Female Reproduction

Female Reproductive Anatomy

  • Suspensory Ligament of Ovary: Connects ovaries to the lateral pelvic wall.

  • Uterine (Fallopian) Tube: Pathway for ova from the ovary to the uterus.

    • Ovarian Blood Vessels: Supply blood to the ovaries.

    • Broad Ligament: Supports the uterus and contains the mesosalpinx (the part of the broad ligament that encloses the uterine tubes).

  • Mesosalpinx: Part of the broad ligament associated with the uterine tubes.

  • Fundus of Uterus: The upper portion of the uterus.

  • Ovary: Female reproductive organ that produces ova and hormones.

  • Lumen (Cavity) of Uterus: The interior space of the uterus where the embryo implants.

  • Uterine Tube: Transports the egg from the ovary to the uterus.

    • Ampulla: The widest part of the uterine tube; common site of fertilization.

    • Isthmus: The narrowest part of the uterine tube, connecting to the uterus.

    • Infundibulum: Funnel-shaped structure that ends with fimbriae surrounding the ovary.

  • Fimbriae: Finger-like projections that help guide the ovum into the uterine tube.

  • Round Ligament of Uterus: Supports the uterus and maintains its position in the pelvis.

  • Wall of Uterus:

    • Endometrium: Inner lining of the uterus; thickens during the menstrual cycle.

    • Myometrium: Muscular middle layer of the uterine wall.

    • Perimetrium: Outermost layer of the uterus.

  • Internal Os: The opening of the cervix into the uterus.

  • Cervical Canal: The channel within the cervix.

  • External Os: The opening of the cervix into the vagina.

  • Mesovarium: Fold of peritoneum that connects the ovaries to the broad ligament.

  • Mesometrium: Part of the broad ligament that supports the uterus.

  • Ovarian Ligament: Connects the ovary to the lateral pelvic wall.

  • Body of Uterus: The main part of the uterus.

  • Ureter: Tube carrying urine from the kidney to the bladder.

  • Uterine Blood Vessels: Supply blood to the uterus.

  • Uterosacral Ligament: Connects the cervix to the sacrum, supporting the uterus.

  • Cardinal (Lateral Cervical) Ligament: Supports the cervix and aids in uterine support.

  • Lateral Fornix: The recess around the cervix in the vagina.

  • Cervix: The lower part of the uterus that opens into the vagina.

  • Vagina: The muscular tube that connects the external genitals to the uterus.

Female Reproductive Cycle

  • Monthly hormone fluctuations result in:

    1. Ovarian Cycle: Involves egg maturation (oogenesis) and ovulation.

    2. Uterine (Menstrual) Cycle: Changes in the endometrium in response to hormonal fluctuations.

  • Cycle Duration: Approximately 24-35 days.

Ovarian Cycle

Occurrences in Ovaries

  • Oogenesis: The process of egg formation.

    • Involves diploid stem cells called oogonia that undergo differentiation before haploid eggs are produced.

    • Each oogonium produces one large haploid egg (ovum), which supplies initial nutrients for the zygote/embryo.

Arrested Development at Birth

  • Ova are arrested at birth, remaining in the prophase I stage of meiosis as primary oocytes (1° oocytes).

  • 1° oocytes are surrounded by a single layer of cells called follicular cells, forming a primordial follicle.

Follicle Development Over Time

  • At birth: approximately 1 million primary oocytes; by puberty: around 400,000.

  • Follicles begin developing slowly from fetal life, undergoing atresia (degeneration).

  • With the onset of puberty, some follicles are “rescued” monthly under hormonal influence.

  • Only one follicle matures fully and ruptures, releasing the ovum.

Phases of Ovarian Cycle

  1. Follicular Phase:

    • A batch of follicles starts maturing each month under hormonal influence.

    • Generally, only one follicle fully matures and releases an egg (ovulation); others degenerate.

    • The length of this phase is variable, explaining differences in women's cycle lengths.

  2. Luteal Phase:

    • Begins with ovulation.

    • The ruptured follicle becomes the corpus luteum, which produces hormones.

    • This phase is consistently 14 days long.

Follicular Maturation Processes

  • Follicular cell layers proliferate into multiple layers known as granulosa cells.

  • The formation of a connective tissue layer called theca folliculi (thecal cells) occurs.

  • Development of an antrum (fluid-filled cavity) is also involved in the process.

Changes in Follicle Types

  • Primordial Follicle: Contains primary oocyte and follicular cells.

  • Primary Follicle: Follicular cells begin to multiply.

  • Secondary Follicle: Antrum starts to form, and granulosa cells continue to develop.

  • Mature (Graafian) Follicle: Enlarged follicle with antrum ready to ovulate.

  • Corpus Luteum: Forms from a ruptured follicle, secreting hormones like progesterone and estrogens.

  • Corpus Albicans: Results from the degradation of the corpus luteum, fibrous tissue replaces it.

Female Sex Hormones

  • Estrogens: Includes estradiol, estrone, and estriol.

    • Secreted by ovaries; secretion increases at puberty.

    • Stimulates development and maintenance of accessory reproductive organs.

  • Progesterone: Also secreted by ovaries.

    • Promotes uterine changes during the reproductive cycle.

    • Regulates secretions of gonadotropins from the pituitary gland.

Hormonal Control of Reproduction

  • GnRH (Gonadotropin-releasing Hormone): Stimulates the release of FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone).

  • FSH: Promotes maturation of ovarian follicles.

    • Works alongside LH in stimulating follicles to release estrogens.

  • Rising levels of estrogens prevent FSH release through negative feedback.

  • Inhibin, released by granulosa cells, also exerts negative feedback on FSH.

Ovulation

  • Around day 14 of the cycle, the mature follicle releases high estrogen levels, creating a positive feedback loop promoting GnRH and LH release from the anterior pituitary.

  • LH Surge: Triggers ovulation, lasting approximately 36 hours.

Post-Ovulation Hormonal Changes

  • LH stimulates the ruptured follicle to develop into the corpus luteum, producing progesterone and estrogens.

  • These hormones promote uterine wall development and inhibit LH and FSH release.

  • If no fertilization occurs, the corpus luteum breaks down to form the corpus albicans.

Uterine Cycle Changes

  • The endometrium becomes thick and vascularized due to:

    • Estrogens during the follicular phase.

    • Estrogens and progesterone during the luteal phase.

  • Menstruation: Occurs when the corpus luteum degenerates into the corpus albicans, leading to a decline in progesterone and estrogen levels and the sloughing off of the endometrial lining.

    • First day of menstruation marks the beginning of the new cycle.

  • Prostaglandins: Hormones secreted by tissues related to inflammation control blood flow and clotting; within the menstrual cycle, they cause endometrial death leading to cramps.

Related Terms

  • Menarche: The first menstrual period.

  • Menopause: The end of menstruation.

  • Amenorrhea: Lack of menstruation.

Fertilization and Pregnancy

  • If fertilization occurs, the chorion membrane surrounding the embryo produces human chorionic gonadotropin (HCG).

    • HCG maintains the corpus luteum, continuing the production of progesterone and estrogen necessary to sustain pregnancy.

    • After the first three months, the placenta takes over hormone production.

  • Home Pregnancy Tests: Detect HCG in urine and confirm pregnancy.

Birth Control Pills (Oral Contraceptives)

  • Most contain a combination of estrogen and progesterone.

    • Provides negative feedback throughout the month, preventing an LH surge and subsequent ovulation.