Physiology 1 2003 Topic 10: Reproduction

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Physiology 12003Topic 10 Reproduction

• Ref Germann Stanfield (2002) Chapter 21

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Reproduction 2 Pages 683-694Objectives

• Explain cyclic levels in reproductive hormones
• Explain how reproductive hormones regulate
  changes in ovaries uterus

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Female Reproductive System

• Characteristics
• Cyclic
• Menstrual cycle 28 day variations in
  secretions of hormones from hypothalamus,
  anterior pituitary ovaries
• Restricted periods of fertility
• Within a few days of ovulation
• every 28 days
• Limited gamete production
• Ova present _at_ birth
• 1 ovum released per month ( 400 in lifetime)
  others degenerate

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Functional Anatomy of Female Reproductive Organs
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Female Reproductive System
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Female Reproductive System
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Ovaries

• Ovary contains numerous follicles.
• Primordial Follicle Oocyte surrounded by
  granulosa cells, which develop into theca cells
• Granulosa cells are protective, receptive to
  estrogen FSH secrete inhibin.
• Secrete estrogen (derived from theca cells)
  progesterone

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Reproductive Tract

• Uterus
• Cervix
• Myometrium outer layer of smooth muscle
• Endometrium inner layer of epithelial cells over
  a layer of connective tissue.
• Contains glands
• Vagina smooth muscle
• Uterine Tubes Cilia Fimbrae

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Female External Genitalia
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Ova Their Development

• Germ cells ? Oogonia --------? Primary oocytes
• Mitosis
• Division of diploid primary oocytes is arrested
  _at_ meiosis I during embryological development of
  the female
• Meiosis I resumes in 1 primary oocyte just prior
  to ovulation, producing a Secondary oocyte
  Polar body (degenerates)
• Meiosis II is completed after fertilization ?
  an Ovum (haploid) Polar body (degenerates)

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Oogenesis The Development of Ova
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Sexual Response in Females

• blood volume in some tissues eg clitoris
  nipples
• Vaginal secretions
• Pleasurable sensations
• Orgasm rhythmic contractions of vagina
  uterus, ?BP, HR skeletal muscular contractions
  

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Menstrual Cycle Involves

• Ovarian Cycle
• Follicular Phase Luteal Phase
• Uterine Cycle
• Menstrual Phase
• Proliferative Phase
• Secretory Phase

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Ovarian Cycle

• (i) Follicular Phase 14 days
• Some follicles develop
• Oocytes get larger
• Granulosa cells proliferate
• Zona Pellucida (non-cellular) forms
• Antrum - Fluid filled cavity forms
• Granulosa thecal cells produce estrogen
• Usually only 1 follicle completes dev. Others
  produce less estrogen undergo Atresia
• Oocyte detaches from follicle wall ? Graafian
  Follicle

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The Ovarian Cycle
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The Ovarian Cycle
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(ii) Luteal Phase

• Graafian follicle ruptures becoming a Corpus
  Luteum which secretes estrogens progesterone
• Oocyte is released into peritoneal cavity, swept
  into fallopian tubes by currents generated by
  cilia, then transported by peristalsis.
• If No Fertilization Corpus luteum degenerates
  into corpus albicans after 10 days
• ? Plasma estrogen progesterone ? Menstruation
• If Fertilization Corpus luteum persists

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Uterine Cycle(i) Menstrual Phase

• Degeneration of the corpus luteum
• ? Plasma estrogen progesterone ? blood vessels
  in endometrium constrict ? necrosis ? lining of
  endometrium sloughs off.
• (Endometriosis Uterine tissue which may develop
  elsewhere in peritoneal cavity by mistake, is
  under the same hormonal influences as the
  uterus.)

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The Uterine Cycle
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(ii) Proliferative Phase

• ? Plasma estrogens from growing follicle
  stimulate
• Endometrium regenerates, myometrium thickens,
  endometrial glands enlarge, blood vessels
  proliferate cervix secretes mucus.

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(iii) Secretory Phase

• ?Plasma progesterone from corpus luteum
  stimulates
• Blood vessels proliferate
• Endometrial glands secrete glycogen ? energy.
• Viscous cervical secretions plug the cervix -
  Seals body of uterus from bacteria.
• No fertilization ? corpus luteum degenerates ?
  ?Plasma progesterone ? Menstruation

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Hormonal Changes During the Menstrual Cycle

• Hormonal changes in the follicular luteal
  phases of the ovarian cycle influence the uterine
  cycle.
• Carefully Examine Figures 21.14 -15 together.
• Then relate them to Figures 21.16-18.
• You may need to do this several times to grasp
  the relationships.
• Note carefully the hormonal-induced changes in
  endometrial tissue eg Fig 21.14

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Hormonal Changes in the Early to Mid-Follicular
Phase

• GnRH ? anterior pituitary ? FSH LH
• FSH ? granulosa cell proliferation
• ? Follicle growth
• FSH converts some granulosa cells to theca cells
• LH ? theca cells ? androgens which granulosa
  cells convert to estrogens
• Estrogens FSH ? follicle growth
• Estrogens ? LH FSH secretion (-ve feedback)
• Granulosa cells ? Inhibin ? FSH secretion (-ve
  feedback)

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The Menstrual Cycle
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Regulation of hormone secretion during the early
to mid-follicular phase
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Hormonal Changes in the Late Follicular Phase

• ? Estrogens ?LH FSH secretion (ve feedback)
• ? Estrogens , FSH LH ie LH surge
• Estrogens ? LH receptors on granulosa cells
• LH? granulosa cells ? paracrines ? Meiosis
  resumes
• LH? Estrogens secretion by granulosa cells ?
• LH? granulosa cells ? Progesterone
• Ovulation Follicle wall ruptures
• Granulosa theca cells ? corpus luteum

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Regulation of hormone secretion during the late
follicular phase
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Hormonal Changes in the Luteal Phase

• Loss of follicle ? Estrogens
• ? Estrogens ? the ve feedback secretion of
  LH
• LH surge ends
• Corpus luteum ? Progesterone later Estrogens
• Progesterone inhibits LH FSH secretion
• Degeneration of corpus luteum after 10 days
• ? Progesterone Estrogen secretion
• ? Progesterone Estrogen ? Menstruation

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Regulation of hormone secretion during the luteal
phase
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Long-Term Hormonal Regulation of Female
Reproductive Function

• Estrogen Progesterone levels
• ? _at_ puberty (Read Table 21.2 for effects)
• Estrogen ? female secondary sex characteristics
  eg widening of hips, ? fat in breasts, hips
  buttocks, ? skin oil, ? pubic hair growth of
  bones
• Estrogen levels remain high, but? _at_ menopause,
  reversing the effects of puberty

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