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

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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

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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

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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

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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

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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!
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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)

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The BasicsGametogenesis
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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?
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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?
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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.

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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)

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The BasicsGender Determination

• Effects of SRY on sex organ development

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The BasicsGender Determination

• Indirect effects of SRY on male and female
  genital development

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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

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The Pituitary-Gonad Axis
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Lecture Outline

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

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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

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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

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Female Reproductive PhysiologyThe Cycles

• Hormonal control of the ovarian cycle

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Female Reproductive PhysiologyThe Cycles

• Hormonal control of the uterine cycle

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Female Reproductive PhysiologyAll together
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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

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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.

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Female Reproductive PhysiologyOne Possible
Outcome
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Female Reproductive PhysiologyOr.
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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

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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

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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

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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

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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

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Male Reproductive PhsyiologyTestes
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Male Reproductive PhysiologyTestes

• Spermatogenesis Hormonal Control Flow Chart

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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

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Male Reproductive PhysiologyAccessory Gland
Function

• Seminal Fluid Components, Function and Location
  (source)
• From Table 26-3

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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

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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

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Male Reproductive PhysiologyThe sexual response

• Erection Reflex Pathway

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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

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