Physiology of Pregnancy and the Fetus Flashcards
What is the main function of the placenta?
acts as fetal gut, lung and kidney to supply nutrients, exchange gases and regulate fluid/waste levels
functions as an endocrine gland to synthesize steroids and proteins that affect both maternal and fetal metabolism
What is the interface to facilitate exchange between maternal and fetal circulations?
The placenta
it has a large surface area and is very vascular for the fetus and the mother
What are the three major features of the placenta?
Chorionic villi
Intervillous space
Decidua basalis
What is the functional unit of the placenta?
the chorionic villi are the functional unit of the placenta with extensive branching and increased surface area for exchange
Describe maternal blood flow
arterial blood is discharged from spiral arteries into intervillous space
intervillous spaces dissipates the force and reduces blood velocity
slowing the blood down allows for gas exchange
blood is drained through the venous orifaces and enters placental veins
NO CAPILLARIES
Describe fetal blood flow
- originates from the two umbilical arteries and carried DEOxygenated blood throught the chorionic placte to make the chorionic villi capillary networkd
- obtains O2 and nutrients and returns to fetus from one umbilical vein
- terminal dilations in capillary network allow slower blood flow and exchange of nutrients
How does gas/solute exchange between mother and fetus occur?
diffusion of O2 into the chorionic villu causes the PO2 of blood in intervillous space to fall to 30-35 mmHg and lower in umbilical vein of the fetus
difference in Hgb structure allows for sufficient Hgb saturation
What is the role of HCG?
- produced by synctiotrophoblasts
- binds to LH recepors and rapidly accumulates in maternal circulation-doubles daily up to 10wks
- primary function is to stimulate LH receptors on Corpus Luteum to prevent luteolysis and maintain progesterone levels
- assx with nausea and can produce testosterone in fetus
What is the role of Human Chorionic Somatomammotropin
- made by synctiotrophoblasts
- role in coordinating fuel economy of fetoplacental unit by converting glucose to FA and ketones
- contributes to GDM
- helps mother shift to free fatty acids for energy (lipolytic)
- promotes developement of maternal mammary glands
What is the role of progesterone in pregnancy?
- required for implantation and early maintanance
- increases adhesive proteins in endometrium
- stimulates endometrial gland secretion for nutrient transfer
- reduces uterine motility
- inhibits uterine contractions
- induces mammary growth/differentiation
What is the role of estrogen in pregnancy?
- induces endometrial growth, progesterone receptor expression, LH surge
- increases ureteroplacental blood flow
- increases LDL receptor expression for synctiotrophoblasts
- induces prostaglandins and oxytocin for labor
- increases growth/dev. of mammary glands
Coordination between maternal tissues, placenta and fetus is necessary because?
maternal levels of estrogen and progesterone increase greater than what the placenta alone is capable of providing
Mother supplies necessary cholesterol (levels are really high in pregnancy compared to not-pregnant)
fetal adrenal gland and lvier supply enzymes that the placenta lacks
Initially the corpus luteum is producing progesterone for the pregnancy, but the placenta takes over at what week?
What does progesterone do in terms of synctiotrophoblats?
Week 8 and is largely unregulated
Imports cholesterol from maternal blood and increases expression of CYP11A1 and 3B HSD1
The placenta cannot produce cholesterol, because it lacks what? Which means it can;t make what?
How is this overcome?
17a hydroxylase and 17, 20 desmolase needed for estrone/estradiol and lacks 16a for estriol
Fetus produces DHEAS which can be converted to estrogen
What is preeclampsia?
- high blood pressure with possible damage to kidneys and other organs
- assx with proteinuria and generalized edema
- can lead to decreased blood flow to uterine arteries, causing ischemia and placenta may be poorly trophoblastic
- Can lead to eclampsia (seizures) and HELLP Syndrome (hemolysis, elevated liver enzymes, low platelet count)
