hormonal interactions during the ovarian cycle

Hormonal Interactions During Hormonal Interactions During the Ovarian Cyclethe Ovarian Cycle

Day 1 – GnRH stimulates the release of FSH Day 1 – GnRH stimulates the release of FSH and LHand LH

FSH and LH stimulate follicle growth and FSH and LH stimulate follicle growth and maturation, and low-level estrogen releasematuration, and low-level estrogen release

Rising estrogen levels:Rising estrogen levels: Inhibit the release of FSH and LH Inhibit the release of FSH and LH Prod the pituitary to synthesize and accumulate Prod the pituitary to synthesize and accumulate

these gonadotropinsthese gonadotropins


Estrogen levels increase and high estrogen Estrogen levels increase and high estrogen levels have a positive feedback effect on the levels have a positive feedback effect on the pituitary, causing a sudden surge of LH pituitary, causing a sudden surge of LH


The LH spike stimulates the primary oocyte to The LH spike stimulates the primary oocyte to complete meiosis I, and the secondary oocyte complete meiosis I, and the secondary oocyte continues on to metaphase IIcontinues on to metaphase II

Day 14 – LH triggers ovulationDay 14 – LH triggers ovulation LH transforms the ruptured follicle into a LH transforms the ruptured follicle into a

corpus luteum, which produces inhibin, corpus luteum, which produces inhibin, progesterone, and estrogenprogesterone, and estrogen


These hormones shut off FSH and LH release These hormones shut off FSH and LH release and declining LH ends luteal activityand declining LH ends luteal activity

Days 26-28 – decline of the ovarian hormones Days 26-28 – decline of the ovarian hormones Ends the blockade of FSH and LHEnds the blockade of FSH and LH The cycle starts anewThe cycle starts anew

Feedback Mechanisms in Ovarian Feedback Mechanisms in Ovarian FunctionFunction

Figure 27.21

Uterine (Menstrual) CycleUterine (Menstrual) Cycle Series of cyclic changes that the uterine Series of cyclic changes that the uterine

endometrium goes through each month in endometrium goes through each month in response to ovarian hormones in the bloodresponse to ovarian hormones in the blood

Days 1-5: Menstrual phase – uterus sheds all Days 1-5: Menstrual phase – uterus sheds all but the deepest part of the endometriumbut the deepest part of the endometrium

Days 6-14: Proliferative (preovulatory) phase Days 6-14: Proliferative (preovulatory) phase – endometrium rebuilds itself– endometrium rebuilds itself

Days 15-28: Secretory (postovulatory) phase – Days 15-28: Secretory (postovulatory) phase – endometrium prepares for implantation of the endometrium prepares for implantation of the embryo embryo

MensesMenses If fertilization does not occur, progesterone If fertilization does not occur, progesterone

levels fall, depriving the endometrium of levels fall, depriving the endometrium of hormonal supporthormonal support

Spiral arteries kink and go into spasms and Spiral arteries kink and go into spasms and endometrial cells begin to dieendometrial cells begin to die

The functional layer begins to digest itselfThe functional layer begins to digest itself Spiral arteries constrict one final time then Spiral arteries constrict one final time then

suddenly relax and open widesuddenly relax and open wide The rush of blood fragments weakened The rush of blood fragments weakened

capillary beds and the functional layer sloughscapillary beds and the functional layer sloughs

Extrauterine Effects of Estrogens Extrauterine Effects of Estrogens and Progesteroneand Progesterone

Estrogen levels rise during pubertyEstrogen levels rise during puberty Promote oogenesis and follicle growth in the Promote oogenesis and follicle growth in the

ovaryovary Exert anabolic effects on the female Exert anabolic effects on the female

reproductive tractreproductive tract Uterine tubes, uterus, and vagina grow larger and Uterine tubes, uterus, and vagina grow larger and

become functionalbecome functional Uterine tubes and uterus exhibit enhanced motilityUterine tubes and uterus exhibit enhanced motility Vaginal mucosa thickens and external genitalia Vaginal mucosa thickens and external genitalia

maturemature

Estrogen-Induced Secondary Sex Estrogen-Induced Secondary Sex CharacteristicsCharacteristics

Growth of the breastsGrowth of the breasts Increased deposition of subcutaneous fat, Increased deposition of subcutaneous fat,

especially in the hips and breastsespecially in the hips and breasts Widening and lightening of the pelvisWidening and lightening of the pelvis Growth of axillary and pubic hairGrowth of axillary and pubic hair

Sexually Transmitted Diseases: Sexually Transmitted Diseases: GonorrheaGonorrhea

Bacterial infection spread by contact with Bacterial infection spread by contact with genital, anal, and pharyngeal mucosal surfacesgenital, anal, and pharyngeal mucosal surfaces

Signs and symptomsSigns and symptoms In males – painful urination, discharge of pus from In males – painful urination, discharge of pus from

the penis the penis In females – none (20%), abdominal discomfort, In females – none (20%), abdominal discomfort,

vaginal discharge, abnormal uterine bleedingvaginal discharge, abnormal uterine bleeding Left untreated, can result in pelvic inflammatory Left untreated, can result in pelvic inflammatory

diseasedisease Treatment: antibiotics, but resistant strains are Treatment: antibiotics, but resistant strains are

becoming more prevalentbecoming more prevalent

Sexually Transmitted Diseases: Sexually Transmitted Diseases: SyphilisSyphilis

Bacterial infection transmitted sexually or Bacterial infection transmitted sexually or contracted congenitallycontracted congenitally

Infected fetuses are stillborn or die shortly Infected fetuses are stillborn or die shortly after birthafter birth

A painless chancre appears at the site of A painless chancre appears at the site of infection and disappears in a few weeksinfection and disappears in a few weeks

Sexually Transmitted Diseases: Sexually Transmitted Diseases: SyphilisSyphilis

Secondary syphilis shows signs of pink skin Secondary syphilis shows signs of pink skin rash, fever, and joint painrash, fever, and joint pain

A latent period follows, which may progress to A latent period follows, which may progress to tertiary syphilis characterized by gummas tertiary syphilis characterized by gummas (lesions of the CNS, blood vessels, bones, and (lesions of the CNS, blood vessels, bones, and skin)skin)

Treatment: penicillinTreatment: penicillin

Sexually Transmitted Diseases: Sexually Transmitted Diseases: ChlamydiaChlamydia

Most common STD in the U.S.Most common STD in the U.S. Responsible for 25–50% of all diagnosed cases Responsible for 25–50% of all diagnosed cases

of pelvic inflammatory diseaseof pelvic inflammatory disease Symptoms include urethritis; penile and vaginal Symptoms include urethritis; penile and vaginal

discharges; abdominal, rectal, or testicular pain; discharges; abdominal, rectal, or testicular pain; painful intercourse; and irregular mensespainful intercourse; and irregular menses

Can cause arthritis and urinary tract infections Can cause arthritis and urinary tract infections in men, and sterility in womenin men, and sterility in women

Treatment is with tetracyclineTreatment is with tetracycline

Sexually Transmitted Diseases: Sexually Transmitted Diseases: Viral InfectionsViral Infections

Genital warts – caused by human Genital warts – caused by human papillomaviruses (HPV); infections increase papillomaviruses (HPV); infections increase the risk of penile, vaginal, anal, and cervical the risk of penile, vaginal, anal, and cervical cancerscancers

Genital herpes – caused by Epstein-Barr virus Genital herpes – caused by Epstein-Barr virus type 2 and characterized by latent periods and type 2 and characterized by latent periods and flare-upsflare-ups Congenital herpes can cause malformations of a Congenital herpes can cause malformations of a

fetusfetus Has been implicated with cervical cancerHas been implicated with cervical cancer Treatment: acyclovir and other antiviral drugsTreatment: acyclovir and other antiviral drugs

Developmental Aspects: Genetic Developmental Aspects: Genetic Sex DeterminationSex Determination

Genetic sex is determined by the sex chromosomes Genetic sex is determined by the sex chromosomes each gamete containseach gamete contains

There are two types of sex chromosomes: X and YThere are two types of sex chromosomes: X and Y Females have two X chromosomes; males have Females have two X chromosomes; males have

one X and one Yone X and one Y Hence, all eggs have an X chromosome; half the Hence, all eggs have an X chromosome; half the

sperm have an X, and the other half a Ysperm have an X, and the other half a Y A single gene on the Y chromosome, the SRY A single gene on the Y chromosome, the SRY

gene, initiates testes development and determines gene, initiates testes development and determines malenessmaleness

Developmental AspectsDevelopmental Aspects 5th week – gonadal ridges form and 5th week – gonadal ridges form and

paramesonephric (Müllerian) ducts form in females, paramesonephric (Müllerian) ducts form in females, mesonephric (Wolffian) ducts develop in malesmesonephric (Wolffian) ducts develop in males

Shortly later, primordial germ cells develop and Shortly later, primordial germ cells develop and seed the developing gonads destined to become seed the developing gonads destined to become spermatogonia or oogoniaspermatogonia or oogonia

Male structures begin development in the 7th week; Male structures begin development in the 7th week; female in the 8th weekfemale in the 8th week

External genitalia, like gonads, arise from the same External genitalia, like gonads, arise from the same structures in both sexesstructures in both sexes

Development of External Development of External Genitalia: MaleGenitalia: Male

Under the influence of testosteroneUnder the influence of testosterone Genital tubercle enlarges forming the penisGenital tubercle enlarges forming the penis Urethral groove elongates and closes Urethral groove elongates and closes

completelycompletely Urethral folds give rise to the penile urethraUrethral folds give rise to the penile urethra Labioscrotal swellings develop into the Labioscrotal swellings develop into the

scrotumscrotum

Development of External Development of External Genitalia: FemaleGenitalia: Female

In the absence of testosteroneIn the absence of testosterone Genital tubercle gives rise to the clitorisGenital tubercle gives rise to the clitoris The urethral groove remains open as the The urethral groove remains open as the

vestibulevestibule The urethral folds become labia minoraThe urethral folds become labia minora The labioscrotal swellings become labia The labioscrotal swellings become labia

majoramajora

Development Aspects: Descent of Development Aspects: Descent of the Gonadsthe Gonads

About 2 months before birth and stimulated by About 2 months before birth and stimulated by testosterone, the testes leave the pelvic cavity testosterone, the testes leave the pelvic cavity and enter the scrotumand enter the scrotum

Gubernaculum – fibrous cord that extends Gubernaculum – fibrous cord that extends from the testes to the scrotumfrom the testes to the scrotum

Spermatic cord – blood vessels, nerves, and Spermatic cord – blood vessels, nerves, and fascial layers that help suspend the testesfascial layers that help suspend the testes

Ovaries also descend, but are stopped by the Ovaries also descend, but are stopped by the broad ligament at the pelvic brimbroad ligament at the pelvic brim

Development Aspects: PubertyDevelopment Aspects: Puberty Reproductive organs grow to adult size and Reproductive organs grow to adult size and

become functionalbecome functional Secondary sex characteristics appearSecondary sex characteristics appear Characteristics of pubertyCharacteristics of puberty

Males – enlargement of the testes and scrotum, Males – enlargement of the testes and scrotum, appearance of axillary and facial hair, and growth appearance of axillary and facial hair, and growth of the penisof the penis

Females – enlarging of the breasts, menarche, and Females – enlarging of the breasts, menarche, and dependable ovulationdependable ovulation

MenopauseMenopause Ovulation and menses cease entirelyOvulation and menses cease entirely Without sufficient estrogen, reproductive Without sufficient estrogen, reproductive

organs and breasts atrophyorgans and breasts atrophy Irritability and depression resultIrritability and depression result Skin blood vessels undergo intense vasodilation Skin blood vessels undergo intense vasodilation

(hot flashes occur)(hot flashes occur) Gradual thinning of the skin and bone lossGradual thinning of the skin and bone loss

Males have no equivalent to menopauseMales have no equivalent to menopause

hormonal interactions during the ovarian cycle

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