Placenta #2 Flashcards
Describe the circulation in the placenta.
-Placental villi = maternal & foetal substances exchange
–> maternal blood perfuses intervillous spaces
-Umbilical vein = oxygenated, nutrient rich - blood from placenta to foetus
-Umbilical artery = deoxygenated, nutrient depleted - blood from foetus to placenta
Mnemonic for placenta functions?
S torage
E ndocrine
R espiration
P rotection
E xcretion
N utrition
T ransfer
What storage function does placenta have?
-Metabolises glycose - stores as glycogen until required
-Synthesises & stores cholesterol
-Vitamins (which are iron & fat soluble)
What endocrine function does placenta have?
Produces:
-hCG
-hCS (human chorionic somatomammotropin)
-Progesterone
-Oestrogen
Role of hCG?
Stimulates corpus luteum to produce progesterone to maintain pregnancy
Role of hSC
-Synthesised & secreted by syncytiotrophoblast – at about the time when production of hCG begins to diminish
-Secreted primarily into maternal circulation
-Most of its functions occur at sites of action in maternal tissues
-Gives nutrition to foetus
-Also stimulates milk glands in breasts for breastfeeding
-> produced by placenta @ full term
-Regulates metabolism in pregnant woman
–> - Insulin antagonist = regulates maternal blood glucose levels to ensure optimal availability of blood glucose to meet caloric requirements of foetus
Role of progesterone in pregnancy?
-Maintains lining/causes growth of uterus endometrium (womb)
-Prevents uterine contractions
-Helps breasts get ready to make breast milk
Role of oestrogen in pregnancy?
-Produced by ovaries & later by placenta
-Helps uterus grow, maintains uterine lining
-Regulates other key hormones & triggers development of baby’s organs
-When is time to breastfeed - promotes growth of breast tissue & helps milk flow
What respiratory role does placenta have?
-Gas exchange occurs via diffusion
-High foetal Hb affinity levels
-Slight maternal alkalosis in pregnancy - assists transfer of O2 & CO2
-Bohr effect
-Haldane effect - dec. CO2 binding capacity - to maintain pregnancy - foetal Hb = v. high - must get rid of some RBCs ~ day 3 of life
What protection role foes placenta have?
-Filters substances of high molecular weight - as has semi-permeable memb
-Immunological function - naturally acquired passive immunity
-Limited barrier to infection
-Prevents antigen reactions (as separates blood circuation)
-Few bact can cross placental barrier
-BUT many viruses, parasites & protozoal diseases can! -> e.g., HIV, rubella, toxoplasmosis
–> so basal layer of placenta doesn’t stop passage of everything - alcohol, meds/drugs,
What excretion role does placenta have?
-Diffusion
-CO2 = main substance excreted from foetus
-> along with some urea & uric acid & bilirubin (yellow substance made in body’s normal process of breaking down old red blood cells
What nutritional role does placenta have?
For development - foetus requires substances from maternal diet:
-AAs & glu = growth & energy
-Ca2+ & phosphorus = bones & teeth
-Fe2+ & minerals = formation of blood
–> this depletes maternal supply
= parasitic relationship
-In later stages of pregnancy - fats & fat soluble vitamins cross placenta too
-AAs = via active transport
What is the placenta’s role in transfer of substances?
*Foetus dependent on mother
*Facilitated by - uteroplacental & fetoplacental circulation
-Diffusion
-Water soluble substances
-Endocytosis of macromolecules
-AT mechanisms - e.g., Ca2+
-Rate of transfer = by increased maternal & foetal blood flow
