Physiology of Lactation and Pregnancy Flashcards
What changes occur to the fertilized ovum from point of fertilization to implantation?
- the F.ovum divides and differentiates into a BLASTOCYST as it moves from fertilization site in UPPER oviduct to implantation site in UTERUS
What helps in the transfer of the ovum to the uterus?
- fimbriae sweeps the ovum into the oviduct
- —-ovum is then carried along the duct by smooth muscle and cilia
What is the role of the trophoblasts in the blastocyst?
- accomplishes implantation
- develops into fetal portions of the placenta
Site of fertilisation?
- ampulla of the fallopian tube
What occurs within the 3-8 days of fertilization?
- 3-5 days: transport of the blastocyst into the uterus
- 5-8 dsy: blastocyst attaches to endometrium
After attachment of the blastocyst to the endometrium, what occurs next?
- the INNER cell mass of the blastocyst develops into an embryo
- the outer cells BURROW into the uterine wall and BECOME the placenta
What is the placenta responsible for?
- prodn of several hormones to maintain the pregnancy
How does the blastocyst implant itself to the endometrium?
—cords of trophoblastic cells penetrate the endometrium
—advancing cords of the trophobl. cells tunnel DEEPER into the endometrium; carving a hole for the blastocyst (for it to sit in) ——boundaries between cells disintegrate
When the burrowing is done; the blastocyst is completely burried in the endometrium. At what day since fertilisation is the blastocyst completely buried?
- day 12
How does the deicidua form?
- after implantation; the maternal endometrium undergo a decidual reaction
What are the 3 types of decidua?
- Decidua Capsularis- around the chorion
- Decidua Parietalis - opp. uterus wall
- Decidua Basalis
What occurs in the 4th month to cause the uterine cavity to obliterate?
- the fetus becomes so large that the decidua capsularis comes in contact with decidua parietalis
Where does the placenta derive from?
- both trophoblast and decidual tissue
How does the placental villi come about ?
- trophoblast differentiate into synctiotrophoblast which invade the decidua and break down capillaries to form cavities filled with maternal blood
- —-developing embryo sends capillaries INTO the synctiotrophoblast projections to form placental villi
What contains within a villus?
- each villus contains FETAL capillaries separated from the maternal blood by a THIN LAYER OF TISSUE
What occurs at the placental villi?
2 way exchange of resp. gases, nutrients, metabolites between Mother and fetus
- functional at 5th week of pregnancy
How does the placental villi act as an arteriovenous shunt?
- as the placenta develops; it extends hair-like projections into the uterine wall—-this increases the contact area between the uterus and the placenta ; allowing MORE nutrients to be exchanged
Where is the exact arteriovenous shunt?
- Circulation within the intervillous space
Up until which gestational week, does the Corpus luteum produce progesterone?
week 10
What cells secrete HCG during pregnancy?
- trophoblast tissue
What is is structurally important about HCG with relation to other hormones?
- it shares the alpa-subunit as LH , TSH and FSH
- —–it can bind to LH receptors in the CORPUS luteum to helps drive the progesterone release and maintain the C.Luteum
Importance of maintaining the corpus luteum? `
- release of progesterone MAINTAINS the pregnancy by maintaining the endometrial lining and PREVENTING menstruation to occur!
(for first 10 weeks of pregnancy)
What do the pregnancy tests detect?
- beta subunit of HCG (antibofy variant test)
Which is more sensitive for testing hCG levels- serum or urine?
SERUM hCG levels !—best to RULE OUT PREGNANCY
—-can detect very low levels at 1-2 mIU/mL …POSITIVE within a week of conception
URINE hCG levels only detects 20-50 mIU/mL (not positive until 2 weeks or more)
What carries on secreting progesterone after the 10 weeks of secretion by the Corpus Luteum?
-the synctiotrophoblast
Name another hormone released by the synctiotrophoblast>
- Human Placental Lactogen (hPL)
- –higher levels as placenta grows
What is the main role of the hPL (aka HCS) hormone?
- resp. for making as much energy sources available for the fetus to grow
- BLOCKS the effects of insulin (raising blood glucose level/fatty acid breakdown and protein breakdown)
Why may diabetes develop during pregnancy or DM worsen during this time?
- because pregnancy is an insulin-resistant state
How is GDM excluded in women?
- through obtaining BLOOD glucose
- NOT checking for glycosuria (normal in pregnancy)
Why does total body volume expland?
as maternal blood is diverted to fill the placenta; there will be a RISE in renin leading to salt/water retention
Why may mild anemia occur in pregnancy?
- the rise in volume will be greater than the rise in red cell
- lowering hematocrit level.
Define lactation.
- process by which milk is synthesized and secreted from the mammary glands
(in resp. to infant sucking at the nipple)
The mammary gland expands extensively during pregnancy, in response to which hormones?
- estrogen
- GH
- Cortisol
- prolactin
When do prolactin levels begin to increase?
When does it plateau?
- Near the 5th week of gestation
- prolactin plateaus at a level high in LATE pregnancy (enough to initiate milk prodn)
Why does milk prodn only begin till after the pregnancy?
- estrogen, progesterone and others INHIBIT prolactin-mediated milk synthesis
(inhibition is lifted when placenta is expelled)
What neuroendocirne reflex occurs with infant suckling?
- post. pituitary release of oxytocin which stimulates the myoepithelial cells to squeeze milk from the alveoli ….allowing the milk to drain into the lactiferous ducts, into the lactiferous sinsuses and discharge through the nipple
What occurs to prolactin level after chilbirth?
- DROPS sharply
restored for a 1-hr SPIKE during each feeding —-stimulates the PRODN of milk for the next feeding
How does the placenta play the role of fetal lungs?
- exchange between maternal blood (oxygen rich) and umbilical blood
- oxygen diffuses from the maternal into FETAL circulation
- carbon dioxide follows a reverse gradient
Which vessel carries the oxygen rich blood- umbilical Vein or artery?
- Umbilical Vein reaches the fetus with oxygen rich blood
What 3 factors facilitate the supply of oxygen to the fetus?
- fetal Hb (increased affinity for O2)
- Higher Hb in fetal blood (50% more than adults)
- Bohr Effect
What is the Bohr effect?
- fetal Hb can carry more O2 in LOW pCO2 than in High pCO2
How does water and electrolytes get transported to the placenta?
- water diffuses by OSMOTIC gradient
- —-exchange increases during pregnancy up to the 35th week
- electrolytes follow H20
WHich 2 electrolytes can only only be transported to the fetus?
-iron and calcium
WHat products diffuse across the placenta?
- free diffusion of FATTY ACIDS
- diffusion of waste products based on conc. gradient
Drugs are the cause of 3% of congenital malformations. What drugs can cross the placenta?
- thalidomides, carbamazepine, tetracycline, courmarins
2. Alcohol, nicotine, heroin, cocaine, caffeine
What does HCG prevent?
- the involution of Corpus Luteum
- —-has an effect on the development of sex organs
What does human chorionic somatomammotropin bring about?
- GH like effects (protein tissue formation)
- —-decr. insulin sensitivity in moms
- involved in breast development
What is progesterone responsible for during pregnancy>
- development of DECIDUAL cells
- decr. the uterus contractility
- preparation for lactation
What are estrogens resp. for during pregnancy?
- enlargement of uterus
- breast development
- relaxation of ligaments
