Lecture 35: Physiology of Fetus and Placenta Flashcards
Where does the fetus develop from?
The inner cell mass
What part of the placenta is closest to fetus?
Amnion
What part of placenta is closest to mother?
Decidua basalis
What part of placenta is in the middle?
Chorion
How many cells are the fetal blood and the maternal blood separated by?
2 cells in width
What are the three adaptations that allow fetal circulation to take place in placenta than lungs?
- ductus venosus (takes blood away from liver)
- foramen ovale
- ductus arteriosus (shutns blood from right ventricle and pulmonary artery to descending aorta
What are the two characteristics of placental blood exchange?
Increased blood flow from mom the fetus
Surface exchange rate (the idea is to get mothers blood closer to baby’s blood to increase this rate)
What is the umbilical vein of fetus?
PO2 = 30%
This is the most oxygenated part of the circulation of fetus
When is hCG detected? What happens if you have abnormal hCG doubling?
8 days
Abnormal doubling = ectopic pregnancy
What are the 3 adaptations the baby ahs to counter the low PO2?
- fetal hemoglobin
- fetal heart pumps fast
- ductus venosus, foramen ovale, ductus arteriosus
- shunts that make sure the blood stays oxygenated
What are the functions of placenta?
- hormone production
- nutrient transport
- Prevents immune rejection
- HLA-G
- waste excretion
What is the primary site of hormone production in placenta?
Syncytiotrophoblast
Hormones released into maternal circulation
Estrogen and progesterone
What is the purpose of the hCG?
- maintain the corpus luteum
-LH/CG receptor
-activation of adenylyl cyclase
-steroidogenesis - antisera to hCG in early gestation causes pregnancy termination
- binds to TSH receptors
Creates a “favorable environment” which means we don’t know shit
What is CVS?
Chorion villus sampling
What is the HIV transmission rate of woman to baby?
25%
That’s astounding!
What is the physiologic role of progesterone in pregnancy?
- maintains endometrium and endometrial blood supply
2. inhibits myometrial contraction (along with relaxin)
What is the importance of the fetal adrenal gland?
Fetal adrenal gland must work TOGETHER with placenta to make estrogen
What does placenta lack? Can make what?
P450c17
Makes progesterone and gets stuck
What does fetal adrenal gland make? What does it lack?
It makes DHEA
Lacks 3beta HSDII
How does placent and fetal adrenal glands work together to make estradiol?
DHEA in fetal adrenal glands gets transported to placenta
Placenta has 3beta HSDII which allows the DHEA to be converted to estradiol!!
What is the role of ACTH in fetal development?
It signals fetal adrenal gland to produce DHEA
What happens when you have anencephaly in the fetus?
No ACTH so no DHEA being made
That means adrenal atrophy after 20 weeks
What is the significance of fetal adrenal cortex LACKING 3bHSDII?
It means that pregnenolone cannot be converted to cortisol
This means that there is no negative feedback and you can continue to form DHEA which gets converted to estradiol in placenta
What do you measure to gauge fetal placental estrogen production?
Estriol (E3)
90% of estriol in mother’s body is from fetus
