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Formation&Development Of Reproductive System
 

Formation&Development Of Reproductive System

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    Formation&Development Of Reproductive System Formation&Development Of Reproductive System Presentation Transcript

    • Reproduction www.freelivedoctor.com
    • Reproduction
      • Reproductive System
        • Not needed for the survival of the individual
        • Species survival
      • Sexual reproduction
        • Genes from two individual
        • Combine at random
        • Creates new combinations
        • Increases chances of species survival
      www.freelivedoctor.com
    • Sexual Reproduction
      • Each individual produces gametes
        • Formed in gonads by meiosis
          • Male: testes produce:
            • Sperm
            • Testosterone
          • Female: ovaries produce:
            • Ova
            • Estrogens, Progesterone
      • Gametes unite in process of fertilization
        • Restores diploid number
        • Forms zygote
      www.freelivedoctor.com
    • Sexual Determination
      • Each zygote inherits
        • 23 chromosomes from mother
        • 23 chromosomes from father.
        • 23 pairs of homologous chromosomes.
          • alleles
      • Kinds of chromosomes
        • 1-22 pairs of chromosomes: autosomal
        • 23 rd pair are sex chromosomes.
          • Male: XY
          • Female: XX
      • Chromosomal gender of zygote determined by fertilizing sperm.
      www.freelivedoctor.com
    • Formation of Testes
      • First 40 days after conception the gonads of males and females are similar in appearance.
      • During this time:
        • Spermatogonia and oogonia migrate from yolk sac to developing embryonic gonads
        • Gonads could become either.
      • TDF (testis-determining factor):
        • hypothetical
        • promotes the conversion to testes:
          • gene located on short arm of Y, called SRY (sex determining region of Y chromosome)
          • Found in all mammals
      www.freelivedoctor.com
    • Formation of Testes
      • Structures in the testes:
        • Seminiferous tubules: 43 to 50 days post conception
          • Germinal cells: sperm.
          • Nongerminal cells: Sertoli cells (sustentacular cells).
        • Leydig cells (interstitial cells):
          • Appear about day 65.
          • Endocrine function: secrete androgens
            • Main: Testosterone
      www.freelivedoctor.com
    • Formation of Testes
      • Leydig cells secrete testosterone.
        • Begins 8 th week and peaks at 12-14 th week.
        • Masculinizes embryonic structures.
      • Testosterone then declines to very low levels until puberty.
        • Decline occurs by end of second trimester
      • Testes descend into scrotum shortly before birth.
        • Temp about 3 degrees below internal temp
        • 35 degrees C
      www.freelivedoctor.com
    • Formation of Ovaries
      • Absence of Y chromosome and TDF, female develop ovaries.
      • Ovarian follicles do not appear until 2 nd trimester.
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • Development of Accessory Sex Organs and Genitalia
      • Presence or absence of testes determines the accessory sex organs and external genitalia.
      • Male accessory organs derived from wolffian ducts.( mesonephric )
      • Sertoli cells secrete MIF(mullerian inhibition factor).
      • Female accessory organs derived from mullerian ducts. ( paramesonephritic )
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • Development of Accessory Sex Organs and Genitalia
      • Both duct systems in both sexes between days 25 and 50
        • Regression of mullarian ducts begins about day 60
      • Testosterone
        • responsible for development of male accessory sex organs
        • External genitalia identical first 6 weeks, then testosterone stimulates development of penis
        • Not the active agent in all cells
          • converted to dihydrotestosterone (DHT) in some target cells
          • Needed for penis, spongy urethra, scrotum, prostrate
        • Testosterone directly needed for wolfian derivatives:
          • Epididymis, ductus deferens, ejaculatory duct, SV
      www.freelivedoctor.com
    • Development of Accessory Sex Organs and Genitalia www.freelivedoctor.com
    • www.freelivedoctor.com
    • Endocrine Regulation of Reproduction
      • First trimester
        • Embryonic testes are active endocrine glands
          • Secrete large amounts of testosterone
        • Embryonic ovaries not mature until third trimester
      • Time of birth:
        • Gonads in both sexes relatively inactive
      • Before puberty:
        • Low levels of sex steroids in both
        • Due to lack of stimulation
      • Puberty:
        • Increased stimulation from gonadotropic hormones
        • Induce increase in sex steroids
      www.freelivedoctor.com
    • Endocrine Regulation of Reproduction
      • Hypothalamus releases LHRH (GnRH) into hypothalamo-hypophyseal portal vessels.
      • Anterior pituitary secretes:
        • LH: luteinizing hormone.
          • In male: interstitial-cell stimulating hormone (ICSH)
        • FSH: follicle-stimulating hormone.
      • Secreted in pulsatile fashion to prevent desensitization and down regulation of receptors.
      www.freelivedoctor.com
    • Endocrine Interactions
      • Primary effects of LH and FSH on gonads:
        • Stimulation of spermatogenesis and oogenesis.
        • Stimulation of gonadal hormone secretion.
        • Maintenance of gonadal structure.
      www.freelivedoctor.com
    • Endocrine Regulation
      • Negative Feedback:
        • Inhibit GnRH from hypothalamus.
        • Inhibit anterior pituitary response to GnRH.
        • Inhibin secretion inhibit anterior pituitary release of FSH.
          • By sertoli cells
      • Female: estrogen and progesterone.
      • Male: testosterone.
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • Onset of Puberty
      • FSH and LH high in newborn, falls to low levels in few weeks.
      • Puberty: driven by increased secretion of FSH and LH
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    • Onset of Puberty
      • FSH and LH
        • Brain maturation increases GnRH secretion.
        • Decreased sensitivity of GnRH to negative feedback.
      • LH:
        • Increased secretion triggers puberty
        • Late puberty, pulsatile secretion of LH and FSH increase during sleep.
      • Stimulate a rise in sex steroid secretion.
      www.freelivedoctor.com
    • Onset of Puberty
      • Stimulate rise in testosterone and estradiol-17  .
        • Produce secondary sexual characteristics.
      • Age of onset related to the amount of body fat and physical activity in the female
      • Leptin secretion from adipocytes may be required for puberty.
      www.freelivedoctor.com
    • Pineal Gland
      • Secretes melatonin.
      • Secretion influenced by light-dark cycles.
      • Inhibit gonadotropin secretion.
      • Role in humans not established.
      www.freelivedoctor.com
    • 4 Phases of Human Sexual Response
      • Excitation phase (arousal):
        • Myotonia and vasocongestion.
        • Engorgement of a sexual organ with blood.
        • Erection of the nipples.
      • Plateau phase:
        • Clitoris becomes partially hidden.
        • Erected nipples become partially hidden by swelling of areolae.
      • Orgasm:
        • Uterus and orgasmic platform of vagina contract.
        • Contractions accompanying ejaculation.
      • Resolution phase:
        • Body return to preexcitation conditions.
      • Refractory period
        • In males
        • Erection possible, but not ejaculation
      www.freelivedoctor.com
    • Male Reproduction System
      • Testes:
        • Seminiferous tubules:
          • Where spermatogenesis occurs.
          • Contain receptor proteins for FSH in Sertoli cells.
        • Leydig cells:
          • Secrete testosterone.
          • Contain receptor proteins for LH.
      www.freelivedoctor.com
    • Control of LH and FSH Secretion
      • Negative feedback:
        • Testosterone inhibits LH and GnRH production.
        • Inhibin inhibits FSH secretion.
        • Aromatization reaction producing estadiol in the brain is required for the negative feedback effects of testosterone on LH.
        • Brain is a target organ for testosterone
          • Converted to derivatives
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • Testosterone Secretion
      • Responsible for initiation and maintenance of body changes in puberty.
      • Stimulate growth of muscles, larynx, and bone growth until sealing of the epiphyseal discs.
      • Promote hemoglobin synthesis.
      • Acts in paracrine fashion and is responsible for spermatogenesis.
      www.freelivedoctor.com
    • Testosterone Secretion
      • Negative feedback of testosterone and inhibin
        • Keep relatively constant levels of gonadotropins
        • Results in relatively constant levels
        • Different in female
          • At menopause: no more sex steroids
        • In males, gradual decrease
      www.freelivedoctor.com
    • Endocrine function: testes
      • Testosterone: main androgen
      • Sertoli and Leydig cells secrete small amounts of estradiol.
        • Have receptors for estradiol (as do other male structures)
        • May be needed for spermatogenesis
      • Estradiol may be responsible for:
        • Negative feedback in brain.
        • Sealing of epiphyseal plates.
        • Regulatory function in fertility.
      www.freelivedoctor.com
    • Spermatogenesis
      • Spermatogonia:
        • Replicate initially by mitosis.
        • Produce two cells
      • One becomes a primary spermatocytes undergoes meiosis:
        • 2 nuclear divisions.
        • 2 nd meiotic division produce 4 spermatids.
      www.freelivedoctor.com
    • Spermiogenesis
      • Maturation of spermatozoa.
      • Cytoplasm is pinched off and ingested by the Sertoli cell cytoplasm.
      www.freelivedoctor.com
    • Sertoli Cells
      • Blood-testes barrier:
        • Prevents autoimmune destruction of sperm.
        • Produce FAS ligand which binds to the FAS receptor on surface to T lymphocytes, triggering apoptosis.
      • Secretes inhibin.
      • Phagocytize residual bodies:
        • Transmit information molecules from germ cells to Sertoli cells.
      • Secrete ABP (androgen-binding protein):
        • Binds to testosterone and concentrates testosterone in the tubules.
      www.freelivedoctor.com
    • Hormonal Control of Spermatogenesis
      • Testosterone required for completion of meiosis and spermatid maturation.
      • Testes secrete paracrine regulators:
        • IGF-1.
        • Inhibin.
      • FSH necessary in the later stages of spermatid maturation.
      www.freelivedoctor.com
    • Male Accessory Organs
      • Epididymis:
        • Maturational changes.
        • Resistance to pH changes and temperature.
        • Storage.
      • Prostate secretes:
        • Alkaline fluid.
        • Citric acid.
        • Ca ++ .
        • Coagulation proteins.
      • Seminal vesicles secrete:
        • Fructose.
      www.freelivedoctor.com
    • Erection, Emission, and Ejaculation
      • Erection:
        • Increased vasodilation of arterioles.
        • NO is the NT.
        • Blood flow into the erectile tissues of the penis.
        • Parasympathetic
      • Emission:
        • Movement of semen into the urethra.
        • Sympathetic
      • Ejaculation:
        • Forcible expulsion of semen from the urethra out of the penis.
        • Sympathetic
      www.freelivedoctor.com
    • Female Reproductive System
      • Ovaries:
        • Contain large number of follicles which enclose ova.
        • Extensions called fimbriae partially cover each ovary.
        • At ovulation, secondary oocyte is extruded.
      www.freelivedoctor.com
    • Female Reproductive System
      • Fallopian (uterine) tubes:
        • Ova drawn into the tube by cilia.
      • Uterus:
        • Womb.
        • Endometrium shed during menstruation.
      • Vagina:
        • Cervical mucus plug.
      www.freelivedoctor.com
    • Ovarian Cycle
      • 5 mo. gestation ovaries contain 6-7 million oogonia.
      • Oogenesis arrested in prophase of 1 st meiotic division (primary oocyte).
      • Apoptosis occurs:
        • 2 million primary oocytes at birth.
        • 400,000 primary oocytes at puberty.
      • 400 oocytes ovulated during the reproductive years.
      www.freelivedoctor.com
    • Ovarian Cycle
      • Primary oocytes contained in primary follicles.
        • FSH stimulates cell growth.
      • Develop into secondary follicles.
      • Fusion of its vesicles into the antrum.
      • Mature graafian follicle:
      • 1 st meiotic division completed (secondary oocyte).
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • Ovarian Cycle
      • Secondary oocyte:
      • Under FSH stimulation:
        • Theca cells secrete testosterone. Granulosa cells: contain the enzyme aromatase to convert testosterone into estrogen.
      www.freelivedoctor.com
    • Ovulation
      • Graafian follicle forms bulge on surface of ovary.
      • Extrudes secondary oocyte into the uterine tube.
      • Empty follicle becomes corpus luteum and secretes:
        • Progesterone.
        • Estrogen.
        • If not fertilized becomes corpus albicans.
      www.freelivedoctor.com
    • Menstrual Cycle
      • 3 phases: Ovarian
        • Follicular Phase
        • Ovulation
        • Luteal Phase
      • Duration approximately 28 days.
      • Day 1 is the first day of menstruation.
      www.freelivedoctor.com
    • Follicular Phase
      • FSH:
      • Stimulates production of FSH receptors on granulosa cells.
        • Follicles grow and become secondary follicle.
      • Granulosa cells secrete estradiol.
      • Increases sensitivity of FSH receptors.
      • FSH and estradiol stimulate production of LH receptors in graafian follicle.
      www.freelivedoctor.com
    • Follicular Phase
      • Rapid rise in estradiol:
        • Negative feedback on LH and FSH.
      • Hypothalamus increase frequency of GnRH pulses.
      • Augments the ability of anterior pituitary to respond to GnRH to increase LH secretion.
      www.freelivedoctor.com
    • Follicular Phase
      • Positive feedback:
        • LH surge begins 24 hours before ovulation.
        • Triggers ovulation.
      • FSH increase stimulates development of new follicles.
      www.freelivedoctor.com
    • Ovulation
      • Under FSH, graafian follicle grows large and thin-walled.
        • Triggers LH surge.
      • Wall of graafian follicle ruptures.
      • Day 14.
      • Ist meiotic division is completed.
      www.freelivedoctor.com
    • Luteal Phase
      • LH stimulates formation of the empty follicle into corpus luteum.
      • Corpus luteum secretes:
        • Progesterone:
        • Plasma concentration rapidly rises.
        • Estradiol.
      • Negative feedback on LH and FSH.
      • Inhibin: suppress FSH.
      www.freelivedoctor.com
    • Luteal Phase
      • Corpus luteum regresses unless fertilization occurs:
        • Estradiol decreases.
        • Progesterone decreases.
      • Withdrawal of estradiol and progesterone cause menstruation to occur.
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • www.freelivedoctor.com
    • Endometrial Changes
      • 3 phases of endometrium changes:
        • Proliferative phase.
        • Secretory phase.
        • Menstrual phase.
      www.freelivedoctor.com
    • Proliferative Phase
      • Ovary is in follicular phase.
      • Estradiol stimulate growth of endometrium.
      • Spiral arteries develop.
      • Stimulate production of receptor proteins for progesterone.
      • Cornification of vaginal epithelium occurs.
      www.freelivedoctor.com
    • Secretory Phase
      • Ovary is in luteal phase.
      • Progesterone stimulates development of uterine glands, which become engorged with glycogen.
      • Endometrium becomes thick, vascular and spongy.
      • Cervical mucus thickens and becomes sticky.
      www.freelivedoctor.com
    • Menstrual Phase
      • Progesterone cause constriction of spiral arteries.
      • Necrosis and sloughing of endometrium occurs.
      • Lasts 1-5 days.
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • Menopause
      • Cessation of ovarian activity.
      • Age ~ 50 years.
      • Ovaries depleted of follicles.
      • Estradiol and inhibin withdrawl causes hot flashes, and atrophy of the vaginal wall.
      • LH and FSH increase.
      www.freelivedoctor.com
    • Fertilization
      • Ejaculation 300 million sperm, 100 reach (uterine) fallopian tube.
      • Fertilization occurs in the uterine tubes
      • Acrosomal reaction:
        • Acrosome of sperm contains hyaluronidase, an enzyme that digests a channel through zona pellucida.
      • Sperm fuses with ovum cell membrane.
      www.freelivedoctor.com
    • Fertilization
      • As fertilization occurs, secondary oocyte completes 2 nd meiotic division.
      • Sperm enters ovum cytoplasm.
      • Ovum nuclear membrane disappears, zygote formed.
      www.freelivedoctor.com
    • Blastocyct Formation
      • Cleavage:
        • 30-36 hrs. after fertilization the zygote divides by mitosis.
      • Blastocyst develops:
        • Inner cell mass: fetus.
        • Surrounding chorion: trophoblasts form placenta.
      www.freelivedoctor.com
    • Implantation
      • 6 th day after fertilization, blastocyst attaches to uterine wall.
      • Blastocyst secretes enzymes that allow blastocyst to burrow into endometrium.
      • Trophoblast cells secrete hCG.
      www.freelivedoctor.com
    • hCG
      • Human chorionic gonadotropin.
      • Trophoblast cells secrete hCG.
      • Signals corpus luteum not to degenerate until placenta secretes adequate [hormone].
      • Effects similar to LH.
      • Basis of pregnancy test.
      www.freelivedoctor.com
    • Placenta
      • Syncytiotrophoblast secretes enzymes that create blood filled cavities in the maternal tissue.
      • Cytotrophoblast then from projections (villi) that grow into the venous blood.
        • Producing chorion frondosum on the side that faces the uterine wall.
      • Other side of chorion bulges into the uterine cavity.
      www.freelivedoctor.com
    • Placental Changes
      • Decidual reaction:
        • Endometrial growth.
        • Accumulation of glycogen.
      • Decidua basalis: maternal tissue in contact with the chorion frondosum.
      • Maternal and fetal blood do not mix.
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    • Amnion
      • Envelop the embryo.
      • Amnionic fluid contains sloughed cells of the fetus.
      www.freelivedoctor.com
    • Placenta Function
      • Gas exchange:
        • 0 2 and C0 2 .
      • Nutrient exchange.
      • Waste exchange.
      • Synthesis of proteins and enzymes.
      www.freelivedoctor.com
    • Placental Hormones
      • hCS:
      • Chorionic somatomammotropin.
      • GH effects.
      • Diabetic-like effect:
        • Glucose sparing effect.
        • Polyuria.
        • Lipolysis.
      www.freelivedoctor.com
    • Placental Hormones
      • Fetal-placental unit:
        • Placenta must cooperate with the adrenal cortex in the fetus to produce estrogen.
      • Estrogen stimulates:
        • Endometrial growth.
        • Inhibit prolactin secretion.
        • Growth of mammary ducts.
        • Enlargement of mother’s uterus.
      www.freelivedoctor.com
    • Placental Hormones
      • Progesterone:
        • Suppresses uterine contractions.
        • Stimulates uterine growth .
        • Suppresses LH and FSH.
        • Stimulate development of alveolar tissue of the mammary gland.
      www.freelivedoctor.com
    • Parturition
      • Estrogen in late pregnancy:
        • Increases amount of oxytocin stored.
        • Stimulate production of oxytocin receptors in myometrium.
        • Stimulate prostaglandin production.
      • Uterine contractions:
        • Oxytocin.
        • Prostaglandins.
      www.freelivedoctor.com
    • Lactation
      • Hypothalamus releases PRH.
      • Anterior pituitary releases prolactin:
        • Stimulate milk production.
      • Oxytocin needed for “milk letdown”.
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    • www.freelivedoctor.com
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