Pregnancy Flashcards
day 14 of ovarian cycle =
ovulation (after LH surge)
after which… the uterine endometrium differentiates into functional tissue (secretory phase)
where does fertilization
ampulla of the fallopian tube
usually about one day after ovulation
when does implantation of blastocyst (60 cells) occur during uterine cycle
secretory phase of uterine cycle (day 21-24), about 6-7 after ovulation
blastocyst –> trophoblast
as the blastocyst differentiates, the trophoblast is formed by the outer cell layers that attach to the endometrium
tissue eventually becomes part of the placenta
2 layers of trophoblast and their function
differentiates into 2 layers…
- inner cytotrophoblast = produces cells that can become part of the syncytiotrophoblast
- retains its ability to undergo mitosis, so it can continue to produce new cells - outer syncytiotrophoblast
- cannot undergo mitosis
- consists of multinucleated cells produced by fusion of cells produced in the cytotrophoblast
Which layer of trophoblast sends finger like projections into epithelial layer of the uterus
the syncytiotrophoblast
invades the stromal layer of the endometrium
hCG
released by syncytiotrophoblast
functions similar to LH in that it rescues the corpus luteum
Decidual reaction
estrogen and progesterone produced by the corpus luteum induces the decidual reaction, in which….
the stromal cells of the uterine endometirum hypertrophy
stromal cells are not cigar shaped like they usually are, but are instead much larger
importance of the decidua
nutrient source for the embryo until the placental blood vessels develop to allow nutrient exchange between mother and fetus
in addition…
once implantation has occured, it provides a barrier to prevent the embryo from invading the uterine wall too much
endocrine function of decidua
Relaxin = functions to inhibit uterine contraction early in pregnancy and to soften the cervix before birth
(+) by hCG and occurs in the decidua, corpus luteum, and placenta
Prolactin = functions to decrease the mother’s immune response to the fetus
- –> effect on mammary gland is inhibited by high esterogen and progesterone during pregenancy…then when these levels drop after birth, prolactin is effective in stimulating lactation
- **produces small amounts of prolactin compared to maternal pituitary
Prostaglandins = produced late in pregnancy to cause contraction of the uterus and softening of the cervix
myometrium during pregnancy (general)
undergoes both hyperplasia and hypertrophy
placenta function (general)
a temporary endocrine organ
develops during pregnancy
produces and releases steroid and protein hormones designed to support pregnancy
regulations of placental hormones
are NOT regulated by maternal or fetal mechanisms
truly an independently functional endocrine organ
placenta develops by what?
develops by the invasion of the syncytiotrophoblast into the endometrium
where it comes into contact with maternal blood vessels
how are secondary villi formed
the extraembryonic mesoderm and cytotrophoblast grow into the syncytiotrophoblast
forming the secondary villi
**note: secondary villi do not contain blood vessels
after the secondary villi forms…
the cytotrophoblast grows past what…
grows past the syncytiotrophoblast
creating a cytotrophoblast shell around the entire embyro
tertiary villi develop that contain vessels of fetal circulation from the umbilical cord
difference between secondary and tertiary villi
tertiary have blood vessels
maternal portion of the placenta
decidua basalis, made from decidual cells…
contributes to the basal plate and the placental septa
fetal portion of the placenta
chorion
contributes the following components
- cytotrophoblast
- syncytiotrophoblast
- extraembryonic mesoderm
- fetal endothelial cells
- chorionic plate
- chorionic vili (both free and anchoring villi - anchored to maternal side)
placental barrier from maternal to fetal side
consists of…
syncytiotrophoblasts
cytotrophoblasts
connective tissue (extraembryonic mesoderm)
fetal endothelial cells
what substances CAN cross the placenta
any molecule less than 600 Daltons can freely diffuse
gases and nutrients (glucose, amino acids, and some proteins)
transferrin (carry iron to fetus)
steroid hormones
CO2 and other fetal waste material
maternal antibodies, mostly in the form of IgG: function to provide passive immunity to the baby
alcohol, some drugs, and some viruses
where does placenta break off after birth
at the level of the decidua basalis
leaving the basal layer of the endometrium in place
parallels between the HPA axis and the relationship between syncytiotrophoblast and cytotrophoblast
cytotrophoblasts are analogous to the hypothalamus
syncytiotrophoblast are analogous to the anterior pituitary gland
hormones produced by the cytotrophoblast
IGF-1 and IGF-2 –> function to increase proliferation and differentiation
GnRH, CRH, TRH, and somatostatin –> act on the syncytiotrophoblast
hormones produced by the syncytiotrophoblast
hCG
human chorionic ACTH
human placental GH
human chorionic thyrotropin (similar actions to TSH)
progesterone
estrogens
human chorionic somatomammotropin (hCS), aka human placental lactogen (hPL)
inhibin A
actions of progesterone produced by the syncytiotrophoblasts
decreases the mother’s immune response to the fetus
produces precursor substances that fetal adrenal glands can use to produce needed hormones
inhibits uterine contractions
causes mammary gland development
**produced in placenta from maternal cholesterol
what can progesterone NOT be converted to within the placenta
cannot be converted to androgens in the placenta, because the needed enzymes for those reactions are not present
actions of estrogens produced by the syncytiotrophoblastss
= estriol, estradiol, and estrone
function to increase uterine SmM growth and mammary gland development
made using precursors by the fetal adrenal gland
major estrogen produced during pregnancy
estriol
actions of hCS (or hPL) produced by syncytiotrophoblasts
shunts nutrients preferentially to the fetus
actions of inhibin A produced by syncytiotrophoblasts
functions to decrease maternal FSH
since you don’t need to stimulate follicle developement during pregnancy
hCG progression in pregnancy
levels rise shortly after pregnancy occurs
remains at a high level throughout pregnancy
progesterone progression in pregnancy
initially produced by the corpus luteum - which is being maintained by hCG
around the end of the 1st trimester, the placenta takes over progesterone production and levels rise significantly
estrogens progression in pregnancy
rise significantly during pregnancy…throughout whole time
hCS progression during pregnancy
increases throughout pregnancy
prolactin progression during pregnancy
increases throughout pregnancy (mostly by maternal pituitary gland)
high progesterone and estrogen inhibit prolactin effects on the mammary gland until birth
measuring fetal and placental health
estriol –> useful assay to determine fetal health
placental production of estriol is dependent on the precursors produced in the fetus
hCG = a hormone produced by the syncytiotrophoblasts of the placenta - used to determine placental health
why are progesterone levels not the best way to determine placental or fetal health
it is also produced in small amounts by the corpus luteum of pregnancy (even after the 1st trimeseter)
steroid contraceptives (the pill)
mechanism
function to inhibit the development of ovarian follicles and thus inhibit ovulation
presence of progesterone in these pills provides negative feedback on the hypothalamus –> reducing the pulse frequency of GnRH
also (-) FSH and LH release from anterior pituitary gland –> preventing follicles from developing
with no follicular development –> no large increase in estrogen –> no LH surge –> no ovulation
also increase viscosity of cervical mucosa
estrogen included in many of these pills stabilize the endometrium and prevents breakthrough bleeding - in addition to a role in inhibiting the development of ovarian follicles
types of steroid contraceptives
combination estrogen-progestin
= constant concentrations over 21 day period followed by 7 day rest
phasic estrogen-progestin
= varying concentrations throughout the 21 day period and 7 days of placebo
progestin only = contant progesterone dose daily
intrauterine contraceptive devices
prevent blastocyst implantation by altering the endometrial lining
some release progesterone, modifying the endometrial lining
barrier methods
condoms, foam, and diaphragms
prevent fertilization by either interfering with the acess of sperm to the uterine cavity or destroying sperm in the vaginal cavity
sterilization
surgically disrupt the continuity of the fallopian tubes
impairing access of the fertilized ovum to the uterine cavity and implantation
abortive contraception
antiprogestin mifespristone produces an increase in prostaglandin F2-alpha synthesis
leading to expulsion of the embyro
rhythm contraception
relies on changes in mucus thickness and body temperature throughout the mesntrual cycle
indicating a ‘safe’ period for intercourse
fertility drugs (general)
stimulate the development of ovarian follicles and ovulation
prepare the endometrium for implantation of a blastocyst
progesterone fertility drug
used when serum progesterone is low
estrogen partial antagonists (Clomiphene)
stimulates GnRH
gonadotropins (hMG) fertility drugs
literally made from LH and FSH extracted from the urine of post-menopausal women (because they have high levels)
GnRH agonists
fertility drugs
allow control LH and FSH release, thus controlling the timing of ovulation
GnRH antagonists fertility drugs
prevent LH and FSH release - thus controlling the timing of ovulation
bromocriptine (dopamine agonist)
fertility drugs
decreases prolactin from the anterior pituitary
thus reducing the inhibitory effect high prolacitn levels have on estrogen
also decreases the inhibition of ovulation caused by high prolactin levels
