Male and Female Reproductive System Flashcards

Overview of the Reproductive Systems

• Primary Sex Organs:

  • Males: Testes

  • Females: Ovaries

• Function:

  • Produce gametes (sperm and oocytes)

  • Secrete sex hormones: testosterone (males), estrogen and progesterone (females)

Male Reproductive System

• Gross Anatomy:

  • Testes: Primary site for spermatogenesis (sperm production) and testosterone production.

  • Duct System: Epididymis → Vas deferens → Ejaculatory duct → Urethra

  • Accessory Glands:

    • Seminal vesicles: Contribute to seminal fluid.

    • Prostate gland: Contributes to seminal fluid.

    • Bulbourethral glands (Cowper's glands): Produce a lubricating mucus secretion.

  • External Genitalia: Penis

• Microscopic Anatomy of Testes:

  • Seminiferous Tubules:

    • Contain spermatogenic cells (various stages of sperm development).

    • Sertoli cells (sustentacular cells): Support and nourish developing sperm cells.

  • Leydig Cells (Interstitial Cells):

    • Located outside the seminiferous tubules.

    • Secrete testosterone.

• Spermatogenesis:

  • Process of sperm production in the seminiferous tubules.

  • Sequence of Events:

    • Spermatogonia (stem cells) → Primary spermatocyte → Secondary spermatocyte → Spermatid → Spermatozoa (mature sperm)

  • Hormonal requirements:

    • Requires Follicle Stimulating Hormone (FSH) and testosterone.

  • Duration: Approximately 64-72 days.

• Hormonal Regulation in Males:

  • Hypothalamus:

    • Releases Gonadotropin-Releasing Hormone (GnRH).

  • Anterior Pituitary:

    • GnRH stimulates the release of:

      • FSH (Follicle-Stimulating Hormone): Stimulates Sertoli cells to support spermatogenesis.

      • LH (Luteinizing Hormone): Stimulates Leydig cells to produce testosterone.

  • Testosterone:

    • Promotes spermatogenesis.

    • Development of secondary sexual characteristics.

    • Negative feedback on GnRH, FSH, and LH secretion to maintain stable testosterone levels.

Female Reproductive System

• Gross Anatomy:

  • Ovaries: Site of oocyte development and hormone production.

  • Fallopian Tubes (Oviducts):

    • Fimbriae: Finger-like projections that sweep the oocyte into the tube.

    • Ampulla: Usual site of fertilization.

    • Isthmus: Connects to the uterus.

  • Uterus: Site of implantation and fetal development.

  • Cervix: Lower, narrow portion of the uterus.

  • Vagina: Connects the uterus to the external environment.

• Microscopic Anatomy of Ovaries:

  • Ovarian Follicles:

    • Primordial follicles → Primary follicles → Secondary follicles → Graafian follicle (mature follicle ready for ovulation)

    • Follicles contain the developing oocyte and follicular cells.

  • Corpus Luteum:

    • Forms after ovulation from the remnants of the Graafian follicle.

    • Secretes progesterone and estrogen.

  • Endometrium (Uterine Lining):

    • Functional layer: Responds to hormone changes and is shed during menstruation.

    • Basal layer: Regenerates the functional layer.

• Oogenesis:

  • Process of oocyte (egg) production in the ovaries.

  • Begins prenatally:

    • Oogonia (stem cells) undergo mitosis.

    • Primary oocytes begin meiosis but arrest in prophase I.

  • Each Cycle (after puberty):

    • Meiosis I is completed, resulting in a secondary oocyte and a polar body.

    • The secondary oocyte is ovulated and arrested in metaphase II.

    • Meiosis II is only completed if fertilization occurs.

• Hormonal Regulation in Females:

  • Hypothalamus:

    • Releases Gonadotropin-Releasing Hormone (GnRH).

  • Anterior Pituitary:

    • GnRH stimulates the release of:

      • FSH (Follicle-Stimulating Hormone): Stimulates follicle development in the ovary.

      • LH (Luteinizing Hormone): Triggers ovulation (release of the secondary oocyte).

  • Estrogen:

    • Produced by developing follicles.

    • Promotes endometrial growth and development.

    • Development of secondary sexual characteristics.

  • Progesterone:

    • Produced by the corpus luteum.

    • Maintains the endometrium to prepare for implantation.

Menstrual Cycle (Uterine Cycle)

• Cyclical changes in the endometrium of the uterus.

• Menstrual Phase (Days 1-5):

  • Shedding of the functional layer of the endometrium (menstruation).

  • Triggered by a drop in estrogen and progesterone levels.

• Proliferative Phase (Days 6-14):

  • Endometrial growth and thickening.

  • Driven by estrogen produced by the developing ovarian follicles.

• Ovulation (Around Day 14):

  • Release of the secondary oocyte from the Graafian follicle.

  • Triggered by a surge in LH (Luteinizing Hormone).

• Secretory Phase (Days 15-28):

  • Endometrium becomes more vascular and glandular.

  • Progesterone, produced by the corpus luteum, dominates this phase.

  • Prepares the endometrium for implantation.

  • If fertilization does not occur, the corpus luteum degenerates, and hormone levels drop, leading back to the menstrual phase.

Fertilization and Early Development

• Fertilization:

  • Occurs in the ampulla of the fallopian tube.

  • Acrosomal Reaction: Enzymes released from the sperm's acrosome digest the zona pellucida surrounding the oocyte.

  • Sperm and oocyte membranes fuse, leading to fertilization.

• Zygote Formation:

  • Fertilized egg (diploid cell).

• Cleavage:

  • Rapid mitotic cell divisions without cell growth.

  • Zygote → Morula (solid ball of cells).

• Blastocyst Formation:

  • Morula develops into a blastocyst (hollow ball of cells).

• Implantation:

  • Blastocyst implants into the endometrium of the uterus.

Puberty and Secondary Sexual Characteristics

• Male:

  • Testosterone-driven changes:

    • Development of facial hair.

    • Voice deepening.

    • Increased muscle mass.

• Female:

  • Estrogen-driven changes:

    • Breast development.

    • Pelvic widening.

    • Menarche (first menstrual period).

Clinical Correlations

• Polycystic Ovary Syndrome (PCOS):

  • Hormonal imbalance leading to ovarian cysts, irregular periods, and infertility.

• Endometriosis:

  • Presence of ectopic endometrial tissue outside the uterus, causing pain and potential infertility.

• Erectile Dysfunction:

  • Inability to achieve or maintain an erection, often due to blood flow or nerve supply issues.

• Testicular/Prostate Cancer:

  • Common cancers in men.

• Sexually Transmitted Infections (STIs):

  • Can impact fertility in both males and females.

• Infertility:

  • Can be caused by hormonal imbalances or structural abnormalities in either partner.

• Ectopic Pregnancy:

  • Implantation of the blastocyst outside the uterus (e.g., in the fallopian tube), which is a life-threatening condition.