NM702 MODULE 3: PLACENTATION EXAM ACTUAL QUESTIONS
AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
When does blood flow into the intervillous space begin? Why does this not begin
immediately?
The highly oxygenated maternal blood does not fill the IVS until fetal vessels are
established in the villi and mechanisms to protect the fetus against oxidative stress are
established. This begins at 8 to 9 weeks and increases after 10 to 12 weeks.
How does the oxygen concentration in the intervillous space compare to the oxygen
concentration in the surrounding decidua when the intervillous space forms?
•Oxygen concentration in the IVS at 8 weeks is 20 mmHg (3% to 5% O2) versus 60
mmHg (8% to 10% O2) in the surrounding decidua.
Does initial placental and embryonic development occur in an oxygen-rich environment
or a hypoxic environment? Why?
•Thus initial placental and embryonic development occurs in a relatively hypoxic
environment. This environment may stimulate production of vascular endothelial growth
factor and stimulate chorionic vascularization. Low O2 levels may be essential for
control of early cardiovascular development by hypoxia inducible factors (HIF).
What is the role of hypoxia-inducible factors in development of the placenta? Which
illness that appears later in pregnancy is associated with alteration in HIFs?
, •HIFs act as mediators to allow cells to adjust to low O2 conditions and facilitate
placental vascularization and signaling for trophoblast differentiation.
•Alterations are seen in the pathophysiology of preeclampsia
At what gestation do the spiral arteries become patent, maternal blood flow into the
intervillous space increase, and fetal oxygen levels rise?
•By 11 to 12 weeks the spiral arteries become patent and maternal blood flow into the
IVS and fetal oxygen levels increase.
What are the two layers of the placenta and what do they derive from?
•The placenta consists of the outer epithelial layer, derived from trophoblast cells, and
an inner vascular network and connective tissue stroma, derived from embryonic
mesoderm.
When do chorionic villi begin to appear?
•Chorionic villi begin to appear toward the end of the second week of gestation as
proliferation of the cytotrophoblast layer produces columns of cells or fingerlike
processes known as primary chorionic villi.
What 3 things stimulate villous development?
•Villous development is stimulated by growth factors such as vascular endothelium
growth factor (VEGF) and placental-like growth factor and by the relatively hypoxic
environment.
At how many weeks of gestation is the first fetoplacental circulation established
between the villi and embryo?
AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
When does blood flow into the intervillous space begin? Why does this not begin
immediately?
The highly oxygenated maternal blood does not fill the IVS until fetal vessels are
established in the villi and mechanisms to protect the fetus against oxidative stress are
established. This begins at 8 to 9 weeks and increases after 10 to 12 weeks.
How does the oxygen concentration in the intervillous space compare to the oxygen
concentration in the surrounding decidua when the intervillous space forms?
•Oxygen concentration in the IVS at 8 weeks is 20 mmHg (3% to 5% O2) versus 60
mmHg (8% to 10% O2) in the surrounding decidua.
Does initial placental and embryonic development occur in an oxygen-rich environment
or a hypoxic environment? Why?
•Thus initial placental and embryonic development occurs in a relatively hypoxic
environment. This environment may stimulate production of vascular endothelial growth
factor and stimulate chorionic vascularization. Low O2 levels may be essential for
control of early cardiovascular development by hypoxia inducible factors (HIF).
What is the role of hypoxia-inducible factors in development of the placenta? Which
illness that appears later in pregnancy is associated with alteration in HIFs?
, •HIFs act as mediators to allow cells to adjust to low O2 conditions and facilitate
placental vascularization and signaling for trophoblast differentiation.
•Alterations are seen in the pathophysiology of preeclampsia
At what gestation do the spiral arteries become patent, maternal blood flow into the
intervillous space increase, and fetal oxygen levels rise?
•By 11 to 12 weeks the spiral arteries become patent and maternal blood flow into the
IVS and fetal oxygen levels increase.
What are the two layers of the placenta and what do they derive from?
•The placenta consists of the outer epithelial layer, derived from trophoblast cells, and
an inner vascular network and connective tissue stroma, derived from embryonic
mesoderm.
When do chorionic villi begin to appear?
•Chorionic villi begin to appear toward the end of the second week of gestation as
proliferation of the cytotrophoblast layer produces columns of cells or fingerlike
processes known as primary chorionic villi.
What 3 things stimulate villous development?
•Villous development is stimulated by growth factors such as vascular endothelium
growth factor (VEGF) and placental-like growth factor and by the relatively hypoxic
environment.
At how many weeks of gestation is the first fetoplacental circulation established
between the villi and embryo?
