Female Reproductive System Overview

Overview of the Female Reproductive System

• The female reproductive system shares some similarities with the male reproductive system but includes distinct processes and structures.

  • Both systems have gonads, accessory reproductive organs, and external genitalia.

  • Gametes undergo oogenesis in females and spermatogenesis in males, showcasing differences in process and timing.

Gonadal Structures

• Female gonads: Ovaries

  • Size: Slightly larger than almonds.

  • Anchored in place by ligaments:

  • Ovarian ligament

  • Suspensory ligament

  • Associated with fallopian tubes

• Cross-section anatomy of the ovaries:

  • Medulla: Inner core of the ovary containing blood vessels and nerves.

  • Cortex: Outer layer containing follicles and oocytes.

Oocyte Development

• Number of oocytes available:

  • Fetal development: Approximately 7,000,000 oocytes.

  • At birth: Decreases to 1-2,000,000 oocytes.

  • Puberty (around age 13): Number decreases to about 400,000 oocytes.

• Oocyte Development Process:

  • Primordial follicles stay dormant until puberty.

  • Each month, approximately 20 follicles develop, but only one matures (the rest undergo atresia).

Folliculogenesis

• Stages of follicle development:

  • Primordial Follicle: Present at birth, contains primary oocyte.

  • Primary Follicle: Forms after puberty; remains in prophase I until ovulation.

  • Secondary Follicle: Begins development following hormonal stimulation.

  • Secretes estrogen influenced by interaction between thecal and granulosa cells, stimulated by FSH and LH.

  • Antral Follicle: Contains antrum filled with follicular fluid to aid in ovulation.

  • Mature Follicle: ovulates and releases secondary oocyte.

Oogenesis

• Oogenesis compared to spermatogenesis:

  • Begins with oogonium, undergoes mitosis to produce one primary oocyte (46 chromosomes) and one degenerated cell.

  • Primary oocyte starts meiosis but pauses in prophase I until puberty occurs.

  • At puberty, a selected primary oocyte completes meiosis I and begins meiosis II, stopping at metaphase II until fertilization happens.

Hormonal Regulation of Ovarian Cycle

• GnRH (Gonadotropin-Releasing Hormone): Secreted from the hypothalamus to stimulate the pituitary gland.

• Pituitary hormones:

  • FSH (Follicle-Stimulating Hormone): Stimulates follicle growth.

  • LH (Luteinizing Hormone): Triggers ovulation.

• Hormonal changes through the cycle:

  • Follicular phase lasts about 13 days followed by ovulation at day 14.

  • The luteal phase lasts about 14 days after ovulation.

Uterine Cycle

• Phases of the uterine cycle:

  • Menstrual Phase: Shedding of the functional layer of the endometrium due to hormonal changes (low progesterone).

  • Proliferative Phase: Regeneration of the endometrial lining under the influence of rising estrogen levels.

  • Secretory Phase: Maintained by progesterone produced by the corpus luteum; prepares the uterus for potential implantation.

Corpus Luteum Function

• The corpus luteum forms post-ovulation from remnants of the follicle and secretes progesterone and estrogen.

• If fertilization occurs, the corpus luteum is maintained for about three months by hormones from the embryo to support the endometrium.

• If no fertilization occurs, the corpus luteum degenerates, leading to a decrease in progesterone and triggering menstruation.

Menopause

• Occurs between ages 45-55; defined as one year without menstruation.

• Marked by a depletion of ovarian follicles, leading to decreased estrogen and progesterone production.

Estrogen and Progesterone Effects on the Uterus

• Estrogen: Stimulates growth and proliferation of endometrial tissue.

• Progesterone: Maintains endometrial thickness, prepares glands for nutrient secretion, and promotes vascularization.

External Female Reproductive Anatomy

• Structures:

  • Labia Majora: Homologous to the male scrotum; protects internal structures.

  • Labia Minora: Homologous to the shaft of the penis; contains sebaceous glands.

  • Clitoris: Homologous to the penis; contains erectile tissue, sensitive receptors.

  • Mammary glands: Develop in response to estrogen during pregnancy; produce milk post-partum.

Lactation

• Hormones involved:

  • Prolactin: Stimulates milk production.

  • Oxytocin: Ejects milk during breastfeeding.

• Importance of both hormones for lactation success.

Breast Cancer Risks

• Risk factors include family history, delayed childbirth, presence of BRCA genes, long exposure to estrogen, etc.

• Recommendations for self-examinations and mammograms starting at age 40 or earlier if risks are present.

Summary

• Comprehensive understanding of the female reproductive system involves the interplay of hormonal cycles, anatomy, and processes that govern reproductive health and functions.