Formation&Development Of Reproductive System
Upcoming SlideShare
Loading in...5
×
 

Formation&Development Of Reproductive System

on

  • 3,730 views

 

Statistics

Views

Total Views
3,730
Views on SlideShare
3,730
Embed Views
0

Actions

Likes
0
Downloads
191
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

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
    www.freelivedoctor.com
  • 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.
    www.freelivedoctor.com
  • 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”.
    www.freelivedoctor.com
  • www.freelivedoctor.com
  • www.freelivedoctor.com