Female Reproductive System

Female Reproductive Anatomy

  • Reproductive role in females is more complex due to pregnancy.

  • Ovaries: female gonads — produce ova; secrete estrogen and progesterone.

  • Internal genitalia: ovaries and duct system (uterine tubes, uterus, vagina).

  • External genitalia: external sex organs.

Ovaries

  • Ovaries held in place by ligaments; blood supply via ovarian arteries and ovarian branch of uterine arteries.

  • Two regions: cortex and medulla.

  • Ovarian follicles contain immature oocytes; follicles progress through developmental stages.

  • Ovulation: ejection of oocyte from ripening follicle.

  • Corpus luteum develops from ruptured follicle after ovulation.

The Female Duct System

  • Uterine tube system does not have direct contact with ovaries.

  • Ovulated oocyte is released into the peritoneal cavity; some oocytes do not reach the tube system.

  • Tube system includes: uterine tubes, uterus, and vagina.

The Uterus

  • Hollow, thick-walled, muscular organ.

  • Function: receive, retain, and nourish fertilized ovum.

  • Regions: body, fundus, isthmus, cervix, cervical canal.

  • Cervical canal communicates with vagina via the external os.

  • Cervical glands secrete mucus that blocks sperm entry except during midcycle.

The Vagina

  • Thin-walled tube; birth canal, passageway for menstrual flow, and organ of copulation.

  • Extends between bladder and rectum from cervix to exterior genitalia.

  • Vaginal secretions: acidic in adults; alkaline in adolescents.

  • Mucosa near vaginal orifice forms the hymen that ruptures with intercourse.

  • Vaginal fornix: upper end surrounding the cervix.

External Genitalia

  • Also called vulva or pudendum.

  • Components: Mons pubis; Labia majora; Labia minora; Vestibule.

Greater Vestibular Glands (External Genitalia)

  • Flank the vaginal opening; homologous to bulbourethral glands.

  • Release mucus into the vestibule for lubrication.

  • Clitoris: anterior to vestibule; Glans of clitoris (exposed); Prepuce of clitoris (hoods glans).

  • Perineum: Diamond-shaped region between pubic arch and coccyx; bordered by ischial tuberosities.

Mammary Glands

  • Present in both males and females but normally functional only in females.

  • Main function: milk production to nourish the newborn.

Oogenesis

  • Oogenesis: production of female gametes.

  • Begins in fetal period; primary oocytes begin meiosis but stall in an early phase.

  • At birth, female is presumed to have lifetime supply of primary oocytes.

  • Each month after puberty, a few primary oocytes are activated.

  • One from this group is selected to become the dominant follicle and resume meiosis I.

  • After meiosis I, two haploid cells are produced: a secondary oocyte and a first polar body.

The Ovarian Cycle

  • Ovarian cycle: ~2828-day series of events associated with egg maturation.

  • Two consecutive phases with ovulation midcycle (around day 1414):

    • Follicular phase: growth of vesicular (follicle) follicles (days 1−141-14).

    • Luteal phase: corpus luteum activity (days 14−2814-28).

  • Only 10−15%10-15\% of women have a 28-day cycle.

  • Follicular phase length varies; luteal phase is always 1414 days from ovulation to the end of the cycle.

Luteal Phase of the Ovarian Cycle

  • After ovulation, ruptured follicle collapses.

  • Remaining granulosa and internal thecal cells enlarge to form the corpus luteum.

  • Corpus luteum secretes progesterone and some estrogen.

  • If no pregnancy occurs, corpus luteum degenerates into corpus albicans in 1010 days.

  • If pregnancy occurs, corpus luteum persists to sustain pregnancy until placenta takes over at about 3 months3\text{ months}.

Regulation of Female Reproductive System

  • Hormonal Regulation of Ovarian Cycle: Establishing the ovarian cycle

    • Before puberty, ovaries secrete small amounts of estrogen, inhibiting hypothalamic GnRH release.

    • As puberty nears, GnRH is released, stimulating FSH and LH release by the pituitary, which act on the ovaries.

    • Events continue until an adult cyclic pattern is achieved and menarche occurs.

Hormonal Regulation of Ovarian Cycle (Detailed)

  • 1. GnRH stimulates FSH and LH secretion.

  • 2. FSH and LH stimulate follicles to grow, mature, and secrete sex hormones.

  • 3. Negative feedback inhibits gonadotropin release.

  • 4. Positive feedback stimulates gonadotropin release.

  • 5. LH surge triggers ovulation and formation of the corpus luteum.

  • 6. Negative feedback inhibits LH and FSH release.

The Uterine (Menstrual) Cycle

  • Uterine (menstrual) cycle: cyclic changes in the endometrium in response to fluctuating ovarian hormone levels.

  • Phases:

    • Days 1−51-5: menstrual phase.

    • Days 6−146-14: proliferative (preovulatory) phase.

    • Days 15−2815-28: secretory (postovulatory) phase.