Chapter 22 The Reproductive System (II)
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The Menstrual Cycle
o Repeated changes in the ovary and uterus during reproductive stage
o Includes the
 Ovarian cycle: cyclic changes in ___________structure and function
 Uterine cycle: cyclic changes in _________ structure and function
o Caused by changes in estrogen and progesterone concentrations
Ovarian Cycle (Figure 22.15)
o Follicular phase: Menstruation  ovulation, about ~14 days
o Luteal phase: Ovulation  before menstruation, about 14 days
o Follicular Phase
 Within an ovary, a few follicles begin to develop from primordial follicle
 Oocyte grows, granulosa cells proliferate
 Zona pellucida and antrum form
 Dominant follicle continues development, rest regress
 Corona radiata develops
 Graafian follicle = mature follicle (Figure 22.15)
 Ovulation
 Hormonal control of follicular phase: ______ and __________stimulate follicle growth and
development
o Ovulation: Day 14
 Ovulation—wall of Graafian follicle ruptures, ova released
 Released ova enters fimbrae
 Hormonal control of ovulation: ______surge triggers ovulation and development of corpus
luteum in luteal phase
o Luteal Phase
 Ruptured follicle is transformed into a gland called corpus luteum
 Corpus luteum
 Secretes _______________ and _______________
 Reaches max activity 10 days, then degenerates form corpus albican
 Degeneration: → decrease estrogens and progesterone →menstruation (end of luteal
phase)
 Is sustained by hCG if pregnancy occurs
Fraternal Twins
o Two or more follicles may become dominant and released at ovulation
o If both are fertilized—fraternal twins also called dizygotic twins (develop from two
zygotes)
Uterine Cycle and Ovarian Cycle
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Uterine Cycle (Figure 22.16)
o Menstrual Phase: Days 1-5; Shedding of uterine lining; blood flow to tissue decreases;
and issues die and slough into vagina causing menstrual flow
o Hormonal control of menstruation: triggered by decreased ___________ and _____________ when
corpus luteum degenerates
o Proliferative Phase: Days 5-14
 Uterus prepares for fertilized ovum : Endometrial lining develops: Endometrial layer grows;
endometrial glands enlarge and smooth muscle layer thickens
 Cervical glands secrete mucus
o Hormonal control of proliferative phase: _______stimulate development of uterine lining
o Secretory Phase: Days 14-28
 Endometrium prepared for implantation: Blood supply increased and glands enlarge and
secrete glycogen-rich fluids
 Cervical secretions more sticky forming a plug
o Hormonal Changes during Menstrual Cycle (Figure 22.17)
 Estrogen is first secreted from follicle, then from the corpus luteum
 Progesterone secreted from corpus luteum
 LH and FSH secreted from anterior pituitary
 Estrogens and progesterone inhibit LH and FSH secretion
o Regulation of Hormone Secretion: Mid-Follicular Phase (Figure 22.18)
o Permissive Effects of Hormones during Mid-Follicular Phase
 FSH binds to granulosa cells  theca cells
 LH binds to theca cells to stimulates them release androgens
 Estrogens promotes of expression of LH receptors on granulosa cells and Progesterone
receptors on endometrial cells
o Regulation of Hormone Secretion: Late Follicular Phase (Figure 22.19): Positive feedback
o Table 22.3 Actions of Estrogens
o Table 22.4 Actions of Progesterone
Regulation of Hormone Secretion: Luteal Phase (Figure 22.20)
Long-Term Regulation of Female Reproductive Function
o Puberty: Estrogen—secondary sex characteristics
o Reproductive years: Estrogen levels high to maintain secondary sex characteristics
o Menopause: Estrogen levels decrease
 Reversal of some secondary sex characteristics
 Hot-flashes
 Increased risk of heart disease and osteoporosis
22.4 Fertilization, Implantation, and Pregnancy
• Fertilization usually takes place in uterine tube
o Sperm must be introduced into female reproductive tract within five days before ovulation
 Sperm viable for 5 days
 Oocyte viable for 12–24 hours
o Sperm initially incapable of fertilization and it requires capacitation
• Oocyte Movement in Uterine Tube
o At ovulation, fluid movement causes oocyte to enter fimbriae of uterine tube
o Peristaltic contractions move oocyte toward uterus for several minutes
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o Activity of cilia move oocyte toward uterus for a few days
o Entire trip takes four days
o Sperm must meet ovum during these four days
Sperm Movement to Uterine Tube
o Millions of sperm deposited into vagina during copulation
o Swim to uterus and uterine tube
o Survival time in reproductive tract usually about five days
o Only few hundred sperm make it to uterine tubes
Sperm Capacitation
o Deposited sperm cannot fertilize oocyte
o Capacitation occurs in female reproductive tract
o 1st “test tube” baby
Events of Fertilization
o Several sperm generally reach ovum and try penetrating corona radiata
o When through—bind to sperm-binding protein, acrosome reaction triggers acrosome to
release enzymes. These released enzymes break through zona pellucida allowing sperm to
access oocyte.
o Fusion of sperm and oocyte stimulates 2nd meiotic division of oocyte
o Sperm plasma membrane disintegrates, chromosomes from sperm and ovum migrate to
center zygote
Early Embryonic Development and Implantation
o Mitotic divisions  morula
 Cell cleavage (no increase in overall size)
 Totipotent up to 16–32 cell stage
Identical Twins: When cells are totipotent, division of morula results in identical twins
Blastocyst
o Lost zona pellucida
o Outer cell layer = trophoblast will become fetal placenta
o Inner cell mass will become embryo
o Fluid-filled cavity = blastocoele (Figure 22.22)
Development to Blastocyst and Implantation (Figure 22.22)
o Endometrium swells, increases glycogen stores
Trophoblast Penetrates Endometrium (Figure 22.20)
o Trophoblast and endometrial cells will form placenta
Late Embryonic and Fetal Development (Figure 22.23)
o By 5 weeks, placenta is functioning, and heart is beating
Placenta Components (Figure 22.24)
o Fetal component: Chorionic villi
o Maternal component: Endometrial tissue
o Fetal and maternal blood do not mix
Placenta Functions
o Exchange nutrients, gases and waste e from fetus and mother
o Secrete hormones which maintain the pregnancy
o Human chorionic gonadotropin (hCG)
 Secrets at implantation
 Works like LH
 Is used for early pregnancy test
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 Sustains corpus luteum
Corpus luteum secretes estrogens and progesterone first two months of pregnancy
Placenta secretes estrogens and progesterone remainder of pregnancy
Hormonal Changes during Pregnancy (Figure 22.25)
 Human chorionic somatomammotropin (_______) also called placental lactogen has similar
function like GH and prolactin to mobilize energy for fetus growth and trigger diabetic-like
symptom in mother
 Estrogen is made from modified androgen released by adrenal cortex and it stimulates the
growth of duct tissue in mammary gland
 Prolactin secretion increases the growth and responsiveness of uterine muscle
 Progesterone is made from cholesterol. It stimulates the growth of glandular tissue in the
breast. It suppresses of contractile activity in uterine smooth muscle. It maintains
secretary-phase of uterine conditions
Prevention of Ovulation during Pregnancy
 Progesterone inhibits GnRH, LH, and FSH release, preventing LH surge
22.5 Parturition and Lactation
• Pregnancy = 40 weeks
• Parturition = birth
• Lactation = milk production in mammary glands
• Labor and Parturition
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Trigger for Parturition
o Unknown, but current theory suggests signal comes from fetus
 Fetal placenta: CRH → fetal ACTH → DHEA (dehydroepiandrosterone, a precursor used for
synthesis of sex hormones) estrogens: Enters maternal blood stream
o Estrogen  parturition
Lactation
o Inhibit lactation: Estrogen and progesterone
o Stimulate lactation: Prolactin and oxytocin
o Colostrum : Watery milk produced 1st few days after birth containing proteins, few nutrients
o Later milk contains nutrients, growth factors, hormones, and antibodies
Mammary Glands
o Prolactin stimulates milk synthesis
o Oxytocin stimulates the milk ejection reflex
Lactation in Response to Suckling
BPA makes canned food risky for pregnant women
Lavender and Tea Tree Oils May Cause Breast Growth in Boys
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