Physiology of Fetus and Placenta

Question 1

Three fetal ducts that maximize blood flow to fetus brain and coronary arteries and circulation

Answer 1

Placenta –> umbilical vein (most oxygenated) –> shunted past liver via ductus venosus –> IVC –> right atrium (some mixing of blood) –> 1, new blood from IVC: foramen ovale –> left atrium –> left ventricle –> aorta –> brain and 2, deox blood from brain: right ventricle –> pulmonary artery –> ductus arteriosius –>descending aorta –> umbilical arteries –> placenta

Question 2

Which fetal vessel has the most oxygenated blood for fetus

Answer 2

umbilical vein

Question 3

Which fetal vessels take blood to the placenta

Answer 3

umbilical arteries

Question 4

Where in the fetal heart is blood mixed?

Answer 4

right atrium –> return blood from brain and higher oxygen “fresh” blood from IVC –> some mixing but currents ensure most brain blood gets to right ventricle and most fresh blood gets to left atrium

Question 5

When baby is born and cord is clamped ____ regresses

Answer 5

ductus venosus

Question 6

When baby is born and takes first breath ____ dilate and ____ constricts.

Answer 6

vessels going to lung dilate and ductus arteriosus constricts

Question 7

How does fetus avoid rejection by mother

Answer 7

HLA-G is not recognized by nonself MHC I and protects against NK cell attack

Question 8

_____ is the primary site of placental hormone production

Answer 8

syncytiotrophoblast

Question 9

HCG

Answer 9

single alpha subunit common to LH/FSH/TSH –> chr6; cluster of 7 beta units, chr19

Question 10

T/F women in early pregnancy can be hyperthyroid

Answer 10

T –> because of shared alpha subunit with HCG

Question 11

When can hCG be detected in maternal serum?

Answer 11

8 days after ovulation

Question 12

After implantation, _______ produce most of the fetal hCG

Answer 12

villous syncytiotrophoblast

Question 13

maternal serum levels of hcg _____ every 1.4 days during pregnancy

Answer 13

double –> peak at 10 weeks and the ndecline

Question 14

Roles of hCG

Answer 14

maintain corpus luteum –> LH/CG receptor activates adenylyl cyclase and steroidogeneis; binds to TSH receptors

Question 15

T/F antisera to hCG in early gestation causes pregnancy termination

Answer 15

T

Question 16

____ test helps distinguish between intrauterine and ectopic pregnancy

Answer 16

hCG doubling time + ultrasound

Question 17

MMS: multiple marker screening

Answer 17

bunch of fetal proteins that can be screened that indicate potential genetic issues

Question 18

T/F fetal and placental compartments must work together to make estrogen because each are missing one enzyme.

Answer 18

T

Question 19

Fetal adrenal makes ___ which goes to the placenta to be made into _____

Answer 19

dhea and estradiol

Question 20

T/F fetus never makes cortisol

Answer 20

T –> no negative feedback to fetal pituitary so always pumping out DHEA

Question 21

Placenta is the major source of _____

Answer 21

progesterone

Question 22

2 roles of progesterone

Answer 22

during luteal phase, prepares endometrium for implanation, and prevents maternal immune rejection of trophoblast (because inhibits hte production of cytolytic cytokines)

Question 23

T/F progesterone is a smooth muscle relaxant

Answer 23

prevents gap junction formation in muscle, reduces calcium channel synthesis, and decreases oxytocin receptors –> reduces muscle tone –> side effects = heartburn, urine stasis/utis, etc

Question 24

____ estrogen is almost exclusively derived from fetal adrenal while ____ estrogen is equivalently derived from maternal and fetal systems

Answer 24

estriol vs estradiol

Question 25

2 zones of fetal adrenal cortex

Answer 25

thick inner fetal and thin outer definitive zones

Question 26

Thick inner fetal zones

Answer 26

> 80% of the bulk of the gland, rapidly involutes after delivery, produces lots of DHEA, minimal production of cortisol

Question 27

______ stimulates fetal adrenal to conduct steroidgenesis

Answer 27

ACTH –> not inhibited because of low fetal cortisol + placental deactivation of maternal cortisol

Question 28

Actions of estrogens

Answer 28

fetal control of maternal physiology, vasodilation of spiral arteries, parturition (placental CRH, myometrial gap junctions, mammary epithelial proliferation)