Post on 24-Dec-2015
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Female Reproductive Cycle
2 parts:1. Ovarian Cycle
1. series of events in ovaries occurring during & after maturation of oocyte
2. Uterine (Endometrial) Cycle1. concurrent with ovarian cycle2. series of changes in endometrium to repare
it for implantation of fertilized egg
Hormonal Regulation
Hypothalamus secretes GnRH (gonadotropin-releasing hormone) that controls both the ovarian & uterine cycles
GnRH stimulates release of FSH & LH from anterior pituitary
FSH LH
initiates follicle growth
stimulates: follicles to release
E granulosa cells to
turn androgens E
stimulates : further development
of follicles release of E from
follicles release of androgens
from theca cells @ midcycle LH surge
triggers ovulation corpus luteum E, P,
relaxin, inhibin
Effects on Ovaries
Estrogens
3 of 6 different estrogens are present in significant amts:
1. ß estradiol2. Estrone3. Estrial
most abundant in non-pregnant female made from cholesterol in ovaries
Functions of Estrogens
1. promote development &maintenance of female reproductive structures, 2◦ sex characteristics
2. increase protein anabolism working synergistically with hGH
3. lowers cholesterol (1 reason females <50 yo have lower risk of CAD)
4. moderate levels inhibit release of GnRH, FSH, LH (negative feedback loop)
Progesterone
secreted by corpus luteumwith E prepares endometrium for
implantation & breasts for lactation
Relaxin
produced by corpus luteuminhibits contractions of myometriumduring pregnancy, placenta secretes more
relaxin…@ end of pregnancy it increases flexibility of pubic symphysis & may help dilate cx
Inhibin
secreted by granulosa cells of growing follicles & by corpus luteum after ovulation
action: inhibits secretion of FSH & to lesser extent LH
Phases of the Menstrual Cycle
1. Menstrual Phase2. Preovulatory Phase
in ovaries called follicular phase in uterus: proliferative phase
3. Ovulation4. Postovulatory Phase
in ovaries called luteal phase in uterus: secretory phase
Menstrual Phase
aka menstruation, menses~1st 5 d of cycle (d 1 of flow = day 1 of cycle)Ovaries:
FSH causes several primordial follicles to develop 1◦ follicles 2◦ follicles
Uterus: declining E & P levels prostaglandins
constriction of uterine spiral arterioles O deprived tissue death & shedding 50 – 150 mL of blood, tissue fluid, mucus, epithelial cells (entire stratum functionalis sloughs off)
Preovulatory Phase
time between end of menses ovulationmost variable length in time (reason cycles
vary in length)Ovaries:
follicles secrete E & inhibin d 16 one 2◦ follicle in 1 of the 2 ovaries becomes
the dominant follicle (secretes more E & inhibin decreases FSH)
dominant follicle (Graafian) enlarges until ovulation:~2cm
Preovulatory Phase (Proliferative)
Uterus: E stimulates repair of endometrium
producing new stratum functionalis new endometrial glands form endometrium thickens from ~4 to 10 mm
Ovulation
d 14 in 28 d cycle2◦ oocyte surrounded by zona pellucida &
corona radiatahigher levels of E @ end of preovulatory
phase have + effect on cells that secrete LH & GnRH: their increase leads to ovulation
OTC test for LH surge used to predict ovulation
Mittleschmerz
pain noted @ time of ovulationcaused by small amt of blood that leaks into
pelvic cavity from ruptured follicle
Postovulatory Phase (Luteal)
time between ovulation & onset of next mensesMost constant part of cycle = 14 days (d15 – 28)Ovary:
under influence of LH, granulosa cells transformed corpus luteum cellswhich secrete E, P, relaxin, inhibin
if oocyte not fertilized: corpus luteum lasts 2 wks corpus albicans
+ fertilization: corpus luteum persists until “rescued” by hCG (human chorionic gonadotropin) which is made by chorion of embryo @ ~ 8d after fertilization
Postovulatory Phase (Secretory)
Uterus: P & E made by corpus luteum promote:
growth & coiling of endometrial glands vascularization of superficial endometrium thickening of endometrium (12 – 18 mm) these changes peak 1 wk after ovulation if no fertilization levels of P & E decline
which eventually causes menstruation
Homeostatic Imbalances
Dysmenorrhea painful menses
Amenorrhea absence of menses #1 reason = pregnancy
Endometriosis disorder in which endometrium grows
outside uterus +/- painful can cause infertility due to scarring
Embryonic Period
Fertilization: Nuclei from sperm merges with nuclei from
2◦ oocyte forming a diploid nucleus Fallopian tube normal site of fertilization
w/in 12 -24 hrs after ovulation sperm can remain viable up to 48 hrs after
deposition in vagina
Fertilization
sperm must penetrate 2 layers:1. corona radiata
granulosa cells that surround 2◦ oocyte
2. zona pellucida clear glycoprotein layer between corona
radiata & oocyte’s plasma membrane
Fertilization
ZP3: 1 of glycoproteins acts as sperm receptor
acrosomal reaction: occurs when ZP3 binds to specific membrane protein on sperm head plasma membrane release of contents of acrosome
Acrosomal Reaction
acrosomal enzymes digest a path thru zona pellucida
lashing flagella of sperm pushes it forwardseveral sperm bind to ZP3 molecules but only
1st sperm to penetrate zona pellucida & reach plasma membrane of oocyte “wins”
once diploid nucleus formed its called a zygote
Cleavage of the Zygote
rapid M phase but no growth1st division begins ~24 hrs after fertilization
taking 6 hrs to complete, following divisions take less time
~2 d after fertilization = 4 cells~ 3 d after = 16 cellscells get progressively smaller, & are called
blastomeresmorula (mulberry) solid sphere of cells, still
surrounded by zona pellucida & still about size of original zygote
Blastocyst Formation
~ end of 4th d: # of cells in morula increase as it is still moving thru fallopian tube enter uterine cavity on d 4-5
glycoprotein secretions fromendometrial glands enter morula providing nourishment
@ ~ 32 cell size, fluid enters morula & collects between blastomeres forming fluid-filled cavity = blastocyst cavity (up to ~100 cells) & now called a blastocyst or blastula (still ~ same size as original zygote)
Blastocyst Forms Layers
2 distinct structures form:1. Inner cell mass
eventually becomes embryo
2. Trophoblast ultimately forms fetal portion of placenta 5th d: blastocyst digests hole thru zona
pellucida & squeezes out
Implantation
attachment of blastocyst to endometriumafter implantation endometrium becomes
modified & is called decidua
hCG is Produced
hCG: human chorionic gonadotropinProduced by trophoblast starting on d 6hCG causes endometrium to grow &
proliferatehCGprevents the menstrual cycle from
occuringreason female misses her menses when she is
pregnant
Gastrulation
@ end of cleavage stage, cells making up the blastula move
surface proteins help cells recognize each other & help sort cells
3 layers of gastrula formed: called the 3 germ layers
EndodermMesodermEctoderm
Extraembryonic Membranes
develop from the germ layers but are NOT part of the embryo (lost at birth)
lie outside embryo & provide protection & nourishment
4 components:1. chorion2. amnion3. allantois4. yolk sac
Placentation
formation of the placentasite of exchange of nutrients & wastes
between the mother & fetusalso functions as protective barrier &
produces several hormones to maintain pregnancy (hCG)
Embryonic Period Fetal Period
1st thru 8th wkcharacterized by
development of structures (organs)
begins @ 9th wk & goes until birth @ 38 wks (from fertilization)
characterized by growth & development of structures formed in embryonic period
Embryo/ Fetus
Maternal Changes in Pregnancy
uterus nearly fills abdominal cavityGI tract compressed may cause heartburn,
constipationpressure on bladder causes frequency &
urgencycompression of inferior vena cava may cause
varicose veins, &/or edema in legscompression on renal vessels may cause
elevated BP (renal hypertension)
Maternal Hormone Changes During Pregnancy
pregnancy maintained by hCG, E, & Prelaxin increases flexibility of pubic
symphysishCS (human chorionic somatomammotropin)
contributes to:breast developmentprotein anabolismcatabolism of glucose & fatty acids
Labor
process by which fetus is expelled from uterus
true labor involves dilation & thinning of cxfalse labor may have painful contractions but
there are no cervical changes
Adjustments Infant Makes at Birth
Infant’s respiratory & cardiovascular systems undergo changes to enable them to become self-supporting
Maternal Breast Changes
hormonal changes, increased blood flow, & changes in breast tissue cause breast to feel heavy, swollen, or sore
breast tenderness commonly starts w/in 4 wksareolas enlarge & darkenColostrum the yellowish1st milk your baby gets
may leak out any time after 3rd mo contains Ig A antibodies, protein, fat-
soluble vitamins, minerals replaced by milk after 2 – 4 days baby
nursing
Prolactin Oxytocin
made in anterior pituitary
release controlled by dopamine
action: activates mammary glands to make milk
several minutes of baby nursing stimulates release
made in hypothalamus & stored in posterior pituitary
baby nursing stimulates its release
action: milk let down
Lactation Hormones