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Reproductive Physiology

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Reproductive Physiology Part 1 The Basics of Reproductive Physiology Part 2 Female Reproductive Physiology Part 3 Male Reproductive Physiology – PowerPoint PPT presentation

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Title: Reproductive Physiology


1
Reproductive Physiology
  • Part 1 The Basics of Reproductive Physiology
  • Part 2 Female Reproductive Physiology
  • Part 3 Male Reproductive Physiology

2
Lecture Outline
  • The Basics
  • Gametogenesis
  • Gender determination
  • The Pituitary-Gonad Axis
  • Female Reproductive Physiology
  • Ovarian Cycle
  • Uterine Cycle
  • Hormonal control and changes
  • Male Reproductive Physiology

3
The BasicsGametogenesis
  • Gametes are produced during Meiosis I II
  • Meiosis function
  • Production of 4 haploid (n) gametes from each
    diploid oögonium (2n) or spermatogonium (2n)
  • Differences between ? (male) and ? (female)
    gamete development
  • ?
  • continuous development production of sperm from
    onset of puberty until.?
  • stem cells are retained
  • Sperm are motile and contain very little
    cytoplasm
  • ?
  • the entire complement of dictyate primary oocytes
    are formed during development with 10-20
    continuing development during each ovarian cycle
  • Oocytes are surrounded by follicular cells
    forms ovarian follicle
  • stem cells are exhausted
  • oocytes are among the largest cells and are
    non-motile

4
The BasicsGametogenesis
  • Sperm Production
  • During development germ cells are produced
  • Remain quiescent until puberty
  • Actions of hormones from pituitary, sertoli cells
    and Leydig cells
  • At puberty some spermatogonia will
  • Undergo mitosis continuously
  • Enter into meiosis
  • This ensures a continuous supply of spermatogonia

5
The BasicsGametogenesis
  • Process of sperm production involves three stages
  • Spermatocytogenesis
  • produces secondary spermatocytes from
    spermatogoium
  • Spermatidogenesis
  • stage where meiosis I II occur
  • results in spermatid formation
  • Spermiogenesis
  • final stage of sperm development
  • spermatid becomes a motile spermatozoa during
    spermiation

6
The BasicsGametogenesis
  • Spermiation
  • The spermatozoa that are formed are initially
    unable to move.
  • The flagella must become motile
  • Not used however until ejaculated
  • Prior movement through the male reproductive
    tract is via peristalsis

End result!
7
The BasicsGametogenesis
  • Oogenesis
  • Results in formation of secondary oocyte which is
    released during ovulation
  • If no fertilization occurs, meiosis II will not
    occur.
  • Stages of oogenesis
  • Oocytogenesis
  • Forms oögonia
  • During fetal development starting at week 10 and
    completing around birth
  • Results in formation of primary oocytes (1/2
    million)
  • Ootidogenesis
  • Results in the formation of secondary oocytes
  • These are dictyate in prophase I
  • Formation of ovum (if fertilization occurs)

8
The BasicsGametogenesis
9
The BasicsGender Determination
  • Chromosomes determine gender
  • 23 donated by egg (n)
  • 23 donated by sperm (n)
  • Syngamy
  • The fusion of gametes to form a zygote
  • Consists of
  • plasmogamy
  • union of cell membranes and cytosol
  • Karyogamy
  • union of genetic material
  • Autosomes 44 or 22 pair
  • Sex chromosomes 2 or 1 pair
  • XX chromosomes female
  • XY chromosomes male

What happens if karyogamy of sex chromosomes is
different?
10
The BasicsGender Determination
  • Non-disjunction during meiosis I or II
  • Monosomy or polyploidy
  • XO (no Y chromosome, or second X)
  • Turners syndrome
  • Phonotypical female

What about YO monosomy?
11
The BasicsGender Determination
  • Non-disjunction during meiosis I or II
  • Polyploidy
  • The incomplete separation of homologues during
    meiosis results in a zygote with too many
    chromosomes
  • Regarding the sex chromosomes, it may be
  • XXY (47 chromosomes total)
  • Klinefelter syndrome Male sex organs unusually
    small testes, sterile. Breast enlargement and
    other feminine body characteristics. Normal
    intelligence.
  • XYY
  • Jacobs syndrome Individuals are somewhat taller
    than average and often have below normal
    intelligence. At one time (1970s), it was
    thought that these men were likely to be
    criminally aggressive, but this hypothesis has
    been disproven over time.
  • XXYY male and very rare (48 chromosomes)
  • XXX (Trisomy X)
  • Individuals are female normal, undistinguishable
    except for by karyotype.

12
The BasicsGender Determination
  • The embryo exhibits gender bipotential
  • Around week seven of fetal development the SRY
    (Sex-determining Region of Y chromosome) gene
    becomes activated
  • The SRY directs the bipotential gonads
  • The absence of this on the X chromosome causes
    the gonads to develop into ovaries
  • Ovaries then produce further gender biased
    hormones
  • The presence of this gene and its products causes
    the gonads to descend and develop into testes
  • Testes then produce further gender biased
    hormones
  • Translocation of the gene to X chromosome results
    in an XX individual (genotype) but with XY
    characteristics (phenotype)

13
The BasicsGender Determination
  • Effects of SRY on sex organ development

14
The BasicsGender Determination
  • Indirect effects of SRY on male and female
    genital development

15
Lecture Outline
  • The Basics
  • Gametogenesis
  • Gender determination
  • The Pituitary-Gonad Axis
  • Female Reproductive Physiology
  • Ovarian Cycle
  • Uterine Cycle
  • Hormonal control and changes
  • Male Reproductive Physiology

16
The Pituitary-Gonad Axis
17
Lecture Outline
  • The Basics
  • Gametogenesis
  • Gender determination
  • The Pituitary-Gonad Axis
  • Female Reproductive Physiology
  • Ovarian Cycle
  • Uterine Cycle
  • Hormonal controls changes
  • Male Reproductive Physiology

18
Female Reproductive PhysiologyBasics
  • The hypothalamus-pituitary-gonad axis controls
    the required physiologic changes that occur both
    in the ovaries and in the uterus of the menstrual
    cycle.
  • The Menstrual Cycle
  • Duration
  • Approximately 28 days (ranges 24 35 days)
  • Starts with the removal of the endometrium
    release of FSH by the anterior pituitary
  • The ovarian cycle
  • Development of ovarian follicle
  • Production of hormones
  • Release of ovum during ovulation
  • The uterine cycle
  • Removal of endometrium from prior uterine cycle
  • Preparation for implantation of embryo under the
    influence of ovarian hormones

19
Female Reproductive PhysiologyThe Cycles
  • Three Phases of the Ovarian Cycle
  • Follicular phase
  • Ovulation phase
  • Luteal phase
  • Three Phases of the Uterine Cycle
  • Menses
  • Proliferative Phase
  • Secretory Phase
  • These ovarian and uterine phases are intimately
    linked together by the production and release of
    hormones

20
Female Reproductive PhysiologyThe Cycles
  • Hormonal control of the ovarian cycle

21
Female Reproductive PhysiologyThe Cycles
  • Hormonal control of the uterine cycle

22
Female Reproductive PhysiologyAll together
23
Female Reproductive PhysiologyFertilization
Effects
  • What happens if fertilization occurs?
  • Uterine endometrium is maintained by
  • First the release of progesterone from the corpus
    lutem,
  • then the release of hCG (human chorionic
    gonadotropin) which maintains the corpus luteum
    until the 7th week,
  • From 7th week on, the placenta produces
    progesterone which continues to maintain the
    endometrium the corpus luteum degenerates
  • Placenta also produces estrogen and progesterone
    which at high levels blocks GnRH
  • Estrogen is also involved in breast development
  • Progesterone is also involved in uterine
    maintenance and relaxation (prevents premature
    contractions)
  • Placenta also produces hPL (human placental
    lactogen)
  • Implicated in breast development and milk
    production
  • Though determined not the only factor as lack of
    hPL has no ill effects
  • More important is the role hPL plays in fetal
    nutrition by altering maternal glucose and fatty
    acid metabolism

24
Female Reproductive PhysiologyFertilization
Effects
  • What changes occur to allow parturition?
  • Increasing levels of corticotropin-releasing
    hormone (CRH) from the placenta a few weeks prior
    to delivery
  • Early deliveries have been linked to early
    elevated levels of CRH
  • During delivery
  • progesterone levels drop off
  • Oxytocin levels rise
  • Oxytocin receptors on the uterus are upregulated
    during gestation
  • Inhibin levels increase
  • Relax the cervix and ligaments of the pelvis
  • Allows for increased stretch of the cervix which
    triggers additional oxytocin which triggers
    stronger uterine contractions which increase
    stretch of the cervix which triggers oxytocin
    which triggers stronger uterine contractions
    which increases stretch of the cervix which
    increases oxytocin release which increases
    uterine contractions which increases stretch on
    cervix which.

25
Female Reproductive PhysiologyOne Possible
Outcome
26
Female Reproductive PhysiologyOr.
27
Lecture Outline
  • The Basics
  • Gametogenesis
  • Gender determination
  • The Pituitary-Gonad Axis
  • Female Reproductive Physiology
  • Ovarian Cycle
  • Uterine Cycle
  • Hormonal control and changes
  • Male Reproductive Physiology

28
Male Reproductive PhysiologyBasic Functions
  • Function
  • Produce, maintain transport viable spermatozoa
  • Testes
  • Epididymis
  • Ductus deferens
  • Accessory glands
  • Prostate
  • Seminal vesicles
  • Bulbourethral glands
  • Hormone production that
  • develops secondary sexual characteristics
  • Involved in feedback mechanisms relating to
    spermatogenesis

29
Male Reproductive PhysiologyTestes
  • Site of Sperm production
  • Divided into lobules, each with seminiferous
    tubules.
  • Seminiferous tubule functions to
  • Maintain environment for spermatogonia by the
    basal lamina and the Sertoli cells
  • Sertoli cells separate the lumen from the basal
    lamina and create a blood-testis barrier
  • Creates three compartments
  • Lumen low glucose, high K steroid hormones
  • Basal compartment the baso-lateral side of the
    sertoli cells containing the developing
    spermatogonia
  • Interstitial fluid space below the basal
    lamina and contains the Leydig cells
  • Produce hormones/paracrines
  • From Sertoli cells
  • From Leydig cells

30
Male Reproductive PhysiologyTestis
  • Sertoli cells
  • Produce hormones paracrines involved with
    control of hypothalamus-pituitary-gonad axis and
    the testes directly
  • Anti-Müllerian Hormone (AMH)
  • Secreted during embryogenesis
  • Prevents development of the Müllerian ducts
  • Inhibin activin
  • Regulate FSH release from anterior pituitary
  • inhibin decreases FSH release
  • activin increases LH function increases FSH
    release
  • Androgen Binding Protein (ABP)
  • Binds to testosterone and DHT, reduces the loses
    due to diffusion resulting in an increase in
    testicular testosterone levels
  • Estradiols Aromatase
  • Support spermatogenesis

31
Male Reproductive PhysiologyTestis
  • Sertoli cells, cont
  • GDNF (glial derived neurotrophic factor) ERM
    transcription factor
  • Maintenance of the stem cell line
  • Leydig cells
  • Produce androgens
  • testosterone, androstenedione and
    dehydroepiandrosterone (DHEA)
  • Increase spermatogenesis
  • Influence secondary sexual characteristics
  • Stimulated to produce androgens by luteinizing
    hormone (LH)
  • FSH increases the response to LH by Leydig cells

32
Male Reproductive PhsyiologyTestes
33
Male Reproductive PhysiologyTestes
  • Spermatogenesis Hormonal Control Flow Chart

34
Male Reproductive PhysiologyAccessory Gland
Function
  • Job of the accessory glands is to
  • Secrete seminal fluid (99 of semen volume)
  • Components of seminal fluid
  • Mucus
  • Water
  • Nutrients
  • Buffers
  • Enzymes
  • Prostaglandins
  • Zinc?
  • Accessory Glands
  • Prostate
  • Seminal vesicles
  • Bulbourethral glands

35
Male Reproductive PhysiologyAccessory Gland
Function
  • Seminal Fluid Components, Function and Location
    (source)
  • From Table 26-3

36
Male Reproductive PhysiologyThe sexual response
  • Remember
  • Function of the reproductive system is to
    reproduce
  • Males contribution is
  • Deliver viable sperm into the vagina
  • Requires a complex neural reflex the erection
    reflex
  • Creates changes in vascular condition within the
    penile arterioles
  • Initiated by erotic stimuli (visual, auditory,
    tactile, cerebral)
  • the parasympathetic division of the ANS causes
    vasodilation of the penile arterioles
  • Erectile tissue fills with blood creating an
    erection

37
Male Reproductive PhysiologyThe sexual response
  • Remember
  • Function of the reproductive system is to
    reproduce
  • Males contribution is
  • Deliver viable sperm into the vagina
  • Requires a complex neural reflexes
  • Starts with the erection reflex which creates
    changes in vascular condition within the penile
    arterioles
  • Initiated by erotic stimuli (visual, auditory,
    tactile, cerebral)
  • the parasympathetic division of the ANS causes
    vasodilation of the penile arterioles
  • Erectile tissue fills with blood creating an
    erection
  • Emission Ejaculation during climax
  • Emission is the movment of sperm from vas
    deferens into the urethra adding seminal fluid
    along the way, this is under sympathetic control
  • Ejaculation is the expulsion of semen due to
    strong muscular contractions this is a spinal
    reflex

38
Male Reproductive PhysiologyThe sexual response
  • Erection Reflex Pathway

39
Male Reproductive PhysiologyThe sexual response
  • Emission Ejaculation during climax
  • Emission is the movement of sperm from vas
    deferens into the urethra adding seminal fluid
    along the way, this is under sympathetic control
  • Ejaculation is the expulsion of semen due to
    strong muscular contractions this is a spinal
    reflex
  • Started with the contraction of the
    bulbospongiosus muscle
  • Disorders
  • Erectile dysfunction (ED)
  • Premature ejaculation
  • Prolonged ejaculation / anorgasmic

40
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