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Hormones affecting reproduction
 

Hormones affecting reproduction

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    Hormones affecting reproduction Hormones affecting reproduction Presentation Transcript

    • Endocrine SystemPart 5: Reproduction
    • Reproductive System Male FemaleGonad Testes OvaryGamete Sperm Ovum (egg)Hormones Androgens: Estrogen testosterone, progesterone androsterone
    • Male Anatomy Fig. 46.8
    • Cells of the Testes Leydig interstitial cells synthesize hormones (androgens) Sertoli cells synthesize sperm (spermatogenesis)
    • Male Reproductive Hormones:Androgens androsterone testosterone
    • Male Reproductive Hormones:Androgens both hormones are released from testes
    • Androgen: Testosterone Steroid hormone Develops male primary and secondary sexual characteristics
    • Primary Sexual Characteristics Associated with the reproductive system Development of vas deferens, external reproductive structures Stimulate spermatogenesis: sperm production in sertoli cells (lifetime process)
    • Secondary Sexual Characteristics Not directly related to the reproductive system Develops characteristics at puberty  deepening of voice  facial and pubic hair  muscle growth  increased secretion of body oils (associated with body odour)
    • Male Reproductive Hormones Hypothalamus 1. Hypothalamus: Gonatropin GnRH releasing hormone (GnRH) Anterior pituitary 2. Anterior Pituitary: Gonadotropic hormones FSH & LHFSH LH 3. Sertoli cells: FSH stimulates spermatogenesis testes 4. Leydig cells: LH stimulates Sertoli Leydig hormone (androgen) secretion cells cells 5. Androgen testosterone affects primary & secondary sexual testosterone characteristics sperm production
    • Gonadotropic Hormones Two types:  Follicle stimulating hormone (FSH)  Luteinizing hormone (LH) Peptide hormones Present in both male and female
    • 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
    • Male Reproductive Hormone:Neuroendocrine pathway - nontropic Location Hormone Hypothalamus Gonadotropin-Releasing Hormone (GnRH) Anterior Pituitary Gonadotropins: Follicle-stimulating hormone (FSH) Effect: Sertoli Spermatogenesis cells
    • Male Reproductive Hormone:Neuroendocrine pathway - tropic Location Hormone Hypothalamus Gonadotropin-Releasing Hormone (GnRH) Anterior Pituitary Gonadotropins: Lutenizing hormone (LH) Testes: Leydig Androgens: testosterone cells Effect Primary and secondary sexual characteristics
    • Male Reproductive Hormonal Control hypothalamus GnRH pituitaryFSH LH testes Sertoli Leydig cells cells testosterone sperm production Fig. 46.14
    • Negative Feedback Testosterone negatively feedback to the hypothalamus and pituitary to decrease the production of GnRH and LH
    • Female Reproductive System comparatively more complicated than male reproductive system monthly cycle until menopause (~12 to 50 yrs) one ovum produced per germ cell
    • Female Anatomy Fig. 46.9
    • Female Reproductive Hormones estrogen progesterone
    • Female Reproductive Hormones both produced in the ovaries
    • Estrogens Female sex hormones Estriol Three compounds  Estradiol is predominant Develops secondary sexual characteristics Estradiol  Breast development  Wider hips  Fat deposition Estrone Image Sources: Wikipedia, http://en.wikipedia.org/wiki/Estrogen, http://trollydolly.us/wp-content/uploads/2009/04/estrogen-cartoon.gif
    • Ovary Follicle Cells primary oocyte: egg that can be fertilized by sperm granulosa cells: provide nutrients for primary oocyte
    • Ovarian Cycle Regulation:Neuroendocrine pathwayLocation HormoneHypothalamus Gonadotropin-Releasing Hormone (GnRH)Anterior Pituitary Gonadotropins: Follicle-stimulating hormone (FSH) Lutenizing hormone (LH)Ovaries: Follicle & EstrogenCorpus Luteum Progesterone
    • Gonadotropin-ReleasingHormone (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
    • Gonadotropins in Females FSH:  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
    • 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
    • Ovulation Fig. 46.13b
    • Ovulation EGG CELLFig. 46. 10
    • Female Reproductive HormoneControl hypothalamus GnRH pituitary 1 2 FSH LH ovaries corpus follicle luteum estrogen progesterone some estrogen ovulation
    • Progesterone Corpus 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
    • 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
    • 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
    • Female Reproductive HormoneControl hypothalamus GnRH pituitary 1 2 FSH LH ovaries corpus follicle luteum estrogen progesterone some estrogen ovulation
    • Follicle Granulosa cells of follicle secretes estrogen
    • 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
    • Estrogen Regulation Also responsible for the early thickening of the endometrium in the proliferative phase
    • Estrogen Regulation: Low levels Estrogen secreted at low levels during most of the cycle Negative feedback on GnRH, LH & FSH
    • Estrogen Regulation Corpus luteum secretes estrogen and progesterone Both act together to negatively feedback on GnRH, LH & FSH Prevents ovulation
    • Dual Role of Estrogen Low estrogen concentration  negative feedback High estrogen concentration  positive feedback http://www.sumanasinc.com/webcontent/animations/content/ovarianuterine.html
    • Female Reproductive HormoneControl Day 12-14 when hypothalamus estrogen levels surge GnRH Day 12-14 when pituitary estrogen levels surge 1 2 FSH LH ovaries corpus follicle luteum estrogen progesterone some estrogen ovulation
    • Overview ofFemaleReproductiveCycles Fig. 46.15
    • Hormonal Controlin 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 Fig. 46.15
    • Hormonal Controlnear 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 Fig. 46.15
    • Hormonal Controlin 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 Fig. 46.15
    • Hormonal Controlin Luteal Phase Corpus luteum disintegrates Sharp decline in estrogen & progesterone Negative feedback removed  Secretion of GnRH, LH & FSH begins Disintegration of endometrium Fig. 46.15
    • Menopause Occur around age 46-54 Ovaries lose responsiveness to gonadotropins  Decline in estrogen production  Cessation of ovulation and menstruation