Lecture 17: Female Reproductive Physiology Flashcards
what is oogenesis
-Formation of gametes within the ovaries
-Begins before birth with meiosis; Accelerate at puberty; Ends at menopause
-During fetal devpt, Primordial germ cells migrate from the yolk
sac to the ovaries, and
differentiate into oogonia
what are the steps in oogenesis
- mitosis of oogonium (divide into 2)
- Meiosis I: between 3 & 7 months of fetal development the primary oocytes prepare to undergo meiosis, each month after the ovarian cycle begins some of the primary oocytes are stimulated to undergo further development, meiosis I is then completed yeilding a first polar body and a secondary oocyte
- Meiosis II: each month after ovarian cycle begins, one secondary oocyte leaves the ovary suspended in metaphase of meiosis II, at fertilization a second polar body forms and the fertilized secondary oocyte is then called a mature ovum
slide 4
ovarian follicles: specialized structures within cortex, growth of oocyte and meiosis I
slide 4
activated-> maturation (more components of cell are present)-> mature (more specialized cell)
what are the ovarian follicular stages
-at ovulation, both secondary oocyte, a polar body and a corona radiata are released into the pelvic cavity, and hten swept into uterine tube
-sper, presence/fertilization occurs, secondary oocyte continues into meiosis II, an ovum and a secondary polar body form, ovum becomes a zygote with its nucleus unites with that of sperm
-absence of fertilization= cells degenarate
review slide 6 of comparison between spermatogenesis and oogenesis
what is the female reproductive cycle (FRC)
-females experienced repeated. changes in ovaries and urterus per month
-involves oogenesis and uterine preparation to receive fertilized ovum
what does the female reproductive cycle involve
-ovarian cycle: changes that occur during and after maturation of the oocyte
-uterine cycle: changes in the endometrium that prepare it for implantation of the developing embryo
-hormonal changes: changes in breasts and cervix
what is the ovarian cycle
-A monthly (~28 day) series of events associated with maturation of egg
-Two consecutive phases, with ovulation occurring midcycle btw them
I. Follicular phase: period of vesicular follicle growth (days 1–14)
II. Luteal phase: period of corpus luteum activity (days 14–28)
-Only 10–15% women have 28-day cycle
-Follicular phase varies, but luteal phase is always 14 days from ovulation
to end of cycle
what happens in the follicular phase
-Graafian follicle creates bulge in ovary
-Oocyte and its follicular cells project into antrum: Surrounded by granulosa cells & Adjacent stromal cells form layer of thecal
endocrine cells that produce estrogens
-Rising LH levels prompt
completion of meiosis I
-Corona radiata formation: granulosa cells that remain
associated with secondary oocyte
what is ovulation
-Inflating ovary walls rupture, Graafian follicle releases 2o oocyte with its corona radiata into pelvic cavity
-Via ciliary action, Oocyte are swept into uterine tube by fimbriae
-1–2% of ovulations release more than one 2o oocyte, if fertilized, results in fraternal twins
-Identical twins result from fertilization of one oocyte, then separation of
daughter cells
what happens in the luteal phase
Corpus Luteum Formation:
-Forms from remaining granulosa cells under stimulation of LH
-Appears yellow in color due to cholesterol
-Cholesterol is converted to progesterone – prepares uterus for pregnancy
-Secretes moderate amounts of estrogens
-Begins degenerating ~12 days after ovulation
Corpus Albicans:
-Produced from nonfunctional corpus luteum as fibroblasts invade and form scar tissue
-Marks end of ovarian cycle
what is the urterine (menstrual cycle)
-repeating series of changes in endometrium
-lasts from 21 to 35 days. averaging 28 days
-menarche: first unterine cycle; begins at puberty (age 11 to 12)
what are the three phases of uterine cycle
menstrual, proliferative, and secretory phase
-menstrual and proliferative phases: during ovarian follicular phase
-secretpry phase: during ovarian luteal phase
describe the menstrual phase
-Degeneration of endometrial functional layer (stratum functionalis)
-Occurs in patches; Leads to menstruation
-Caused by constriction of spiral arteries
-Reducing blood flow, O2, and nutrients → weakened arterial walls → rupture →
releasing blood into CTs of functional layer
-Ovarian hormones are at the lowest
Menses
-Entire functional layer is lost through external os and vagina
-Only functional layer is affected, deeper, stratum basalis is supplied by straight arteries
-Lasts 1-5 days
describe the proliferativee phase
-Epithelial cells of uterine glands: Multiply and spread across endometrial surface & Restore integrity of uterine epithelium
-Further growth and vascularization: Completely restore stratum functionalis
-Occurs at same time as enlargement of Graafian ovarian follicles
-Stimulated and sustained by estrogens secreted by devping ovarian follicles
-Entire stratum functionalis is highly vascularized: Small arteries spiral toward inner surface
describe the secretory phase
-Uterine glands enlarge, increasing rates of secretion
-Arteries of uterine wall: Elongate and spiral through functional layer
-Begins at ovulation and persists as long as corpus luteum remains intact
-Secretion peaks about 12 days after ovulation; Generally, lasts 14 days
-Ends as corpus luteum stops producing hormones
how does estrogens do
-promote development & maintenance of female reproductive structures and secondary sex characteristics
-increase protein anabolism
-lower blood cholesterol
-stimulate proliferation of stratum basalis to form a new stratum functionalis after menstruation occurs
-moderate levels inhibit release of GnRH, FSH, and LH
what does inhibin do
inhibits release of FSH (follicle stimulating hormone)
what does relaxin do
-inhibits contractions of uterine smooth muscles
-during labour, increases flexibility of pubid symphysis and dilates uterine cervix
what does progesterone do
-stimulates endometrial glands to secrete glycogen and lipids, which serve as an initial nutrient source for a fertilized egg
-high levels inhibit release of GnRH, FSH, and LH
what is the female sexual response
-Initiated by touch and psychological stimuli
-Clitoris, vaginal mucosa, bulbs of vestibule, and breasts engorge with blood; nipples become erect
-Vestibular gland secretions lubricate vestibule
describe the 4 phases of female sexual response cycle
- excitement phase: vasocongestion swells the vaginal tissue, the clitoris, and the area surrounding the opening of the vagina, vagina; lubrication appears, the inner two-thirds of the vagina expand and the vaginal walls thicken and turn a deeper colour
- plateau phase: the inner two-thirds of the vagina fully expand, the outer third of the vagina thickens, the clitoris retracts behing its hood and the uterus elevates and increases in size
- orgasm phase: contractions of the pelvic muscles surrouding the vagina occur
- resolution phase: multiple orgasms may occur if the woman desires it and sexual stimulation continues
what is the female orgasm accompanied by
-Peristaltic contractions of uterine and vaginal walls
-Rhythmic contractions of bulbospongiosus and ischiocavernosus muscles
-Increase in pulse rate and BP
-Females have no refractory period after orgasm; can experience multiple orgasms in single sexual experience
describe fertilization
-Fertilization: sperm’s chromosomes combine with those of secondary oocyte to form fertilized egg, called a zygote
Before fertilization can occur, sperm must reach secondary oocyte
-Oocyte viable for 12 – 24 hours
-Sperm viable 24 – ~72 hours after ejaculation
-For fertilization to occur, coitus (sex) must occur no more than 2 days before and at least 24 hours after ovulation
describe sperm transport and capacitation
-Capacitation before Penetration into Oocyte: Motility must be enhanced, and cell membranes must become fragile enough to release hydrolytic enzymes
-Secretions of female tract help to weaken and thin out acrosome membrane
-Sperm have olfactory receptors that follow chemical trail released by egg or surrounding cells
-Sperm “sniff” their way to oocyte
what are the steps in acrosomal reaction and sperm penetration
- approach: acrosome releases enzymes
- acrosomal reaction: oocyte and sperm plasma membranes fuse
- granules release enzymes that make the zona pellucida impenetrable
- binding & fusion: sperma nucleus engulfed by oocyte cytoplasm
what are the steps in conception
- ovulation 2. fertilization 3. cleavage 4. cleavage 5. implantation
-Fertilization of an egg by a sperm, occurs in the oviduct
-The resulting zygote begins to divide by mitosis in a process called cleavage
-Division of cells gives rise to a blastocyst, a ball of cells with a central cavity
-After blastocyst formation, embryo implants into the endometrium
describe how urine shows pregnant on pregnancy tests
-The embryo releases human chorionic gonadotropin (hCG) → prevents menstruation
* Some hCG passes into the urine, where it can be
detected by early pregnancy tests
what is pregancy or gestation
it is the condition of carrying one or more embryos in the urterus
-average 266 days (38 weeks, ~ 9 months) in humans, divided into three equal trimesters
describe the first trimester
-Time of most radical change for both mother and embryo
-Implanted embryo secretes hormones that regulate the mother’s reproductive system
-One such hormone, human chorionic gonadotropin (hCG) maintains secretion of progesterone and estrogens during early pregnancy
-During first 2-4 wks, the embryo obtains nutrients directly from endometrium
-Meanwhile, the outer layer of blastocyst, the trophoblast, mingles with the endometrium and eventually forms the placenta
-Blood is carried from embryo to placenta and vice versa through umbilical vessels
what is organogenesis and what does it occur
the first trimester is main period of organogenesis, development of the body organs
-all major structures are present by week 8, and the embryo is called a fetus
what changes occur in a mother in the first trimester
-Mucus plug to protect against infection
-Growth of the placenta and uterus
-Cessation of ovulation and the menstrual cycle
-Breast enlargement
-Nausea is also very common
what happens in the second trimester
-the fetus grows and is very active
-the mother may feel fetal movements
-the uterus grows enough for the pregnancy to become obvious
what happens in the thrid trimester
the fetus grows and fills the space within the embryonic membranes
what happens in labour
a series of strong, rhythmic uterine contractions that push the fetus & placenta out of the body
-regulated by prostaglandins and hormones: estradiol & oxytocin
what are the three stages of labour
a) Thinning and opening, or dilation, of the cervix
b) Expulsion or delivery of the baby
c) Delivery of the placenta
* Postnatal care in mammals includes lactation, the production of milk
describe the positive feedback system in labour
- estradiol from the ovaries activates oxytocin receptors on uterus
- oxytocin from fetus and mother’s posterior pituitary: stimulates the uterus to contract with stimulates more oxytocin production & the oxytocin also stimulates the placenta to make prostaglandins which stimulates more contractions of the uterus
what are some contraceptions methods
- Abstinence
- Barrier methods
- Intrauterine devices
- Chemical and surgical methods
review slide 31
review slide 32
what is amenorrhea
absence of menstruation
-primary amenorrhea: failure ot initiate menstruation
-secondary amenorrhea: transient, interruption of 6 months or more, caused by several factors including drastic weight loss and emotional stress
list some other conditions associated with menstruation
-dysmenorrhea: very painful menstruation
-oligomenorrhea: abnormally infrequent and scanty menstrual flow
-polymenorrhea: menstruation at abnormally frequent intervals
how can extremely strenuous physical activity delay menarche in girls
- Can cause amenorrhea, cessation of menstruation
- Female athletes have little body fat; adipose cells are needed to convert adrenal androgens to estrogens and produce leptin that plays role in puberty
- Lack of leptin can shut down reproductive cycles
- Can reverse if woman increases body fat
