Female Reproductive System BIOL 314 PDF

Female Reproductive System BIOL 314 1  Introduction The female reproductive system is much more complex than the male system because it serves more purposes – Produces and delivers gametes – Provides nutrition and safe harbor f...

Female Reproductive System BIOL 314 1  Introduction The female reproductive system is much more complex than the male system because it serves more purposes – Produces and delivers gametes – Provides nutrition and safe harbor for fetal development – Gives birth – Nourishes infant Female system is more cyclic, and hormones are secreted in a more complex sequence 2  The Genitalia Internal genitalia – Ovaries, uterine tubes, uterus, and vagina External genitalia – Clitoris, labia minora, and labia majora Occupy the perineum Primary sex organs – Ovaries Secondary sex organs – Other internal and external genitalia 3  The Ovaries 1 Ovaries —female gonads that produce egg cells (ova) and sex hormones – Almond-shaped and nestled in the ovarian fossa of posterior pelvic wall – Tunica albuginea capsule, like on testes – Outer cortex where germ cells develop – Inner medulla occupied by major arteries and veins – Each egg develops in its own fluid-filled follicle – _____________: bursting of the follicle and releasing of the egg 4  The Uterine Tubes 1 Uterine tube (oviduct) or (fallopian tube) Canal about 10 cm long from ovary to uterus Muscular tube lined with ciliated cells – Highly folded into longitudinal ridges 5  The Uterine Tubes 2 __________________: flared, trumpet-shaped distal (ovarian) end Fimbriae: feathery projections on infundibulum Ampulla: middle and longest part Isthmus: narrower end toward uterus 6  The Uterus 1 Uterus —thick muscular chamber that opens into roof of the vagina – Usually tilts forward over urinary bladder – Harbors fetus, provides a source of nutrition, and expels the fetus at the end of its development – Pear-shaped organ Fundus —broad superior curvature Body (corpus) —middle portion __________ —cylindrical inferior end 7  The Uterus 2 Lumen is roughly triangular – Upper two corners are openings to uterine tubes – Lower apex is internal os – Not a hollow cavity, but a potential space in nonpregnant uterus Cervical canal connects lumen of uterus to vagina – Internal os —superior opening of canal into body of uterus – External os —inferior opening of canal into vagina Cervical glands: secrete mucus that prevents spread of _________________ from vagina to uterus 8  Uterine Wall 1 Uterine wall: perimetrium, myometrium and endometrium – Perimetrium —external serosa layer – Myometrium —middle muscular layer Constitutes most of the uterine wall Composed mainly of _____________________ – Produces labor contractions, expels fetus 9  Uterine Wall 2 Endometrium —inner mucosa – Simple columnar epithelium, compound tubular glands, and a stroma populated with leukocytes, macrophages, and other cells _____________________—superf icial half, shed each menstrual period Basal layer (stratum basalis)—deep layer, stays behind and regenerates a new functional layer with each menstrual cycle – During pregnancy, endometrium is the site of attachment of the embryo and forms the maternal part of the placenta from which the fetus is nourished 10  The Vagina 1 Vagina (birth canal) —8 to 10 cm distensible muscular tube – Allows for discharge of menstrual fluid, receipt of penis and semen, and birth of baby – Outer adventitia, middle muscularis, and inner mucosa – Tilted posteriorly between rectum and urethra – Vagina has ______________ Transudation lubricates vagina—“vaginal sweating” – Serous fluid through its walls and by mucus from the cervical gland above it 11  The Vagina 2 – Fornices: blind-ended spaces at top of vagina that extend slightly beyond the cervix – Transverse friction ridges (vaginal rugae) at lower end – Mucosal folds form ____________ across vaginal opening 12  The Vagina 3 Vaginal epithelium – Undergoes metaplasia: transformation from one tissue type to another Childhood: simple cuboidal Puberty: estrogens transform it to _____________ – Bacteria ferment glycogen producing acidic pH in vagina to inhibit growth of pathogens 13  The External Genitalia 1 External genitalia are collectively called the ________ or pudendum – Mons pubis: mound of fat over pubic symphysis bearing most of the pubic hair – Labia majora: pair of thick folds of skin and adipose tissue inferior to the mons – Labia minora: thin, hairless folds medial to labia majora Space between forms vestibule which contains urethral and vaginal openings Anterior margins of labia minora join to form hood-like prepuce over clitoris 14  The External Genitalia 2 Clitoris: _______________________, sensory organ – Primary center for sexual stimulation – Glans, body, and crura Vestibular bulbs: erectile tissue deep to labia majora – Bracket the vagina Greater and lesser vestibular and paraurethral glands open into vestibule for lubrication 15  The Breasts and Mammary Glands 1 Breast — mound of tissue overlying pectoralis major – Enlarges at puberty and remains so for life – Most of the time it contains very little mammary gland Mammary gland — develops within the breast during pregnancy – Remains active in the lactating breast – Atrophies when a woman ceases to nurse 16  The Breasts and Mammary Glands 2 Two principal regions of the breast – Body: conical to pendulous, with nipple at its apex – Axillary tail: extension toward armpit Lymphatics in axillary tail are important as a route for breast cancer metastasis Nipple surrounded by circular colored zone, called the _______________ – Capillaries and nerves close to skin surface: more sensitive – Sensory nerve fibers of areola trigger a milk ejection reflex when an infant nurses 17  The Breasts and Mammary Glands 3 – Areolar glands (Montgomery Glands): intermediate between sweat glands and mammary glands Secretions protect the nipple from chapping and cracking during nursing – Smooth muscle fibers in dermis of areola that contract in response to cold, touch, and sexual arousal, wrinkling the skin and erecting the nipple 18  The Breasts and Mammary Glands 4 The nonlactating breast consists mostly of adipose and collagenous tissue – Breast size determined by amount of adipose tissue Suspensory (Coopers) ligaments attach breast to dermis of overlying skin and fascia of the pectoralis major 19  The Breasts and Mammary Glands 5 Ducts branch through fibrous stroma and converge on the nipple – Mammary gland develops during pregnancy – 15 to 20 lobes around the nipple – Lactiferous duct drains each lobe Dilates to form lactiferous sinus which opens into nipple – Ducts ends in acini (sacs) Acini are surrounded by ____________________ cells 20  Puberty 1 Puberty begins at age 8 to 10 for most girls in United States Triggered by rising levels of GnRH which stimulates anterior pituitary to secrete FSH and LH FSH stimulates ovarian follicles and they begin to secrete estrogen, progesterone, inhibin, and a small amount of androgen Estrogens are feminizing hormones with widespread effects on the body – __________________ (most abundant), estriol, and estrone 21  Puberty 2 _________________ —first menstrual period – Requires at least 17% body fat in teenager Improved nutrition has lowered age of onset to age 12 Leptin stimulates gonadotropin secretion If body fat and leptin levels drop too low, gonadotropin secretion declines and menstrual cycle might cease – Menstruation ceases when body fat drops below 22% in adult woman First few menstrual cycles are anovulatory (no egg ovulated) Girls begin ovulating regularly about a year after they begin menstruating 22  Puberty 3 Estradiol stimulates many changes in puberty – Stimulates vaginal metaplasia – Stimulates growth of ovaries and secondary sex organs – Stimulates growth hormone secretion Increase in height and widening of pelvis – Stimulates fat deposition (breast, hips, etc…) – Thickens skin But girls’ skin is still thinner, softer, and warmer than boys _________________ – Primarily acts on the uterus preparing it for possible pregnancy in the second half of the menstrual cycle 23  Puberty 4 Estrogens and progesterone suppress FSH and LH secretion through negative feedback Inhibin selectively suppresses FSH secretion Hormone secretion is distinctly cyclic and the hormones are secreted in sequence 24  Oogenesis and the Sexual Cycle Reproductive cycle —sequence of events from fertilization to giving birth and returning to fertility Sexual cycle —events that recur every month when pregnancy does not intervene – Consists of two interrelated cycles controlled by shifting patterns of hormone secretion Ovarian cycle —events in ovaries Menstrual cycle —parallel changes in uterus 25  Oogenesis 1 Oogenesis —egg production – Produces haploid gametes by means of meiosis – Distinctly cyclic event that normally releases one egg each month – Accompanied by cyclic changes in hormone secretion – Cyclic changes in histological structure of the ovaries and uterus Uterine changes result in monthly menstrual flow 26  Oogenesis 2 Embryonic development of ovary – Transform into primary oocytes: early meiosis I – Most degenerate (atresia) by the time the girl is born – ____________________: any stage from the primary oocyte to the time of fertilization – By puberty, 200,000 oocytes remain Lifetime supply—probably will ovulate only 480 times 27  Oogenesis 3 Egg development resumes in adolescence – FSH stimulates monthly cohorts of about 24 oocytes to complete meiosis I – Each oocyte divides into two haploid daughter cells of __________ size and different destinies Important to produce an egg with as much cytoplasm as possible – Secondary oocyte: large daughter cell that is the product of meiosis I – First polar body: smaller one that ultimately disintegrates A means of discarding the extra set of haploid chromosomes 28  Oogenesis 4 – Secondary oocyte proceeds as far as metaphase II Arrests until after ovulation If not fertilized, it dies and never finishes meiosis If fertilized, it completes meiosis II and casts off a second polar body – Chromosomes of the large remaining egg unite with those of the sperm 29  The Sexual Cycle 1 Sexual cycle _______________________, varies from 20 to 45 days Hormones of hypothalamus regulate pituitary gland Pituitary hormones regulate the ovaries Ovaries secrete hormones that regulate the uterus Basic hierarchy of hormonal control – Hypothalamus→ pituitary → ovaries → uterus Ovaries exert feedback control over hypothalamus and pituitary 30  The Sexual Cycle 2 Cycle begins with 2-week follicular phase – Menstruation occurs during first 3 to 5 days of cycle – Uterus replaces lost tissue by mitosis and cohort of follicles grow – Ovulation around day 14: remainder of that follicle becomes corpus luteum Next 2 weeks: luteal phase – _________________ stimulates endometrial secretion and thickening – If pregnancy does not occur, endometrium breaks down in the last 2 days – Menstruation begins and the cycle starts over 31  The Ovarian Cycle 1 Ovarian cycle —three principal steps 1. Follicular phase 2. Ovulation 3. Luteal phase This cycle reflects what happens in the ovaries and their relationship to the hypothalamus and pituitary 32  The Ovarian Cycle 2 Follicular phase extends from beginning of menstruation until ovulation (Days 1-14) – Includes preovulatory phase: from end of menstruation until ovulation – Most variable part of cycle; seldom possible to predict date of ovulation – FSH stimulates follicles to grow and secrete estradiol – Dominant follicle becomes increasingly sensitive to FSH, LH, and estradiol Dominant follicle has rich blood supply and large number of FSH receptors, so it becomes preovulatory follicle Other antral follicles degenerate (atresia) Ovary also contains follicles at earlier stages for maturation in future cycles 33  The Ovarian Cycle 3 Ovulation —rupture of the mature follicle and release of its egg and attendant cells – Typically around day 14 Estradiol stimulates a surge of LH and a lesser spike of FSH by anterior pituitary – LH induces several events Primary oocyte completes meiosis I (producing secondary oocyte and first polar body) Follicular fluid builds rapidly and follicle swells (resembles blister on ovary) Ovulation 34  The Ovarian Cycle 4 Uterine tube prepares to catch oocyte – It swells with edema Its fimbriae envelop and caress the ovary in synchrony with the woman’s heartbeat Cilia create gentle current in nearby peritoneal fluid 35  Signs of Ovulation Couples attempting to conceive a child (or avoid pregnancy) may wish to know when ovulation occurs – Cervical mucus becomes thinner and more stretchy (egg white) – Resting body temperature rises 0.4° to 0.6°F – Mittelschmerz Pains — twinges of pain at time of ovulation Best time for conception – Within ________________ after the cervical mucus changes and the basal temperature rises 36  The Ovarian Cycle 5 Luteal (postovulatory) phase —day 15 to day 28, from just after ovulation to onset of menstruation If pregnancy does not occur, events happen as follows: – When follicle ruptures Granulosa and theca interna cells multiply and fill space – Ovulated follicle has now become the ____________________ Named for yellow lipid that accumulates in theca interna cells, now called lutein cells 37  The Ovarian Cycle 6 Transformation from ruptured follicle to corpus luteum is regulated by LH – LH stimulates corpus luteum to grow and secrete rising levels of estradiol and progesterone – 10-fold increase in progesterone is most important aspect of luteal phase Progesterone has a crucial role in preparing the _____________ for possibility of pregnancy LH and FSH secretion declines over the rest of the cycle 38  The Ovarian Cycle 7 – High levels of estradiol and progesterone, along with inhibin from the corpus luteum, have a negative feedback effect on the pituitary – Corpus luteum begins process of involution (shrinkage) Beginning about day 22 (8 days after ovulation) By day 26 involution is complete and what was corpus luteum becomes _____________________ — small scar With diminishing ovarian steroid secretion, FSH levels rise, ripening a new cohort of follicles 39  The Ovarian Cycle 8 – Ovulation occurs in _____ ovary per cycle with the two ovaries usually alternating from month to month – Ovulated oocyte began ripening 290 days earlier and began development before birth 40  The Menstrual Cycle 1 Menstrual cycle —consists of a buildup of endometrium during most of the sexual cycle, followed by its breakdown and vaginal discharge – Divided into four phases: proliferative phase, secretory phase, premenstrual phase, and menstrual phase – First day of noticeable vaginal discharge is defined as ___________ of the sexual cycle Menstrual phase average: 5 days 41  The Menstrual Cycle 2 Proliferative phase —rebuilding of functional layer of endometrium that was lost in last menstruation – At day 5 of menstruation, the endometrium is about 0.5 mm thick and consists only of basal layer – As new cohort of follicles develops, they secrete more estrogen – Estrogen stimulates mitosis in basal layer and regrowth of blood vessels to regenerate the functional layer – By day 14, endometrium is 2 to 3 mm thick – Estrogen also stimulates endometrial cells to produce progesterone receptors 42  The Menstrual Cycle 3 Secretory phase —endometrium thickens more in response to progesterone from corpus luteum – Day 15 to day 26 – Thickening due to secretion and fluid accumulation rather than mitosis – Endometrial glands secrete glycogen – Glands grow wider, longer, and more coiled – Endometrium 5 to 6 mm thick – Soft, wet, nutritious bed available for embryonic development 43  The Menstrual Cycle 4 Premenstrual phase: period of endometrial degeneration – Last 2 days of the cycle – Corpus luteum atrophies and progesterone levels fall – Brings about tissue necrosis and menstrual cramps – Necrotic endometrium mixes with blood and serous fluid: menstrual fluid 44  The Menstrual Cycle 5 Menstrual phase (menses) —discharge of menstrual fluid from the vagina First day of discharge is day 1 of the new cycle Average woman expels about 40 mL of blood and 35 mL of serous fluid over a 5-day period Contains ___________________ so it does not clot 45  Female Sexual Response Divided intercourse into four recognizable phases – Excitement – Plateau – Orgasm – Resolution Sexual intercourse is also known as coitus, coition, or ______________ 46  Excitement and Plateau 1 Excitement and plateau – Labia minora become congested with blood and often ________________labia majora – Labia majora become reddened and enlarged Then flatten and spread away from vaginal orifice – Vaginal transudate: serous fluid that seeps through the walls of the canal – Greater vestibular gland secretions moisten the vestibule and provide 47 lubrication  Excitement and Plateau 2 Lower one-third of vagina constricts: orgasmic platform – Narrower canal and vaginal rugae enhance stimulation and help induce orgasm in both partners Upper end of vagina dilates (becomes cavernous) Tenting effect: uterus stands nearly vertical, where normally it tilts forward over the bladder Breasts swell and nipples become erect Erectile clitoris is primary focus of sexual stimulation 48  Orgasm 1 Late in plateau phase, many women experience involuntary pelvic thrusts, followed by 1 to 2 sec of “suspension” or “stillness” preceding orgasm Orgasm: intense sensation spreading from clitoris through the pelvis – Sometimes with pelvic throbbing and a spreading sense of warmth – Pelvic platform gives three to five strong contractions about 0.8 sec apart – Cervix plunges spasmodically into vagina 49  Orgasm 2 Uterus exhibits peristaltic contraction Anal and urethral sphincters constrict Paraurethral glands (Skene’s Gland) (homologous to prostate) sometimes expel copious fluid similar to prostatic fluid (________________________________) Sometimes women experience reddish, rash-like flush on the lower abdomen, chest, neck, and face Not needed for conception. Increases amount of sperm which enters uterus. Tachycardia, hyperventilation 50  Resolution During resolution, the uterus drops forward to its resting position Orgasmic platform quickly relaxes – Rest of vagina returns more slowly to normal dimensions Flush disappears quickly Areolae and nipples undergo rapid detumescence – Breasts may take 5 to 10 minutes to return to normal size Postorgasmic perspiration Women do not have refractory period – May quickly experience additional orgasms STOP 51  Senescence of the Female Reproductive System Abrupt changes due to menopause Ovarian follicles used up, gametogenesis ceases, and ovaries cease production of sex steroids – ______________, genital atrophy, and reduced libido Elevated risk of osteoporosis and atherosclerosis 52  Climacteric and Menopause 1 Climacteric —midlife change in hormone secretion – Accompanied by ________________: cessation of menstruation Female born with about 2 million eggs, climacteric begins when there are about 1,000 follicles left – Follicles less responsive to gonadotropins – secrete less estrogen and progesterone – Uterus, vagina, and breast atrophy – Skin becomes thinner – Bone mass declines, increasing risk of osteoporosis – Blood vessels constrict and dilate in response to shifting hormone balances Dilations may produce hot flashes: spreading sense of heat from abdomen to thorax, neck, and face 53  Climacteric and Menopause 2 Menopause —cessation of menstrual cycles – Usually occurs between ages of 45 and 55 – Age of menopause has increased in last century – Menopouse considered complete when there has been no menstruation for ______________ 54  Fertility of Aging Females 1 Peak fertility is during early 20’s. As females age there is a dramatic decline is the ability to _______________ at age 35. Dramatic increase in birth doi:10.1093/humupd/8.2.141 defects beginning at age 40 Non-Growing Follicle Age of Women When She % Who Will Not Have Live Abundance Starts To Try To Conceive Birth (Menkin-Larson, 1986) 20 4 25 7 30 12 35 22 doi:10.1371/journal.pone.0008772 40 46 55  Fertility of Aging Females 2 Oldest woman to conceive (w/o medical assistance) and give birth. – Xinju Tian, from China, age 65, gave birth during October 2019 Oldest woman to conceive (w/ medical assistance) and give birth. – Mangayamma Yaramati, from India, age 74, gave birth during September 2019 56 STOP