chapter 28-cut down
Introduction
The female reproductive system serves more purposes than the male system:
Produces and delivers gametes.
Provides nutrition and a safe harbor for fetal development.
Gives birth.
Nourishes the infant.
The female system is more cyclic, secreting hormones in a more complex sequence than the relatively steady secretion in males.
Sexual Differentiation
The two sexes are indistinguishable for the first 8 to 10 weeks of development.
The female reproductive tract develops from the paramesonephric ducts due to the absence of testosterone and müllerian-inhibiting factor (MIF).
Without testosterone:
Mesonephric ducts degenerate.
The genital tubercle becomes the glans clitoris.
Urogenital folds become the labia minora.
Labioscrotal folds develop into the labia majora.
Without MIF, paramesonephric ducts develop into the uterine tubes, uterus, and vagina.
Reproductive Anatomy
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.
External Genitalia (Vulva/Pudendum)
Includes the mons pubis, labium majus, perineum, labium minus, vaginal orifice, vestibule, clitoris, vestibular bulbs, and greater vestibular glands.
The Ovaries
Female gonads that produce egg cells (ova) and sex hormones.
Almond-shaped and nestled in the ovarian fossa, a depression in the posterior pelvic wall.
Tunica albuginea capsule, similar to that on testes.
Outer cortex where germ cells develop.
Inner medulla occupied by major arteries and veins.
Lacks ducts; instead, each egg develops in its own fluid-filled follicle.
Ovulation: Bursting of the follicle and releasing the egg.
Ovarian ligaments attach the ovary to the uterus, and suspensory ligaments attach it to the pelvic wall, containing the ovarian artery, vein, and nerves.
Anchored to the broad ligament by the mesovarium.
The ovary receives blood from the ovarian branch of the uterine artery and the ovarian artery, equivalent to the testicular artery in the male.
Ovarian and uterine arteries anastomose along the margin of the ovary, giving off multiple small arteries that enter the ovary.
Ovarian veins, lymphatics, and nerves also travel through the suspensory ligaments.
Structure includes the oocyte, medulla, cortex, suspensory ligament and blood vessels, mature follicle, secondary follicle, primary follicles, primordial follicles, ovarian ligament, tunica albuginea, corpus albicans, corpus luteum, and fimbriae of the uterine tube.
The Uterine Tubes
Also known as oviducts or fallopian tubes.
Canal about 10 cm long from the ovary to the uterus.
Muscular tube lined with ciliated cells, highly folded into longitudinal ridges.
Major portions:
Infundibulum: Flared, trumpet-shaped distal (ovarian) end.
Fimbriae: Feathery projections on the infundibulum.
Ampulla: Middle and longest part.
Isthmus: Narrower end toward the uterus.
Mesosalpinx: The superior portion of the broad ligament that enfolds the uterine tube.
The Uterus
Thick muscular chamber that opens into the roof of the vagina.
Usually tilts forward over the urinary bladder.
Harbors the fetus, provides a source of nutrition, and expels the fetus at the end of its development.
Pear-shaped organ with:
Fundus: Broad superior curvature.
Body (corpus): Middle portion.
Cervix: Cylindrical inferior end.
Lumen is roughly triangular; upper corners are openings to the uterine tube, lower apex is the internal os.
Not a hollow cavity, but a potential space in the nonpregnant uterus.
The cervical canal connects the lumen to the vagina.
Internal os: Superior opening of the canal into the body of the uterus.
External os: Inferior opening of the canal into the vagina.
Cervical glands secrete mucus, preventing the spread of microorganisms from the vagina to the uterus.
PAP Smears and Cervical Cancer
Cervical cancer is common among women ages 30 to 50.
Risk factors: Smoking, early-age sexual activity, STDs, and human papillomavirus.
Usually begins in the epithelial cells of the lower cervix.
Early detection by PAP smear is the best protection against cervical cancer.
Cells are removed from the cervix and vagina and microscopically examined.
Three grades of cervical intraepithelial neoplasia:
Class I: Mild dysplasia.
Class II: Requires a biopsy.
Class III: May require radiation therapy or hysterectomy.
The Uterus
Perimetrium: External serosa layer.
Myometrium: Middle muscular layer; constitutes most of the uterine wall. Composed mainly of smooth muscle. Produces labor contractions and expels the fetus.
Endometrium: Inner mucosa with simple columnar epithelium, compound tubular glands, and a stroma populated with leukocytes and macrophages.
Stratum functionalis: Superficial half, shed each menstrual period.
Stratum basalis: Deep layer, stays behind and regenerates a new stratum functionalis with each menstrual cycle.
During pregnancy, the endometrium is the site of attachment of the embryo and forms the maternal part of the placenta.
Supported by the muscular floor of the pelvic outlet and folds of the peritoneum that form ligaments around the organ.
Broad ligament: Two parts—mesosalpinx and mesometrium.
Cardinal (lateral cervical) ligaments: Supports the cervix and superior part of the vagina, extending to the pelvic wall.
Uterosacral ligaments: Paired and attach the posterior side of the uterus to the sacrum.
Round ligaments: Paired, arise from the anterior surface of the uterus, pass through inguinal canals, and terminate in the labia majora.
Uterine blood supply is important to the menstrual cycle and pregnancy.
The uterine artery arises from each internal iliac artery and gives off several branches that penetrate the myometrium.
The uterine artery leads to arcuate arteries that travel in a circle around the uterus and anastomose with the arcuate artery on the other side.
Spiral arteries penetrate through the myometrium into the endometrium, rhythmically constricting and dilating, causing the mucosa to alternately blanch and flush with blood.
The 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 the rectum and urethra.
The vagina has no glands; transudation lubricates the vagina.
Fornices: Blind-ended spaces formed from the vagina, extending slightly beyond the cervix.
Transverse friction ridges (vaginal rugae) at the lower end.
Mucosal folds form the hymen across the vaginal opening.
Vaginal epithelium:
Childhood: Simple cuboidal.
Puberty: Estrogens transform to stratified squamous.
Bacteria ferment glycogen-rich cells, producing an acidic pH in the vagina—an example of metaplasia.
Antigen-presenting dendritic cells: Route by which HIV from infected semen invades the female body.
The External Genitalia
Collectively called the vulva or pudendum.
Mons pubis: Mound of fat over the pubic symphysis bearing most of the pubic hair.
Labia majora: Pair of thick folds of skin and adipose tissue inferior to the mons.
Pudendal cleft: Slit between the labia majora.
Labia minora: Medial to the labia majora are thin hairless folds.
Vestibule: Space between the labia minora, containing the urethral and vaginal openings.
Anterior margins of the labia minora join to form a hoodlike prepuce over the clitoris.
Clitoris: Erectile, sensory organ with no urinary role; primary center for erotic stimulation.
Glans, body, and crura.
Vestibular bulbs: Erectile tissue deep to the labia majora; cause the vagina to tighten around the penis, enhancing sexual stimulation.
Greater and lesser vestibular and paraurethral glands open into the vestibule for lubrication.
The Female Perineum
The region between the vaginal orifice and the anus.
Includes the prepuce, clitoris, mons pubis, perineal raphe, hymen, labium majus, labium minus, urethral orifice, anus, and vestibular bulb.
The Breasts and Mammary Glands
Breast: Mound of tissue overlying the pectoralis major; enlarges at puberty and remains so for life.
Mammary gland: Develops within the breast during pregnancy and remains active in the lactating breast; atrophies when a woman ceases to nurse.
Two principal regions of the breast:
Body: Conical to pendulous, with the nipple at its apex.
Axillary tail: Extension toward the armpit.
Nipple surrounded by the areola, a circular colored zone; blood capillaries and nerves are closer to the skin surface, making it more sensitive.
Sensory nerve fibers of the areola trigger a milk ejection reflex when an infant nurses.
Areolar glands: Intermediate between sweat glands and mammary glands; secretions protect the nipple from chapping and cracking during nursing.
Smooth muscle fibers in the dermis of the areola contract in response to cold, touch, and sexual arousal, wrinkling the skin and erecting the nipple.
The nonlactating breast consists mostly of adipose and collagenous tissue; breast size determined by the amount of adipose tissue.
Suspensory ligaments attach the breast to the dermis of the overlying skin and the fascia of the pectoralis major.
System of ducts branching through the fibrous stroma and converging on the nipple; mammary gland develops during pregnancy.
15 to 20 lobes around the nipple; lactiferous duct drains each lobe and dilates to form the lactiferous sinus, which opens into the nipple.
Breast Cancer
Occurs in 1 out of 8 American women.
Tumors begin with cells from mammary ducts and may metastasize by mammary and axillary lymphatics.
Signs may include a palpable lump (the tumor), skin puckering, changes in skin texture, and drainage from the nipple.
Most breast cancer is nonhereditary.
Two breast cancer genes were discovered in the 1990s: BRCA1 and BRCA2.
Some stimulated by long periods of fertility and estrogen exposure.
Risk factors: Aging, exposure to ionizing radiation, carcinogenic chemicals, excessive alcohol and fat intake, and smoking.
70% of cases lack identifiable risk factors.
Tumor discovery is usually during breast self-examination (BSE)—monthly for all women.
Mammograms (breast X-rays):
Late 30s: Baseline mammogram.
Ages 40 to 49: Every 2 years.
Over age 50: Yearly.
Treatment:
Lumpectomy: Removal of the tumor only.
Simple mastectomy: Removal of the breast tissue only or breast tissue and some axillary lymph nodes.
Radical mastectomy: Removal of the breast, underlying muscle, fascia, and lymph nodes.
Surgery followed by radiation or chemotherapy.
Breast reconstruction from skin, fat, and muscle from other parts of the body.
Puberty and Menopause
Expected Learning Outcomes:
Name the hormones that regulate female reproductive function and state their roles.
Describe the principal signs of puberty.
Describe the hormonal changes of female climacteric and their effects.
Define and describe menopause, and distinguish menopause from climacteric.
Puberty
Begins at age 8 to 10 for most girls in the United States.
Triggered by rising levels of GnRH, which stimulates the anterior lobe of the pituitary to produce FSH and LH.
FSH stimulates developing 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: estradiol (most abundant), estriol, and estrone.
Thelarche—onset of breast development is the earliest noticeable sign of puberty.
Initial duct and lobule formation: Estrogen, progesterone, and prolactin.
Completion of duct and lobule formation: Glucocorticoids and growth hormone.
Adipose and fibrous tissue complete breast enlargement by age 20.
Pubarche—appearance of pubic and axillary hair, sebaceous glands, and axillary glands.
Androgens from ovaries and adrenal cortex stimulate pubarche and libido.
Menarche—first menstrual period.
Requires at least 17% body fat in a teenager, 22% in an adult.
Leptin stimulates gonadotropin secretion; if body fat and leptin levels drop too low, gonadotropin secretion declines and a female’s menstrual cycle might cease.
The first few menstrual cycles are anovulatory (no egg ovulated).
Girls begin ovulating regularly about a year after they begin menstruating.
Estradiol:
Stimulates vaginal metaplasia.
Stimulates growth of ovaries and secondary sex organs.
Stimulates growth hormone secretion (increase in height and widening of the pelvis).
Responsible for feminine physique because it stimulates the deposition of fat.
Makes a girl’s skin thicker but remains thinner, softer, and warmer than males of the corresponding age.
Progesterone: Primarily acts on the uterus, preparing it for possible pregnancy in the second half of the menstrual cycle.
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.
Climacteric and Menopause
Climacteric—midlife change in hormone secretion, accompanied by menopause: cessation of menstruation.
A female is born with about 2 million eggs; climacteric begins when there are about 1,000 follicles left.
Follicles are less responsive to gonadotropins.
Less estrogen and progesterone secretion.
Uterus, vagina, and breasts atrophy.
Intercourse becomes uncomfortable as the vagina becomes thinner, less distensible, and drier; vaginal infections are more common.
Skin becomes thinner, cholesterol levels rise increasing the risk of cardiovascular disease, and bone mass declines producing increased risk for osteoporosis.
Blood vessels constrict and dilate in response to shifting hormone balances.
Hot flashes: Spreading sense of heat from the abdomen to the thorax, neck, and face; hormone replacement therapy (HRT) may be used to relieve symptoms.
Evolution of Menopause: Older mother would not live long enough to rear an infant to a survivable age; better to become infertile and help rear her grandchildren.
Pleistocene (Ice Age) skeletons show early hominids rarely lived past age 40; menopause may be an artifact of modern nutrition and medicine.
Oogenesis and the Sexual Cycle
Expected Learning Outcomes:
Describe the process of egg production (oogenesis).
Describe changes in the ovarian follicles (folliculogenesis) in relation to oogenesis.
Describe the hormonal events that regulate the ovarian cycle.
Describe how the uterus changes during the menstrual cycle.
Construct a chart of the phases of the monthly sexual cycle showing the hormonal, ovarian, and uterine events of each phase.
Reproductive cycle—sequence of events from fertilization to giving birth.
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 the uterus.
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 and cyclic changes in histological structure of the ovaries and uterus.
Uterine changes result in monthly menstrual flow.
Embryonic development of ovary:
Female germ cells arise from the yolk sac, colonizing the gonadal ridges in the first 5 to 6 weeks of development, differentiating into oogonia and multiplying until the fifth month (5 to 6 million in number).
Transform into primary oocytes.
Most degenerate (atresia) by the time the girl is born.
Egg, or ovum: Any stage from the primary oocyte to the time of fertilization.
By puberty, 400,000 oocytes remain—lifetime supply, probably will ovulate 480 times.
Egg development resumes in adolescence; FSH stimulates monthly cohorts of oocytes to complete meiosis I.
Each oocyte divides into two haploid daughter cells of unequal size and different destinies.
Secondary oocyte: Large daughter cell that is the product of meiosis I.
First polar body: Smaller one that sometimes undergoes meiosis II but ultimately disintegrates; merely a means of discarding the extra set of haploid chromosomes.
The secondary oocyte proceeds as far as metaphase II and 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.
Folliculogenesis
Development of the follicles around the egg that undergoes oogenesis.
Primordial follicles consist of a primary oocyte in early meiosis, surrounded by a single layer of squamous follicular cells, connected to the oocyte by fine cytoplasmic
Processes for passage of nutrients and chemical signals, concentrated in the cortex of the ovary.
Most wait 13 to 50 years before they develop further; the adult ovary has 90% to 95% primordial follicles.
Primary follicles have larger oocytes and follicular cells that still form a single layer.
Secondary follicles have still larger oocytes and follicular cells now stratified (granulosa cells).
Zona pellucida—layer of glycoprotein gel secreted by granulosa cells around the oocyte.
Theca folliculi—connective tissue around the granulosa cells condenses to form a fibrous husk.
Tertiary follicles
Granulosa cells begin secreting follicular fluid that accumulates in little pools in the follicular wall. This defines tertiary follicles.
As they enlarge, the pools merge, forming a single fluid-filled cavity, the antrum.
Antral follicles—tertiary and mature follicles.
Preantral follicles—earlier stages of the follicles.
Cumulus oophorus—a mound of granulosa cells on one side of the antrum that covers the oocyte and secures it to the follicular wall.
Corona radiata—innermost layer of cells in the cumulus surrounding the zona pellucida and the oocyte, serving as a protective barrier.
Theca folliculi continues to differentiate, forming two layers:
Theca externa: Outer fibrous capsule rich in blood vessels.
Theca interna: Inner cellular, hormone-secreting layer producing androgens (androstenedione and testosterone), and granulosa cells convert them to estradiol.
Mature (Graafian) follicles: Normally only one follicle from each month’s cohort becomes a mature follicle destined to ovulate; the remainder degenerate.
The Sexual Cycle
Averages 28 days, varies from 20 to 45 days.
Hormones of the hypothalamus regulate the 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 negative feedback control over hypothalamus and pituitary.
Cycle begins with a 2-week follicular phase; menstruation occurs during the first 3 to 5 days of the cycle; the uterus replaces lost tissue by mitosis, and a cohort of follicles grows.
Ovulation around day 14: The remainder of the follicle becomes the corpus luteum.
Next 2 weeks: Luteal phase, during which the corpus luteum stimulates endometrial secretion and thickening.
If pregnancy does not occur, the endometrium breaks down in the last 2 days; menstruation begins, and the cycle starts over.
The Ovarian Cycle
Three principal steps: Follicular phase, ovulation, and luteal phase.
The cycle reflects what happens in the ovaries and their relationship to the hypothalamus and pituitary; much remains unknown about the timing of folliculogenesis.
Follicular phase extends from the beginning of menstruation until ovulation (day 1 to day 14 of an average cycle).
Preovulatory phase: From the end of menstruation until ovulation; most variable part of the cycle; seldom possible to reliably predict the date of ovulation.
Preparation begins almost 2 months earlier; shortly after ovulation, a new cohort of preantral follicles descends from the cortex deeper into the ovary and begins to grow, each developing an antrum.
Selection window of 5 days in which one of them is selected as the dominant follicle to mature and ultimately ovulate in the next cycle.
FSH stimulates continued growth of the cohort, but the dominant follicle above all; FSH stimulates the granulosa cells of the antral follicles to secrete estradiol.
The dominant follicle becomes more sensitive to FSH and LH, grows, and becomes a mature (Graafian) follicle, while others degenerate.
Ovulation: The rupture of the mature follicle and the release of its egg and attendant cells, typically around day 14.
Estradiol stimulates a surge of LH and a lesser spike of FSH by the anterior pituitary.
LH induces several events:
Primary oocyte completes meiosis I, producing a secondary oocyte and first polar body.
Follicular fluid builds rapidly, and the follicle swells; looks like a blister on the ovary surface.
Follicular wall weakened by inflammation and proteolytic enzymes; the mature follicle approaches rupture.
Ovulation takes only 2 to 3 minutes; a nipplelike stigma appears on the ovary surface over the follicle, which seeps follicular fluid for 1 to 2 minutes.
The follicle bursts, and remaining fluid oozes out, carrying the secondary oocyte and cumulus oophorus; normally swept up by the ciliary current and taken into the uterine tube.
The uterine tube prepares to catch the oocyte when it emerges; it swells with edema, and its fimbriae envelop and caress the ovary in synchrony with the woman’s heartbeat.
Cilia create a gentle current in the nearby peritoneal fluid.
Couples attempting to conceive a child or avoid pregnancy need to be able to tell when ovulation occurs.
Cervical mucus becomes thinner and more stretchy.
Resting body temperature rises ° to °F (best measured first thing in the morning before arising from bed).
LH surge occurs about 24 hours prior to ovulation; detected with a home testing kit.
Twinges of ovarian pain (mittelschmerz) last from a few hours to a day or so at the time of ovulation.
Best time for conception is within 24 hours after the cervical mucus changes and the basal temperature rises.
Luteal (postovulatory) phase—day 15 to day 28, from just after ovulation to the onset of menstruation; if pregnancy does not occur, events happen as follows:
When the follicle ruptures, it collapses and bleeds into the antrum; clotted blood is slowly absorbed.
Granulosa and theca interna cells multiply and fill the antrum; a dense bed of capillaries grows amid them.
The ovulated follicle has now become the corpus luteum, named for a yellow lipid that accumulates in the theca interna cells (now called lutein cells).
Transformation from ruptured follicle to corpus luteum is regulated by LH, which stimulates the corpus luteum to continue to grow and secrete rising levels of estradiol and progesterone.
A 10-fold increase in progesterone is the most important aspect of the luteal phase, crucial for preparing the uterus for the possibility of pregnancy.
LH and FSH secretion declines over the rest of the cycle.
High levels of estradiol and progesterone, along with inhibin from the corpus luteum, have a negative feedback effect on the pituitary.
The corpus luteum begins the process of involution (shrinkage) beginning about day 22 (8 days after ovulation).
By day 26, involution is complete, and it becomes inactive bit of scar tissue, the corpus albicans; with diminishing ovarian steroid secretion, FSH levels rise ripening a new cohort of follicles.
Ovaries usually alternate from month to month.
The Menstrual Cycle
Consists of a buildup of the endometrium during most of the sexual cycle, followed by its breakdown and vaginal discharge; divided into four phases:
Proliferative phase.
Secretory phase.
Premenstrual phase.
Menstrual phase.
The first day of noticeable vaginal discharge is defined as day 1 of the sexual cycle; average: 5 days.
Proliferative phase: The layer of endometrial tissue (stratum functionalis) lost in the last menstruation is rebuilt; at day 5 of menstruation, the endometrium is about 0.5 mm thick and consists only of the stratum basalis.
Estrogen stimulates mitosis in the stratum basalis and the prolific regrowth of blood vessels, regenerating the functionalis; by day 14, it is 2 to 3 mm thick.
Estrogen also stimulates endometrial cells to produce progesterone receptors.
Secretory phase: The endometrium thickens still more in response to progesterone from the corpus luteum (day 15 to day 26); secretion and fluid accumulation rather than mitosis.
Progesterone stimulates endometrial glands to secrete glycogen; glands grow wider, longer, and more coiled; the endometrium is 5 to 6 mm thick—a soft, wet, nutritious bed available for embryonic development.
Premenstrual phase: Period of endometrial degeneration during the last 2 days of the cycle; the corpus luteum atrophies, and progesterone levels fall sharply, triggering spasmodic contractions of spiral arteries, causing endometrial ischemia (interrupted blood flow), bringing about tissue necrosis and menstrual cramps.
Pools of blood accumulate in the stratum functionalis; necrotic endometrium mixes with blood and serous fluid: Menstrual fluid.
Menstrual phase—discharge of menstrual fluid from the vagina (menses); the first day of discharge is day 1 of the new cycle; the average woman expels about 40 mL of blood and 35 mL of serous fluid over a 5-day period; contains fibrinolysin so it does not clot.
Female Sexual Response
Expected Learning Outcomes:
Describe the female sexual response at each phase of intercourse.
Compare and contrast the female and male responses.
Excitement and Plateau
Labia minora becomes congested and often protrudes beyond the labia majora; labia majora becomes reddened and enlarged but then flattens and spreads away from the vaginal orifice.
Vaginal transudate: Serous fluid that seeps through the walls of the canal.
Greater vestibular gland secretion moistens the vestibule and provides lubrication.
Lower one-third of the vagina constricts: Orgasmic platform, which enhances stimulation and helps induce orgasm in both partners.
Tenting effect: The uterus stands nearly vertical.
Breasts swell, and nipples become erect.
Stimulation of the erect clitoris brings about erotic stimulation through thrusting of the penis and pressure between the pubic symphyses of the partners.
Orgasm
Late in the plateau phase, many women experience involuntary pelvic thrusts, followed by 1 to 2 seconds 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 seconds apart; the cervix plunges spasmodically into the vagina and pool of semen.
The uterus exhibits peristaltic contractions, and anal and urethral sphincters constrict.
Paraurethral glands (homologous to the prostate) sometimes expel copious fluid similar to prostatic fluid (female ejaculation).
Tachycardia, hyperventilation.
Sometimes women experience a reddish, rashlike flush that appears on the lower abdomen, chest, neck, and face.
Resolution
During resolution, the uterus drops forward to its resting position.
The Orgasmic platform quickly relaxes, and the rest of the vagina returns more slowly to its normal dimensions.
The flush disappears quickly, and the areolae and nipples undergo rapid detumescence; it may take 5 to 10 minutes for the breasts to return to normal size.
Postorgasmic outbreak of perspiration.
Women do not have a refractory period and may quickly experience additional orgasms.
Pregnancy and Childbirth
Expected Learning Outcomes:
List the major hormones that regulate pregnancy and explain their roles.
Describe a woman’s bodily adaptations to pregnancy.
Identify the physical and chemical stimuli that increase uterine contractility in late pregnancy.
Describe the mechanisms of labor contractions.
Name and describe the three stages of labor.
Describe the physiological changes that occur in a woman during the weeks following childbirth.
Pregnancy from a maternal standpoint includes adjustments of the woman’s body to pregnancy and the mechanism of childbirth.
Gestation (pregnancy) lasts an average of 266 days from conception to childbirth; gestational calendar measured from the first day of the woman’s last menstrual period (LMP), with birth predicted 280 days (40 weeks) from LMP.
Term: Duration of pregnancy; trimester: The three 3-month intervals in the term.
Prenatal Development:
Conceptus—all products of conception: the embryo or fetus, the placenta, and associated membranes.
Blastocyst: The developing individual is a hollow ball for the first 2 weeks.
Embryo: From day 16 through 8 weeks.
Fetus: From beginning of week 9 to birth; attached by way of an umbilical cord to a disc-shaped placenta.
Neonate: Newborn to 6 weeks.
Provides fetal nutrition and waste disposal; secretes hormones that regulate pregnancy, mammary development, and fetal development.
Hormones of Pregnancy
Hormones with the strongest influence on pregnancy are estrogens, progesterone, human chorionic gonadotropin, and human chorionic somatomammotropin; all primarily secreted by the placenta.
The corpus luteum is an important source for the first several weeks(If corpus luteum removed before 7 weeks, abortion).
From week 7 to week 17, the corpus luteum degenerates, and the placenta takes over its endocrine function.
Human chorionic gonadotropin (HCG) is secreted by the blastocyst and placenta and is detectable in urine 8 to 9 days after conception with home pregnancy test kits; it stimulates the growth of the corpus luteum, which secretes increasing amounts of progesterone and estrogen.
Estrogens: Increase to 30 times normal by the end of gestation and is derived from the corpus luteum for the first 12 weeks until the placenta takes over gradually during weeks 7 to 17; It causes tissue growth in the fetus and the mother.
The mother’s uterus and external genitalia enlarge; mammary ducts grow, and breasts increase to nearly twice normal size; it relaxes the pubic symphysis and widens the pelvis.
Progesterone secreted by the placenta and corpus luteum; it suppresses secretion of FSH and LH, preventing follicular development during pregnancy.
It suppresses uterine contractions, prevents menstruation, and thickens the endometrium, promotes of decidual cells of the endometrium on which the blastocyst feeds, and stimulates the development of acini in the breast in another step toward lactation.
Human chorionic somatomammotropin (HCS): Placenta begins its secretion about week 5 and increases steadily until term in proportion to placental size; its effects seem similar to growth hormone but weaker; it seems to reduce the mother’s insulin sensitivity and glucose usage, leaving more for the fetus.
A woman’s pituitary gland grows about 50% larger during pregnancy, producing markedly elevated levels of thyrotropin, prolactin, and ACTH.
The thyroid gland becomes 50% larger under the influence of HCG, pituitary thyrotropin, and human chorionic thyrotropin from the placenta, increasing the metabolic rate of the mother and fetus.
Parathyroid glands enlarge and increase osteoclast activity.
ACTH stimulates glucocorticoid secretion, which primarily serves to mobilize amino acids for fetal protein synthesis.
Aldosterone secretion rises, promoting fluid retention and increasing the mother’s blood volume.
Relaxin, secreted by the corpus luteum and placenta, synergizes progesterone in stimulating the multiplication of decidual cells and promotes the growth of blood vessels in the pregnant uterus.
Adjustments to Pregnancy
Digestive system:
Morning sickness: Nausea, especially arising from bed in the first few months of gestation, of unknown cause.
Constipation and heartburn due to reduced intestinal motility and pressure on the stomach, causing reflux of gastric contents into the esophagus.
Metabolism:
Basal metabolic rate (BMR): Rises about 15% in the second half of gestation, and the appetite may be strongly stimulated.
Healthy average weight gain: 24 lb.
Nutrition: Placenta stores nutrients in early gestation and releases them in the last trimester; demand is especially high for protein, iron, calcium, and phosphates.
Needs extra iron during late pregnancy or will become anemic.
Vitamin K is given in late pregnancy to promote prothrombin synthesis in the fetus and minimize risk of neonatal hemorrhage, especially in the brain.
Vitamin D supplements help ensure adequate calcium absorption to meet fetal demand.
Folic acid reduces the risk of neurological fetal disorders like spina bifida and anencephaly, and supplements must be started before pregnancy.
Circulatory system:
By full term, the placenta requires 625 mL of blood per minute from the mother, and the mother’s blood volume rises about 30% during pregnancy due to fluid retention and hemopoiesis.
The mother has about 1 to 2 L of extra blood.
The mother’s cardiac output rises 30% to 40% above
More detailed notes
Introduction
The female reproductive system serves several critical functions beyond those of the male reproductive system:
Gamete Production and Delivery: It produces mature female gametes (ova) and delivers them to the site of fertilization, typically the uterine tubes.
Fetal Development: The system provides the necessary environment for the fertilized egg to implant and develop into a fetus, ensuring it receives nutrition and protection throughout gestation.
Childbirth: This system is equipped to facilitate childbirth, allowing for the safe delivery of the infant.
Lactation: The female reproductive system nourishes the infant post-birth through the mammary glands, producing milk.
The hormonal regulation in females is characterized by a more complex cyclic pattern, influenced by fluctuating levels of estrogen and progesterone, compared to the relatively steady secretion levels observed in males.
Sexual Differentiation
The development of sex-specific structures begins early in embryonic development and remains indistinguishable for the first 8 to 10 weeks.
The female reproductive tract arises from the paramesonephric ducts, which develop due to the absence of testosterone and müllerian-inhibiting factor (MIF).
In the absence of testosterone:
The mesonephric ducts regress.
The genital tubercle elongates and forms the glans clitoris.
The urogenital folds develop into the labia minora.
The labioscrotal folds develop into the labia majora.
Moreover, the absence of MIF allows the paramesonephric ducts to evolve into the uterine tubes, uterus, and vagina, establishing the foundation of the female reproductive system.
Reproductive Anatomy
Internal genitalia include the ovaries, uterine tubes, uterus, and vagina, which play essential roles in reproduction.
External genitalia consist of the clitoris, labia majora, and labia minora, which protect the internal structures and play a role in sexual arousal.
These structures are located within the perineum, which is the area between the anus and the reproductive organs.
The primary sex organs are the ovaries, responsible for producing oocytes and hormones. The secondary sex organs encompass the remaining internal and external genitalia essential for reproduction.
External Genitalia (Vulva/Pudendum)
The vulva consists of:
Mons pubis: A fatty tissue mound over the pubic bone, providing cushioning and bearing pubic hair.
Labia majora: Thick, protective folds of skin that are lateral to the vagina and contain fat and sweat glands.
Labia minora: Thinner, hairless folds situated medial to the labia majora, encapsulating the vaginal and urethral openings.
Clitoris: An erectile, sensory organ central to female sexual arousal and response.
Vaginal orifice: The opening to the vagina, leading to the internal reproductive tract.
Vestibular bulbs and glands: Provide lubrication during sexual arousal.
The Ovaries
The ovaries are almond-shaped structures that function as gonads, producing ova and sex hormones such as estrogen and progesterone.
They reside within the ovarian fossa on the posterior pelvic wall, supported by various ligaments including the ovarian and suspensory ligaments that anchor them in place.
The ovaries are covered by a protective tissue known as tunica albuginea.
Oocyte maturation occurs within fluid-filled follicles, with ovulation marking the release of an egg following follicular rupture.
Blood supply is crucial for ovarian function, with the ovarian artery and uterine artery providing necessary nutrients and hormones.
The Uterine Tubes
The uterine tubes (oviducts) are channels connecting the ovaries to the uterus, essential for transporting the ovum post-ovulation and providing the location for fertilization. They measure approximately 10 cm and consist of four parts:
Infundibulum: A flared, trumpet-shaped end near the ovary with fimbriae that help guide the ovum.
Ampulla: The widest and longest section where fertilization often occurs.
Isthmus: The narrower part connected to the uterus.
Mesosalpinx: A portion of the broad ligament that supports the uterine tube.
The Uterus
A muscular chamber which serves multiple roles:
Provides a nutrient-rich environment for embryo and fetal development.
Expels the fetus during childbirth.
Has a pear shape with three main areas: fundus (top), body (main part), and cervix (bottom opening).
Endometrial layers interact with hormonal cycles, thickening and shedding during menstruation.
PAP Smears and Cervical Cancer
Early detection of cervical cancer, prevalent in women aged 30 to 50, is facilitated by PAP smears, which analyze cervical cells for anomalies. Risk factors include:
Smoking
Early sexual activity
History of STDs, particularly human papillomavirus (HPV).
It starts in cervical epithelial cells and can develop into various grades of cervical intraepithelial neoplasia, classified from mild dysplasia (Class I) to advanced requiring surgical intervention (Class III).
The Vagina
The vagina serves as both the birth canal and the reproductive tract, featuring:
Three layers: a fibrous adventitia, muscularis, and mucosa, which adapts in thickness and structure over the course of a woman’s life.
The vagina’s acidic environment is vital for protecting against infections, aided by resident bacteria that ferment glycogen.
The vestibule, or vaginal opening area, features folds called hymen, which may partially cover the opening at birth.
The Female Perineum
The area between the vaginal opening and anus is known as the perineum. It contains multiple structures that support sexual function and childbirth.