implications:
  
  • If the cause is ruptured membrane, then fetus is at risk of infection.
  • If severe, then respiratory, facil, and limb defects are possible.

Question 19

Polyhydramnios

Answer 19

• Excessive amniotic fluid.
• Cause: Usually unknown, but can be caused by CNS defects
• Implications: May not have complications, but may indicate birth defects.

Question 20

Amniotic band syndrome

Answer 20

Amniotic band syndrome

• Separations of the amnion that cling ot and constrict the fetus
• Cause: tearing of amnion o rvascular disruption of growing fetus
• Implications: birth defects

Question 21

Twin transfusion syndrome

occurs in what types of twins?

What happens?

Which twin dies and which gets congestive heart failure?

Answer 21

Twin transfusion syndrome

• Occurs in ~10% of monochorionic-diamniotic in monozygotic twins
• Arterial blood is shunted from one twin through arteriovenosus anastomoses into venous circulation of the other twin.
  
  • Donor = small, pale, anemic –> may die
  • Recipient = large, polycythemia (increased RBCs) –> may have congestive heart failur

Question 22

Anastomoses between blood vessels of fused placentas in dizygotic twins may result in

Answer 22

Erythrocyte mosaicism: the individual has RBCs of two differen tblood groups

Question 23

Embryonic age vs Menstrual/gestational age

Answer 23

Embryonic age: age of actual embryo

Menstrual/gestational age: estimating the age of the fetus by knowing the woman’s last menstrual cycle because women usually ovulate 2 wks after that date. Thus, the embryo is probably 2 wks younger than that age.

Ex) A 4 wk old embryo that is folding is 6 wks in menstrual age.