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Chapter 28

Lecture Outline

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Female Reproductive System

• Reproductive Anatomy

• Puberty and Menopause

• Oogenesis and the Sexual Cycle

• Female Sexual Response

• Pregnancy and Childbirth

• Lactation

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• Produce and deliver gametes

• Provide nutrition and room for fetal development

• Give birth• Nourish infant

Female Reproductive System

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Sex Differentiation

• Male and female are indistinguishable for first 8 to 10 weeks of development

• Female develops– no testosterone or müllerian-inhibiting factor

• causes degeneration of (male) mesonephric duct

– paramesonephric duct • develops into uterine tubes, uterus and vagina

– genital tubercle becomes clitoris

– urogenital folds develop into labia minora – labioscrotal folds into labia majora

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Ovary

• Produces eggs and hormones– almond-shaped, 3 cm x 1.5 cm x 1 cm– tunica albuginea capsule like on testes– cortex produces gametes; medulla holds vessels

• Each egg develops in its own fluid-filled follicle and is released by ovulation

• Ligaments– attached to uterus by ovarian ligament– attached to pelvic wall by suspensory ligament

• contains ovarian artery, vein and nerves

– anchored to broad ligament by mesovarium

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Anatomy of Ovary

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Secondary Sex Organs

• Internal genitalia– duct system of uterine tubes, uterus,

vagina

• External genitalia– clitoris, labia minora, and labia majora

– occupy perineum

– accessory glands beneath skin provide lubrication

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• 10 cm long, muscular tube lined with ciliated cells

• Major portions– narrow isthmus near uterus– body (ampulla): middle

portion– flares distally into

infundibulum with fimbriae

• Enclosed in superior margin of broad ligament (mesosalpinx)

Uterine (Fallopian) Tubes

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Epithelial Lining of Uterine Tube

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Uterus

• Thick-walled, pear-shaped muscular chamber that opens into vagina and tilts forward over urinary bladder– internal and external os of cervical canal– openings into uterine tubes in two upper corners

• Domed fundus above body of organ

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Reproductive Tract with Ligaments

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Histology of Uterine Wall

• Perimetrium - external serosa layer

• Myometrium - middle muscular layer – 1.25 cm thick in nonpregnant uterus– smooth muscle

• produces labor contractions, expels fetus

• Endometrium– simple columnar epithelium with thick layer

compound tubular glands• stratum functionalis – superficial, shed each period• stratum basalis - deep layer, regenerates a new

stratum functionalis with each menstrual cycle

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Normal/Abnormal PAP Smears

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Vessels of Reproductive Tract

Hormonal changes cause spiral artery vasoconstriction, necrosis of stratum functionalis and menstrual flow

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Ligaments of Reproductive Tract

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Vagina

• 8-10 cm distensible muscular tube– allows for discharge of menstrual fluid, receipt of

penis, semen and birth of baby

• Outer adventitia, middle muscularis and inner mucosa

• Epithelium– child - simple cuboidal– puberty - estrogens transform to stratified squamous

• bacteria ferment glycogen rich cells producing acidic pH

• Tilted posteriorly between rectum and urethra– urethra embedded in its anterior wall

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Vulva (Pudendum)

• Mons pubis - mound of fat over pubic symphysis; covered by pubic hair

• Labia majora - thick folds of skin• Labia minora - medial, thin hairless folds

– form vestibule contains urethral and vaginal openings– form hoodlike prepuce over clitoris

• Clitoris - erectile, sensory organ• Vestibular bulbs - erectile tissue around vagina• Greater and lesser vestibular and paraurethral

glands open into vestibule for lubrication

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Female Perineum Showing Vulva

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Components of Female Perineum

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Breasts

• Overlies pectoralis major– conical body, nipple at apex– axillary tail contains many lymphatic vessels

• Nipple surrounded by areola– dermal blood vessels closer to surface– melanocytes darken during pregnancy– smooth muscle contracts wrinkling skin and erecting

nipple in response to cold, touch and arousal

• Suspensory ligaments from skin, muscle• Nonlactating breast has little glandular tissue

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Anatomy of Lactating Breast

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Anatomy of Lactating Breast

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Sagittal Section of Breast

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Breast Cancer

• 1 out of 8 American women• Tumors begin with cells from mammary ducts

– may metastasize by lymphatics

• Symptoms may include palpable lump, skin puckering, skin texture and drainage from nipple

• Most breast cancer is nonhereditary– some stimulated by estrogen

• Risk factors include – aging, ionizing radiation, carcinogenic chemicals,

alcohol, smoking and fat intake – 70% lack risk factors

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Cancer Screening and Treatment

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Puberty

• Begins at age 9-10 (US)

• Triggered by rising levels of GnRH – stimulates anterior lobe of pituitary to produce

• follicle-stimulating hormone (FSH) • luteinizing hormone (LH)

• Follicles develop and begin to secrete estrogen and progesterone

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Puberty

• Thelarche - development of breasts

• Pubarche - growth of pubic and axillary hair; apocrine and sebaceous glands

• Menarche - first menstrual period– requires at least 17% body fat in teenager,

22% in adult • leptin stimulates gonadotropin secretion• improved nutrition ( body fat) has lowered avg.

age of onset to 12

• Female hormones secreted cyclically and in sequence

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Climacteric• Midlife change in hormone secretion

– due to age related depletion of follicles– occurs with menopause (cessation of

menstruation); average age of 52

• Results– atrophy of uterus, vagina and breasts– skin becomes thinner, bone mass declines,

and risks of cardiovascular disease increase

– hot flashes (sudden dilation of cutaneous arteries) occur several times a day

• HRT = hormone replacement therapy

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Oogensis and Sexual Cycle

• Reproductive cycle - events occurring between fertilization and birth

• Sexual cycle - events recurring every month when pregnancy does not occur– ovarian cycle = events in ovaries– menstrual cycle = parallel changes in uterus

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Oogenesis

• Monthly event produces haploid egg by meiosis• Embryonic development of ovary

– female germ cells arise from yolk sac– differentiate into oogonia, multiply– transform into primary oocytes - early meiosis I– most degenerate (atresia) by childhood– by puberty 400,000 oocytes remain

• FSH stimulates completion of meiosis I, produces secondary oocyte and 1st polar body– proceeds to meiosis II and ceases until fertilization– after fertilization , releases 2nd polar body

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Oogenesis and Follicle Development

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Sexual Cycle

• Averages 28 days, ranges from 20 to 45• Hormone cycle: hierarchy of control

– hypothalamus pituitary ovaries uterus

• Follicular phase (2 weeks) – menstruation occurs during first 3 to 5 days of cycle– uterus replaces lost endometrium and follicles grow

• Luteal phase (2 weeks)– corpus luteum stimulates endometrial thickening– endometrium lost without pregnancy

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Ovarian Cycle - Follicular Phase

• Menstruation (day 1) to ovulation(14) (variable)• Difficult to predict date of ovulation• Contains menstrual and preovulatory phases

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Ovarian Cycle - Preantral Phase

• Discharge of menstrual fluid (days 1-5)• Before follicle develops antrum

– primordial and primary follicles

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Ovarian Cycle - Antral Phase

• Day 6 to 14, one dominant follicle advances to mature (graafian) follicle; secretes estrogen

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Ovarian Cycle - Ovulation

• Mature follicle ruptures, releases oocyte influenced by LH

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Histology of Ovarian Follicles

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Pituitary-Ovarian Axis

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Ovarian Cycle - Luteal Phase

• Corpus luteum - forms from ruptured follicle, under influence of LH; secretes progesterone

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Menstrual Cycle - Proliferative Phase

• Day 6-14 rebuild endometrial tissue – mitosis occurs in stratum basalis– result of estrogen from developing follicles

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• Further thickening of endometrium due to secretion and fluid accumulation -- not mitosis

• Due to progesterone stimulation of glands

Menstrual Cycle - Secretory Phase

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Menstrual Cycle Premenstrual Phase

• Involution of corpus luteum, progesterone falls– spiral arteries constrict causes endometrial ischemia– stratum functionalis sloughs

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Menstrual Cycle - Menstrual Phase

• Blood, serous fluid and endometrial tissue are discharged

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Female Sexual Response

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Pregnancy and Childbirth

• Gestation (pregnancy) – lasts an average of 266 days from conception

to childbirth– gestational calendar measured from first day

of the woman’s last menstrual period (LMP)

• Birth predicted 280 days from LMP– 3 three month intervals called trimesters

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Prenatal Development

• Age based terminology– blastocyst is less than 2 weeks old– embryo is from 2 to 8 weeks old– fetus is 9 weeks to birth– neonate - newborn to 6 weeks

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Hormones of Pregnancy

• HCG (human chorionic gonadotropin)– secreted by trophoblast within 9 days of

conception– prevents involution of corpus luteum

• Estrogens – increases to 30 times normal before birth– corpus luteum is source for first 12 weeks until

placenta takes over– causes uterine, mammary duct and breast

enlargement

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Hormones of Pregnancy

• Progesterone – secreted by placenta and corpus luteum– suppresses secretion of FSH and LH

preventing follicular development– prevents menstruation, thickens endometrium– stimulates development of acini in breast

• HCS (human chorionic somatomammotropin)– secreted from placenta in direct proportion to

its size mother’s glucose usage and release of fatty

acids

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Hormones of Pregnancy

• Aldosterone secretion rises – fluid retention mother’s blood volume

• Endocrine organs– thyroid gland increases 50% in size

BMR of mother

– parathyroid glands enlarge • stimulate osteoclasts to release additional calcium

from mother’s bones

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Hormone Levels and Pregnancy

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Adjustments to Pregnancy

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Adjustments to Pregnancy

• Digestive System – nausea

• first few months

– constipation and heartburn due to intestinal motility • pressure on stomach

• Metabolism– BMR may stimulate appetite

• healthy weight gain - 24 lb.

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Adjustments to Pregnancy

• Nutrition– placenta stores nutrients for 3rd trimester

• protein, iron, calcium, phosphates

– vitamin K• reduces risk of hemorrhages in neonatal brain

– folic acid • prevent neurological disorders

– spina bifida, anencephaly • supplements must be started before pregnancy

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Adjustments to Pregnancy

• Circulatory System– mother’s blood volume and cardiac output -

rises 30% • due to fluid retention and hemopoiesis• by full term, placenta requires 625 mL of

blood/minute

– hemorrhoids and varicose veins • from pressure on large pelvic blood vessels

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Adjustments to Pregnancy

• Respiratory System– minute ventilation about 50%

• demands of fetus, higher maternal metabolic rate

• ventilation adjusted to keep PCO2 lower than normal

– respiratory rate • difficult to breathe deeply

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Adjustments to Pregnancy

• Urinary System– salt and water retention

• due to aldosterone and steroids

– GFR by 50% and output is slightly elevated• mother disposes additional metabolic wastes

frequency of urination • due to bladder compression

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Adjustments to Pregnancy

• Integumentary Systems– stretch marks

• due to dermal stretching

– linea alba may become dark (linea nigra)– temporary chloasma or “mask of pregnancy”

• blotchy darkening of skin over nose and cheeks

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Childbirth - Uterine Contractility

• Parturition – process of giving birth

• by contraction of uterine and abdominal muscles

• Braxton Hicks contractions – throughout gestation– strengthen late in pregnancy - false labor

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Childbirth - Uterine Contractility

• Progesterone inhibits contractions • Estrogen stimulates contractions• Near full term - posterior pituitary releases

more oxytocin, uterus produces more receptors– directly stimulates myometrial contractions– stimulates fetal membranes to produce

prostaglandins - synergists of oxytocin

• Stretching – increases contractility of smooth muscle– role in initiating labor

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Labor Contractions

• Contractions begin 30 minutes apart and eventually occur every 1-3 minutes– periodically relax to blood flow to placenta

and fetus– contractions strongest in fundus and body of

uterus, pushes fetus into cervix

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Labor Contractions

• Self-amplifying cycle of stretch and contraction– positive feedback cycles increase contractions

• cervical stretching oxytocin secretion uterine contraction repeat

• reflex arc from uterus spinal cord abdominal skeletal muscles

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Pain of Labor

• Ischemia of myometrium

• Stretching of cervix, vagina and perineum – episiotomy prevents tearing

• Large fetal head in a narrow pelvic outlet

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Stages of Labor -- Early Dilation

• Widening of cervical canal by effacement (thinning) of cervix to reach 10 cm -- diameter of fetal head

• Rupture of fetal membranes and loss of amniotic fluid

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Stages of Labor -- Late Dilation

Dilation reaches 10 cm in 24 hours or less in primipara (first baby) and in as little as few minutes in multipara

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Stages of Labor -- Expulsion

• Time baby’s head enters vagina until delivery– up to 30 minutes

• Valsalva maneuver helps to expel fetus

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Stages of Labor -- Placental

• Uterine contractions continue causing placental separation

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Crowning (Expulsion Stage)

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Expulsion Stage (cont.)

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Placental Stage

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Puerperium

• First 6 weeks after delivery

• Anatomy and physiology return to normal– involution of uterus

• to pre-gravid weight in 4 weeks• accomplished by autolysis by lysosomal enzymes

– vaginal discharge called lochia

– breastfeeding promotes involution• suppresses estrogen secretion• stimulates oxytocin which causes myometrial

contraction

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Mammary Gland Development

• Lactation – synthesis and ejection of milk from mammary

glands in breast

• Ducts grow and branch – due to high estrogen levels in pregnancy

• Followed by budding and development of acini at the ends of the ducts – due to progesterone

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Colostrum and Milk Synthesis

• Colostrum forms in late pregnancy– similar to breast milk; contains 1/3 less fat,

thinner– first 1 to 3 days after birth– contains IgA protection from gastroenteritis

• Synthesis is promoted by prolactin (from pituitary)– synthesis of hormone begins 5 weeks into

pregnancy, by full term it is 20x normal level– steroid hormones from placenta oppose it until

birth

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Colostrum and Milk Synthesis

• At birth, prolactin secretion drops, but 20 times after nursing– without nursing, milk production stops in 1

week

• 5-10% of women become pregnant while nursing– inhibition of GnRH and reduced ovarian

cycling

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Prolactin and Lactation

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Milk Ejection

• Controlled by a neuroendocrine reflex– infant’s suckling stimulates sensory

receptors in nipple, signaling hypothalamus and posterior pituitary to release oxytocin

– oxytocin stimulates myoepithelial cells

• Myoepithelial cells surround secretory cells in acinus– contract to squeeze milk into duct

• milk flow within 30-60 seconds after suckling begins

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Breast Milk

• Supplies antibodies and colonizes intestine with beneficial bacteria

• Colostrum and milk have a laxative effect that clears intestine of meconium (green, bile-filled fecal material in newborn)

• Nursing woman can produce 1.5L per day

• Cow’s milk not a good substitute– 1/3 less lactose but 3 times as much protein– harder to digest and more nitrogenous waste

(diaper rash)

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Contraceptive Devices