female reproductive Flashcards

Question

Oogenesis and follicular development

Answer 1

- Formation of gametes in ovary - Oogenesis begins before females are born - Essentially same steps of meiosis as spermatogenesis - During early fetal development, primordial (primitive) germ cells migrate from yolk sac to ovaries - Germ cells then differentiate into oogonia – diploid (2n) stem cells - Before birth, most germ cells degenerate – atresia - A few develop into primary oocytes that enter meiosis I during fetal development - Each covered by single layer of flat follicular cells – primordial follicle - About 200,000 to 2,000,000 at birth, 40,00 remain at puberty, and around 400 will mature during a lifetime

Answer 2

Each month from puberty to menopause, FSH and LH stimulate the development of several primordial follicles -Usually, only one reaches ovulation Primordial follicles develop into primary follicles - Primary oocyte surrounded by granulosa cells - Forms zona pellucida between granulosa cells and primary oocyte - Stromal cells begin to form theca folliculi Primary follicles develop into secondary follicles - Theca differentiates into theca interna secreting estrogens and theca externa secreting androgens - Granulosa cells secrete follicular fluid in antrum - Innermost layer of granulosa cells attaches to zona pellucida forming corona radiata

Answer 3

Secondary follicle becomes mature (graffian) follicle - Just before ovulation, diploid primary oocyte completes meiosis I - Produces 2 unequal sized haploid (n) cells – first polar body is discarded and secondary oocyte At ovulation, secondary oocyte expelled with first polar body and corona radiata If fertilization does not occur, cells degenerate If a sperm penetrates secondary oocyte, meiosis II resumes Secondary oocyte splits into 2 cells of unequal size – second polar body (also discarded) and ovum or mature egg Nuclei of sperm cell and ovum unite to form diploid zygote

Answer 4

S = 4 viable sperm with 3-4% error rate O = 1 viable gamete + 3 polar bodies with 20% error rate unequal divisions ensure oocyte has ample nutrients for 6-7 day journey to uterus polar bodies degenerate and die

Answer 5

Ovarian cycle – series of events in ovaries that occur during and after maturation of oocyte Uterine (menstrual) cycle – concurrent series of changes in uterine endometrium preparing it for arrival of fertilized ovum

Answer 6

Gonadotropin-releasing hormone (GnRH) - Secreted by hypothalamus controls ovarian and uterine cycle - Stimulates release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from anterior pituitary FSH (anterior pituitary) - Initiate follicular growth - Stimulate ovarian follicles to secrete estrogens

Answer 7

LH (anterior pituitary) Stimulates further development of ovarian follicles Stimulate ovarian follicles to secrete estrogens Stimulates thecal cells of developing follicle to produce androgens to be converted into estrogens Triggers ovulation Promotes formation of corpus luteum – produces estrogens, progesterone, relaxin and inhibin

Answer 8

Estrogens secreted by ovarian follicles Promote development and maintenance of female reproductive structures and secondary sex characteristics Increases protein anabolism including building strong bones Lowers blood cholesterol Inhibit release of GnRH, LH and FSH Progesterone Secreted mainly by corpus luteum Works with estrogens to prepare and maintin endometrium for implantation and mammary glands for milk production Inhibits secretion of GnRH and LH

Answer 9

Relaxin Produced by corpus luteum Relaxes uterus by inhibiting contraction of myometrium At end of pregnancy, increases flexibility of pubic symphysis and dilates uterine cervix Inhibin Secreted by granulosa cells of growing follicles and by corpus luteum Inhibits secretion of FSH and LH

Answer 10

Typical duration 24-35 days Assume a duration of 28 days Menstrual phase Preovulatory phase Ovulation Postovulatory phase

Answer 11

Roughly first 5 days of cycle First day of menstruation is day 1 of new cycle Events in ovaries Under FSH influence, several primordial follicles develop into primary follicles ad then into secondary follicles Takes several months Follicle that begins to develop in one cycle may not mature for several cycles later Events in uterus Menstrual discharge occurs because declining levels of estrogens and progesterone stimulate release of prostaglandins causing uterine spiral arterioles to constrict Cells deprived of oxygen begin to die Only stratum basilis remains

Answer 12

More variable in length Lasts from days 6-13 in a 28 day cycle Events in ovaries Some of secondary follicles begin to secrete estrogens and inhibin Dominant follicle – one follicle outgrown all others -Estrogens and inhibin of dominant follicle decrease FSH causing other follicles to stop growing -Fraternal (nonidentical) twins result when 2 or 3 secondary follicles become codominant and are ovulated and fertilized at the same time Normally, one dominant follicle becomes the mature (graffian) follicle In ovarian cycle, menstrual and preovulatory phases are termed follicular phase because follicles are growing

Answer 13

Estrogens stimulate repair of endometrium Cells of stratum basalis undergo mitosis to form new stratum functionalis Thickness of endometrium doubles In uterine cycle, preovulatory phase is the proliferative phase because endometrium is proliferating

Answer 14

Rupture of mature (graffian) follicle and release of secondary oocyte Day 14 of 28 day cycle High levels of estrogens exert a positive feedback effect on cells secreting LH and GnRH Ovary wall ruptures, expels secondary oocyte with its corona radiata to peritoneal cavity Mittelschmerz - twinge of pain sometimes felt at ovulation 1–2% of ovulations release more than one secondary oocyte, which, if fertilized, results in fraternal twins Identical twins result from fertilization of one oocyte, then separation of daughter cells

Answer 15

Duration most constant of phases Lasts for 14 days in 28 day cycle (day 15-28) Events in one ovary After ovulation, mature follicle collapses to form corpus luteum under the influence of LH Secretes progesterone, estrogen, relaxin and inhibin In the ovarian cycle, this is the luteal phase

Answer 16

If oocyte not fertilized, corpus luteum lasts 2 weeks - Degenerates in corpus albicans - As levels of progesterone, estrogens and inhibin decrease, release of GnRH, FSH, and LH rise sue to loss of negative feedback - Follicular growth resume as new ovarian cycle begins If oocyte is fertilized, corpus luteum lasts more than 2 weeks -Human chorionic gonadotropin (hCG) produced by chorion of embryo about 8 days after fertilization stimulates corpus luteum

Answer 17

Progesterone and estrogens produced by corpus luteum promote growth of endometrium Because of secretory activity of endometrial glands, this is the secretory phase of uterine cycle Changes peak about 1 week after ovulation when an embryo might arrive in uterus If fertilization does not occur, levels of progesterone and estrogens decline due to degeneration of corpus luteum Withdrawal of estrogens and progesterone due to the degenerating corpus lutem causes menstruation

Answer 18

Ovaries secrete small amounts of estrogens Estrogen inhibits release of GnRH Onset of puberty linked to amount of adipose tissue via hormone leptin If leptin levels adequate hypothalamus less sensitive to estrogen as puberty nears; releases GnRH in rhythmic pulse-like manner --> FSH and LH release -->ovarian hormone release

Answer 19

Gonadotropin levels increase ~ four years; no ovulation; no pregnancy Then adult cyclic pattern achieved and menarche occurs First menstrual period ~ Three years before cycle regular and all ovulatory

Answer 20

Promote oogenesis and follicle growth in ovary Exert anabolic effects on female reproductive tract Support rapid but short-lived growth spurt at puberty Induce secondary sex characteristics - Growth of breasts - Increased deposit of subcutaneous fat (hips and breasts) - Widening and lightening of pelvis Metabolic effects (not true secondary sex characteristics) - Maintain low total blood cholesterol and high HDL levels - Facilitate calcium uptake

Answer 21

Progesterone works with estrogen to establish and regulate uterine cycle Promotes changes in cervical mucus Effects of placental progesterone during pregnancy -Inhibits uterine motility -Helps prepare breasts for lactation

Answer 22

Initiated by touch and psychological stimuli Clitoris, vaginal mucosa, bulbs of vestibule, and breasts engorge with blood; nipples erect Vestibular gland secretions lubricate vestibule Orgasm accompanied by muscle tension, increase in pulse rate and blood pressure, and rhythmic contractions of uterus

Answer 23

Has occurred when menses have ceased for an entire year No equivalent to menopause in males -Males continue to produce sperm well into eighth decade of life, though numbers and motility decrease

Answer 24

Atrophy of reproductive organs and breasts Irritability and depression in some Hot flashes as skin blood vessels undergo intense vasodilation Gradual thinning of skin and bone loss Increased total blood cholesterol levels and falling HDL

Answer 25

Women's Health Initiative research reported increased risk of heart disease (51%), invasive breast cancer (24%), stroke (31%), dementia (risk doubled) Smallest does for shortest time alright to reduce symptoms if no breast cancer or mutated BRCA gene