4.2 Placental metabolism, Pregnancy - Part 1 Flashcards
- what is the placenta?
- comes from which word?
- functions? (6)
- large endocrine organ that develops in the uterus within the first several weeks of conception
- PANCAKE! bc flat lol
1. endocrine function: secreting vital hormones and neurohormones needed to growth and neurodevelopment + hormone catabolism
2. fights infections by passing immunoglobulin G (IgG) antibodies to the fetus
3. transport: exchanges nutrients and oxygen from mother to fetus + removing waste products from fetus to the mother’s blood supply
4. metabolism: synthesis of glycogen, lactate, cholesterol
5. nutrient storage
6. protection against xenobiotics: acting as barrier to harmful substances (only large molecules though, placenta not really a good barrier bc drugs, CO, viruses, toxins can pass)
- what is the amniotic sac/fluid made of?
- functions? (3)
- can be used to determine what?
- the fetus’ urine
- keeps baby safe from drying out + shock protection + allows movement
- to determine risks later on for pregnancy
is there an exchange of blood supply between mother and fetus? explain how exchanges are made
- what is the fetal portion of the placenta called?
no! mother’s arteries and veins –> pool of mother’s blood –> placental villi (to increase surface area) where umbilical/fetus’ arteries and vein are behind ish
- chorion
do all nutrients from mother go towards the fetus?
no! 50% O2 + 65% glucose used by placenta to do its function! vs rest goes to actual fetus
what are the 4 types of transport mechanism across placenta? + which substances are transported
- PASSIVE DIFFUSION:
- O2, CO2
- some FA
- steroids
- electrolytes
- fat soluble vitamins - FACILITATED DIFFUSION:
- sugars
- long chain PUFA (arachidonic acid, eicosanoids, omega3/6) - ACTIVE TRANSPORT:
- amino acids
- cations (Ca, Fe, I, PO4) - SOLVENT DRAG (osmotic pressure):
- electrolytes
what is special about the carriers for sugars and long chain PUFA?
- which type of transport?
facilitated diffusion!
1. sugar
- carriers can be saturated = protective (ie from mother’s high blood glucose)
- bc high levels of glucose in embryo is teratogenic (bc of glycation)
2. long chain PUFA:
- carriers allow them to go only 1 direction (from mother to fetus)
- allows desequilibrium –> good bc need fats for brain development of fetus –> allows for greater bioaccumulation
what are the 4 hormones produced by placenta? + extra
- human chorionic gonadotropin
- human chorionic somatomammotropin (placental lactogen):
- progesterone
- estrogen
*leptin: regulates appetite + mobilizes fat stores + assists with nutrient transportation
describe hcg and human placental lactogen:
-secreted by what, when?
- functions
- human chorionic gonadotropin:
- maintains corpus luteum which secretes estrogen and progesterone
- stimulates growth of endometrium
- secreted by blastocyst by day 7 –> after implantation, produced by placenta, peaks btw 10th and 11th week - human chorionic somatomammotropin (placental lactogen):
- produced in late gestation
- influences fat and CHO metabolism
- increases insulin resistance in mother
- breaks down maternal fats for fuel
describe progesterone and estrogen:
-secreted by what, when?
- functions
- progesterone:
- produced by corpus luteum until 10 weeks –> then placenta takes over
- inhibits secretion of pituitary gonadotropins (LH and FSH) to prevent ovulation and supports endometrium
- suppresses contractility in uterine smooth muscle
- promotes lipid accumulation - estrogen:
- maximal toward end of gestation
- stimulates myometrium growth
- antagonizes myometrial suppression by progesterone
- stimulates mammary gland development
- placenta also does hormone (anabolism/catabolism) explain
- hormone CATABOLISM –> breaks down thyroid and corticosteroids from mother –> if bad health and catabolism is impaired –> thyroids and corticosteroids pass through to fetus –> fetus grows faster but can disrupt its endocrine metabolism = long term consequences
- how is fetal growth compared to placental growth during 3rd trimester
- how to compensate?
Which hormones?
3rd trimester: fetal weight more than doubles (last 10 weeks) but placental weight increases by only 50%
- placental blood flow increases to compensate (stimulated by prostaglandin and leukotriene) –> partially compensates for lower rate of placental growth
consequence of slower placental growth (vs fetal growth) in last 4 wks of gestation?
- progressive decline in qty of nutrients transfers per unit fetal body mass per unit time
- partially responsible for deceleration in fetal growth rate –> mechanisms to increase uterine blood flow to placenta needed
*this is why if prolonged pregnancy, fetus might lose weight
how can maternal malnutrition lead to fetal growth retardation?
5 steps ish
maternal malnutrition –> reduced blood volume expansion (ie from anemia) –> inadequate increase in cardiac output –> decreased placental blood flow –> decreased placental size + reduced nutrient transfer –> fetal growth retardation/intrauterine growth retardation
what (2 ish) can cause placenta to fail?
- what generally causes placenta to fail?
- consequence?
- severe hypotension, renal disease, placental infarction
- Essential FA deficiencies (probs from low cal intake) –> defects in placental integrity and function (bc EFA are needed for local acting hormones + for cell membrane phospholipids)
- often due to failure of uteroplacental blood vessels to deliver increased uterine blood flow
- placental defects can cause intrauterine fetal growth retardation
low levels of (3 nutrients ish) can cause lower placental weight
- linoleic acid
- arachidonic acid
- docosahexaenoic acid (DHA, omega3)
