Female Reproductive System Notes

Female Reproductive System

Functions

  • Produce female gametes (oocytes).
  • Produce sex steroid hormones (estrogen/progesterone).
  • Receive male gametes.
  • Allow pregnancy, nourish/develop embryo/fetus.
  • Nourish infant via lactation.
  • Begins prior to birth.
  • Site of fertilization.
  • Site of implantation (uterus).
  • Allow birth of baby.

Oogenesis

  • Production of gametes (oocytes).

Reproductive Organs: Ovaries

  • Held in place by:
    • Broad ligament
    • Suspensory ligament
    • Ovarian ligament

Hormone Production

  • Estrogen
  • Progesterone
  • Inhibin
  • Relaxin

Number of Oocytes

  • At birth: 200,000-2 million
  • At puberty: ~40,000
  • Oocytes in ovary are seen as follicles: follicular cells + oocyte.

Ovarian Cycle

  • Typically 28 days of reproductive cycle.
  • Day 1 = 1st day of menstruation

Hormones Involved

  • FSH (Follicle Stimulating Hormone)
  • LH (Luteinizing Hormone)

Follicular Phase (Day 1-14)

  • FSH stimulates the growth of follicles (2mm).
Follicle Development
  • Oocyte + Follicular cells = Primordial Follicle
  • Zona pellucida formation occurs.
  • FSH converts primordial follicle into primary follicle.
  • Granulosa cells produce:
    • Estrogen
    • Antral fluid
    • Inhibin
  • Dominant follicle will inhibit all other follicles from developing.
  • Antrum
  • The dominant follicle becomes a secondary follicle.
  • Follicles develop at different rates.

Ovulation (Day 14)

  • Granulosa cells increase in number.
  • Estrogen production increases in follicle.
  • Graafian follicle present.
  • Normally, low levels of estrogen have (-) feedback on hypothalamus & anterior pituitary.
  • High estrogen levels cause (+) feedback on anterior pituitary to cause LH surge.
Graafian/Mature Follicle
  • Zona pellucida
  • Corona radiata - layer of granulosa cells

LH Surge

  • Level of LH increases
  • Completes Meiosis I (1° oocyte → 2° oocyte, halted in metaphase II).
  • Causes rupture (expulsion) of oocyte = Ovulation (occurs on day 14).
  • Ovulation detector kits test for presence of LH (LH surge leads to ovulation).
Mittelschmerz
  • Mid-cycle pain during ovulation felt in some females.

Luteal Phase (Day 15-28)

  • Only visible for 2 weeks (only if pregnancy occurs).
  • 14 days (roughly)
  • LH converts ruptured follicular cells into luteal cells
  • Granulosa cells form Graafian follicle becomes Corpus hemorrhagicum (bloody).
  • Corpus luteum, cholesterol is converted into progesterone, which cells becomes hormone producing factory.
Hormones Produced by Corpus Luteum

  • Progesterone (main)

  • Estrogen (some)

  • Inhibin (prevents FSH)

  • Relaxin (relaxes uterus)

  • If no fertilization, corpus luteum becomes Corpus Albicans (white) after 2 weeks.

Role of hCG
  • If fertilization/implantation occurs, syncytiotrophoblast cells secrete hCG (Human Chorionic Gonadotropin).
  • Presence of hCG indicates implantation (pregnancy).