hormones affecting reproduction
TRANSCRIPT
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Part 5: Reproduction
Endocrine System
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Reproductive System
Male FemaleGonad Testes OvaryGamete Sperm Ovum (egg)Hormones Androgens:
testosterone, androsterone
Estrogenprogesterone
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Male Anatomy
Fig. 46.8
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Cells of the Testes
Leydig interstitial cells synthesize hormones (androgens)
Sertoli cells synthesize sperm (spermatogenesis)
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Male Reproductive Hormones: Androgens
androsterone
testosterone
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Male Reproductive Hormones: Androgensboth hormones are released from
testes
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Androgen: Testosterone
Steroid hormone Develops male primary and
secondary sexual characteristics
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Primary Sexual CharacteristicsAssociated with the reproductive
systemDevelopment of vas deferens,
external reproductive structuresStimulate spermatogenesis: sperm
production in sertoli cells (lifetime process)
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Secondary Sexual CharacteristicsNot directly related to the
reproductive systemDevelops characteristics at puberty
deepening of voice facial and pubic hair muscle growth increased secretion of body oils
(associated with body odour)
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Male Reproductive Hormones
1. Hypothalamus: Gonatropin releasing hormone (GnRH)
2. Anterior Pituitary: Gonadotropic hormones FSH & LH
3. Sertoli cells: FSH stimulates spermatogenesis
4. Leydig cells: LH stimulates hormone (androgen) secretion
5. Androgen testosterone affects primary & secondary sexual characteristics
Hypothalamus
Anterior pituitary
testes
Sertoli cells
Leydig cells
GnRH
FSH LH
testosterone
sperm production
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Gonadotropic Hormones
Two types: Follicle stimulating hormone (FSH) Luteinizing hormone (LH)
Peptide hormonesPresent in both male and female
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Gonadotropins in Males
FSH: act on Sertoli cells to increase spermatogenesis (nontropic)
LH: stimulate Leydig cells to make androgens (tropic)
Image Source: http://www.andrologyaustralia.org/images/pageContentImages/MI_Image_Jul2005_04HormonalLinks.jpg
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Male Reproductive Hormone:Neuroendocrine pathway - nontropic
Location HormoneHypothalamus Gonadotropin-Releasing
Hormone (GnRH)Anterior Pituitary
Gonadotropins:Follicle-stimulating hormone (FSH)
Effect: Sertoli cells
Spermatogenesis
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Male Reproductive Hormone:Neuroendocrine pathway - tropic
Location HormoneHypothalamus Gonadotropin-Releasing
Hormone (GnRH)Anterior Pituitary
Gonadotropins:Lutenizing hormone (LH)
Testes: Leydig cells
Androgens: testosterone
Effect Primary and secondary sexual characteristics
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Fig. 46.14
Male Reproductive Hormonal Control
hypothalamus
pituitary
testes
Sertoli cells
Leydig cells
GnRH
FSH LH
testosterone
sperm production
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Negative Feedback
Testosterone negatively feedback to the hypothalamus and pituitary to decrease the production of GnRH and LH
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Female Reproductive Systemcomparatively more complicated
than male reproductive systemmonthly cycle until menopause (~12
to 50 yrs)one ovum produced per germ cell
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Female Anatomy
Fig. 46.9
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Female Reproductive Hormones
estrogen
progesterone
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Female Reproductive Hormonesboth produced in the ovaries
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Image Sources: Wikipedia, http://en.wikipedia.org/wiki/Estrogen, http://trollydolly.us/wp-content/uploads/2009/04/estrogen-cartoon.gif
Estrogens
Female sex hormonesThree compounds
Estradiol is predominant
Develops secondary sexual characteristics Breast development Wider hips Fat deposition
Estradiol
Estrone
Estriol
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Ovary Follicle Cells
primary oocyte: egg that can be fertilized by sperm
granulosa cells: provide nutrients for primary oocyte
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Ovarian Cycle Regulation:Neuroendocrine pathwayLocation HormoneHypothalamus Gonadotropin-Releasing
Hormone (GnRH)Anterior Pituitary
Gonadotropins:Follicle-stimulating hormone (FSH)Lutenizing hormone (LH)
Ovaries: Follicle & Corpus Luteum
EstrogenProgesterone
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Gonadotropin-Releasing Hormone (GnRH)
GnRH levels not shown in graph or right but correlates to the rise in LH/FSH levels
Released in slow waves during follicular phase
Rate of release is increased (peaked) when approaching ovulation
Rate decreases greatly during luteal phase
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Gonadotropins in FemalesFSH:
Stimulates growth of follicle (maturation) in follicular phase
LH: lutenizes the follicle
into the corpus luteum
Induces ovulation Matures the corpus
luteum in luteal phase
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Ovarian Cycle Follicular phase
Growth of several follicles but only one matures while others disintegrate
Egg in follicle enlarges Coat of follicle thickens Fluid-filled cavity inside follicle develops and bulges
Ovulation Follicle and wall of ovary rupture Egg is released
Luteal phase Follicular tissue develops into corpus luteum Corpus luteum secretes female hormones
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Fig. 46.13b
Ovulation
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Ovulation
EGG CELL
Fig. 46. 10
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hypothalamus
pituitary
ovaries
follicle corpus luteum
GnRH
FSH LH
progesteronesome estrogen
estrogen
1 2
ovulation
Female Reproductive Hormone Control
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ProgesteroneCorpus luteum
secretes progesterone (and some estrogens)
Correlates to thickening of endometrium in order to accept
fertilized egg and enable implantation and growth
Image Source: Wikipedia, http://en.wikipedia.org/wiki/Progesterone
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Progesterone If no implantation then
corpus luteum disintegrates progesterone isn’t
secreted Decreased progesterone
levels leads to: stop of endometrium
growth endometrium breaks
down (menstruation)
Image Source: Wikipedia, http://en.wikipedia.org/wiki/Progesterone
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Menstrual Cycle
Day 1 = first day of menstruation Menstrual flow phase
sloughing of endometrial lining menstrual bleeding
Proliferative phase endometrium regenerates and thickens
Secretory phase endometrium continues to thicken becomes more vascularized (blood vessels) develops glands to secrete fluid rich in glycogen
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hypothalamus
pituitary
ovaries
follicle corpus luteum
GnRH
FSH LH
progesteronesome estrogen
estrogen
1 2
ovulation
Female Reproductive Hormone Control
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Follicle
Granulosa cells of follicle secretes estrogen
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Estrogen Regulation: High levels
High estrogen: Positive feedback on LH & FSH by stimulating GnRH
Estrogen surge from follicle during day 12-14 LH & FSH surge Results in ovulation
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Estrogen Regulation
Also responsible for the early thickening of the endometrium in the proliferative phase
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Estrogen Regulation: Low levels
Estrogen secreted at low levels during most of the cycle
Negative feedback on GnRH, LH & FSH
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Estrogen Regulation
Corpus luteum secretes estrogen and progesterone
Both act together to negatively feedback on GnRH, LH & FSH
Prevents ovulation
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Dual Role of Estrogen
Low estrogen concentration negative feedback
High estrogen concentration positive feedback
http://www.sumanasinc.com/webcontent/animations/content/ovarianuterine.html
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Female Reproductive Hormone Control
hypothalamus
pituitary
ovaries
follicle corpus luteum
GnRH
FSH LH
progesteronesome estrogen
estrogen
1 2
ovulation
Day 12-14 when estrogen levels surge
Day 12-14 when estrogen levels surge
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Fig. 46.15
Overview of Female Reproductive Cycles
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Fig. 46.15
Hormonal Control in Follicular phase Immature follicles
have receptors for FSH but not LH
FSH stimulate follicular growth
Granulosa cells of the growing follicles secrete estrogen
Low levels of estrogen negatively feeds back on LH and FSH
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Fig. 46.15
Hormonal Control near ovulation Estrogen surge
Positive feedback on LH & FSH by stimulating GnRH
Mature follicle have receptors for LH
LH induces ovulation Estrogen also
stimulates thickening of endometrium
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Fig. 46.15
Hormonal Control in Luteal Phase LH lutenizes
remaining follicular tissue into corpus luteum
Corpus luteum secretes estrogen and progesterone
Both act together to negatively feedback on GnRH, LH & FSH
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Fig. 46.15
Hormonal Control in Luteal Phase Corpus luteum
disintegrates Sharp decline in
estrogen & progesterone
Negative feedback removed Secretion of GnRH, LH &
FSH begins Disintegration of
endometrium
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Menopause
Occur around age 46-54Ovaries lose responsiveness to
gonadotropins Decline in estrogen production Cessation of ovulation and menstruation