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)
