Placental Metabolism Flashcards
When does the placenta grow the fastest?
1st half of pregnancy
What is exchanged at the placenta?
- nutrients
- respiratory gases
- metabolic waste
- protection of fetus
- sources of hormones
What part of the baby is attached to the placenta?
umbilical cord
How do the babies arteries make their way into the placenta?
they divide into vessels which branch into placental villi
What are4 benefits of amniotic fluid?
- Shock absorber
- prevents desiccation (drying up) of fetus
- provides room for fetal movements
- assists in body temperature regulation
What are cytotrophoblasts?
cells from placenta that connect mother and fetus
What anchors fetal and maternal placenta?
cytotrophoblastic shell & anchoring villi – large area for exchange of material
Deoxygenated blood leaves fetus and enters placenta via what?
umbilical artery
How do the fetus arteries divide in the placenta? Then what do they branch into?
radially (from centre) & branch into chorionic plate, forming vili
Where does the maternal blood flow in the placenta?
in intervillous spaces around the villi
What is the major functioning unit of the placenta?
Chorionic villus
How is the placental villus of intrauterine growth restriction (IUGR) infants different from normal infants?
IUGR infants have microscopically less branding of villi
What brings oxygenated blood and nutrients to fetus?
umbilical vein
What are the two main functions of the placenta?
- metabolism
2. function
What 3 things does the placenta metabolize for the fetus?
- glycogen
- lactate
- cholesterol
___% of O2 and ___% of glucose of maternal blood is used up for the fetus.
50%
65%
Why is the placental membrane considered a “barrier”?
compounds with large M.W. can not cross.
What human body part is the placenta relatively similar to?
small intestine
How does oxygen and many drugs move across the placental membrane?
passive diffusion
Does fetal hemoglobin have a greater or weaker binding capacity for O2?
greater
What substances enter the placenta via:
- Passive diffusion
- Facilitated diffusion
- Active transport
- Solvent drag
- Oxygen, CO2, FAs, steroids, electrolytes, fat soluble vitamins
- sugars, long chain polyunsaturated FA
- AAs, cations (Ca, Fe, I, PO4), water soluble vitamins
- electrolytes
Of the molecules that enter the placenta via passive diffusion, which is poorly transferred?
fat soluble vitamins
Why do sugars undergo carrier mediated facilitated diffusion?
–
_______ is a mechanism of teratogenesis
glycation
What two molecules enter the placenta via pinocytosis?
Fe, folate
Step by step, how does maternal malnutrition lead to fetal growth retardation?
Maternal malnutrition –> reduced blood volume expansion –> inadequate increase in cardiac output –> decreased placental blood flow (hypotension, renal disease, placental inflation) –> decreased placental size + reduced nutrient transfer –> fetal growth retardation
Fetal size is proportional to _____ size.
placental
By how much do the fetus and placenta increase in weight during the 3rd trimester?
fetus: more than 50% (last 10 weeks)
placenta: only 50%
How does the placenta compensate for the fact that it increases by a lower rate than the fetus?
placental blood flow increases
What happens during the last 4 weeks of gestation?
progressive decline in quantity of nutrients transferred per unit fetal body mass per unit time
How does the progressive decline in quantity of nutrients transferred from placenta to fetus during the last 4 weeks of gestation affect fetal growth rate?
deceleration in fetal growth rate.
What 3 things happens if the placenta fails?
- severe hypotension
- renal disease
- placental infraction (interruption of blood flow between placenta and baby)
- essential fatty acid deficiencies which leads to defects in placental function
What can placental defects lead to in the baby?
intrauterine fetal growth restriction
What is a low concentration of essential fatty acid absorption via placenta associated with?
- short gestation
2. small head circumference
Poly unsaturated fatty acids make up what % of energy devoted to brain development?
70%
Lipids make up what % of brain structure matter?
50-60%
What are the two most common poly unsaturated fatty acids found in the brain motor cortex of mammals?
- 20:4 n-6 (15%) - linoleic
2. 22:6 n-3 (21%) - DHA
What are the 4 main functions of the placenta?
- endocrine (hormone secretion)
- hormone catabolism
- nutrient storage
- protection against xenobiotics
What 4 endocrine products does the placenta secrete?
- human chorionic gonadotrophin (maintains corpus luteum which secretes estrogen & progesterone)
- human chorionic somatotrophin (placental lactogen)
- progesterone
- estrogen
- When is human chorionic gonadotrophin secreted by blastocyst?
- When is its peak secretion period via placenta?
- day 7
2. day 10 & 11