Reproductive Biology BI399

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Reproductive BiologyBI-399

• Lecture 7
• Female reproductive anatomy

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Female reproductive system

• Function
• Production of ovum (pl. ova) (oogenesis) and
  release of oocytes (ovulation)
• Ovaries
• Production of sex steroid hormones (estrogens)
• Serves as a site or fertilization (oviduct) and
  implantation (uterus)

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General anatomy of mammalian female reproductive
system
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Female reproductive tract

• Paramesonephric duct (Müllerian duct) is probably
  derived from a ridge in the lining of
  dorsolateral body wall
• Its origin is different from archinephric
  (mesonephric or Wolffian) duct
• In mammals, paramesonephric duct is devoted
  exclusively to reproductive function (as is the
  case for most vertebrates)

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Female reproductive tract

• Ostium
• Opening to tubal portion
• Fimbriae
• fingers
• Infundibulum
• Ciliary beating to create current
• Sweeps ova into tube
• Oviduct (Fallopian tube)
• Cite of fertilization
• More on this later

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Female reproductive tract

• Uterus
• Site of implantation
• Endometrium
• Glandular portion
• Myometrium
• Muscular portion
• Cervix
• Muscular sphincter
• Vagina

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Human reproductive anatomy - female
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Ovaries

• Macroscopic anatomy
• In humans and most other mammals, paired organs
  situated in the dorso-lateral aspect of the
  abdominal cavity
• About 3 cm x 1 cm x 1.5 cm
• Ovarian surface is smooth in prepubertal animals,
  but becomes scarred and pitted from the release
  of ova after reaching puberty

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Ovaries

• Microscopic anatomy
• General structures
• Cortex
• Medulla
• Granulosa cells
• nourish ova and produce estrogen
• Theca cells (theca folliculi)
• produce androgen
• often with two layers
• theca externa or interna

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Ovary
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Oocyte Maturation

• Primary Oocyte
• dipoid 2N
• humans have 46 chromosomes
• 23 homologous pairs
• each pair includes one chromosome contributed
  from maternal and 1 from paternal parent
• arrested in prophase of meiosis I
• 99.9 of ovarian oocytes

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Oocyte Maturation

• Reduction division (finish Meiosis I)
• Equal division of homologous pairs, but unequal
  division of cytoplasm
• only occurs in germ cells
• First polar body
• Haploid 1N
• Secondary Oocyte
• Haploid - ovulated as it begins Meiosis II, then
  arrested
• Meiosis II
• stimulated by sperm penetration
• 2nd polar body
• Ootid

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Oogenesis
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Follicular development in human ovaries

• Follicular phase
• About 10-14 days in human
• From before birth to end of reproductive years,
  the ovarian cortex contains thousands of
  primordial follicles
• Single oocyte surrounded by a thin layer of
  follicular cells
• At the start of each cycle, 6-12 follicles start
  to grow, depending on hormonal stimulation
• Become primary follicles

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Ovarian follicles
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Follicular development in human ovaries

• Primary follicles grow bigger to form a
  stratified layer of follicular cells surrounding
  the oocyte
• Forms granulosa cells.
• Oocyte develops acellular, glycoprotein coat
• zona pellucida
• Theca cells differentiate
• Theca externa
• Theca interna

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Follicular development in human ovaries

• Secondary follicle (2)
• Up to six layers of granulosa cells
• Cell divisions by mitosis
• Tertiary follicle (3)
• A clear liquid gathers between granulosa cells
  and form an antrum
• Oocyte sorrrounded by corona radiata
• Gaafian follicle (pre-ovulatory follicle)
• Cumulus oophorus
• A stalk of granulosa cells holding oocyte to the
  follicle
• High levels of estrogen are being produced
• Corpus luteum (CL)

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Ovarian follicles
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Ovarian follicles
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Follicle maturation
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Follicular development

• Follicular Atresia
• A female (any mammal) is born with all the
  oocytes she'll ever have
• Human embryo has 3.5 million follicles
• Fish, amphibians, reptiles and birds have
  germinal beds
• Can produce 1 oocytes throught life
• Produced mitotically, mature to ova meiotically
• Most follicles are lost by atresia
• Can happen at any stage
• More prevalent at later, larger stages
• Atresia often occurs as a result of supporting
  (steroidally) the follicle which will ovulate

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Atresia

• Follicular selection
• Very few oocytes are ovulated
• Larger follicles, with a greater blood supply,
  get a greater share of gonadotropins
• grow faster
• Which oocytes begin to grow are probably
  controlled by the hypothalamus via the vagus
  nerve
• Many follicles grow and then die
• Those that grow and do not ovulate help make
  steroids (E2) for positive feedback