material from ma'am shiela

MALE REPRODUCTIVE SYSTEM

1. Main Structures & Their Functions

  • Testes

    • Seminiferous tubules: Site of sperm production (spermatogenesis).

    • Sertoli cells: Known as "nurse cells" that:

    • Nourish developing sperm.

    • Form blood-testis barrier, which protects sperm from the immune system.

    • Regulate spermatogenesis, the process by which sperm cells are produced.

    • Leydig cells: Produce testosterone, which contributes to male secondary sexual characteristics and regulates various functions in the male reproductive system.

  • Epididymis

    • Stores sperm and allows for maturation and development of motility necessary for fertilization.

  • Vas Deferens

    • Transports mature sperm from the epididymis to the urethra. Damage to this structure would result in an inability for sperm to exit the body.

  • Seminal Vesicles

    • Produce a fructose-rich fluid that serves as an energy source for sperm.

    • Contributes to 60% of semen volume.

  • Prostate Gland

    • Produces an alkaline fluid that neutralizes the acidity of the vagina, thereby increasing sperm viability and motility.

  • Bulbourethral (Cowper’s) Gland

    • Produces lubrication and cleans the urethra of acidic urine residue prior to ejaculation.

  • Urethra

    • Serves as the final passageway for sperm to exit the body.

  • Scrotum

    • Functions in temperature regulation, maintaining a temperature lower than body temperature, which is essential for optimal sperm production.

    • Failure in temperature regulation can lead to decreased sperm count and quality.

SPERM CELL STRUCTURE & FUNCTION

  • Head

    • Contains the nucleus with 23 chromosomes essential for genetic contribution during fertilization.

    • Acrosome: A cap-like structure that contains enzymes needed to penetrate the egg during fertilization.

  • Midpiece

    • Contains mitochondria, which produce energy (ATP) necessary for sperm motility.

  • Tail/Flagellum

    • Responsible for the movement and motility of the sperm; a defective tail results in an inability to reach and fertilize the egg.

FEMALE REPRODUCTIVE SYSTEM

1. Main Structures

  • Ovaries

    • Produce eggs (ova) and secrete hormones, including estrogen and progesterone.

  • Fallopian Tube

    • Site of fertilization, transporting the fertilized egg to the uterus.

    • A blockage here can prevent fertilization.

  • Uterus

    • The structure where implantation of the fertilized embryo occurs, supporting fetal development throughout pregnancy.

  • Cervix

    • During ovulation, the cervical mucus becomes thin and allows sperm entry.

    • During pregnancy, a thick mucus plug forms to protect the fetus.

    • During labor, the cervix must dilate to allow for passage of the baby.

MENSTRUAL CYCLE (28 DAYS)

A. Hormones

  • Hypothalamus → Releases Gonadotropin-releasing hormone (GnRH) which stimulates:

  • Pituitary Gland → Releases Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH):

    • FSH: Stimulates growth of ovarian follicles.

    • LH: Triggers ovulation and the formation of the corpus luteum.

  • Ovary → Produces Estrogen and Progesterone:

    • Estrogen: Thickens the endometrium in the proliferative phase of the menstrual cycle.

    • Progesterone: Maintains the endometrium during the secretory phase.

B. Phases

  1. Follicular Phase (Day 1–13)

    • FSH promotes the growth of follicles.

    • Rising levels of estrogen.

    • Cervical mucus becomes thin and watery, facilitating sperm passage.

  2. Ovulation (Day 14)

    • Triggered by a surge in LH.

    • The mature egg is released from the Graafian follicle.

  3. Luteal Phase (Day 15–28)

    • Corpus luteum produces progesterone.

    • If no pregnancy occurs, the corpus luteum degenerates into the corpus albicans.

SPERMATOGENESIS Process

  1. Spermatogonium (2n): The initial diploid germ cell in spermatogenesis.

  2. Primary spermatocyte (2n): Undergoes meiosis I to produce:

  3. Secondary spermatocyte: Results from meiosis I.

  4. Spermatid: Develops post-meiosis.

  5. Sperm cell: Final output via spermiogenesis.

Why Meiosis is Important?

  • Produces haploid gametes (n = 23) necessary for sexual reproduction.

  • Ensures genetic contribution from both parents (23 chromosomes from the mother and 23 from the father).

  • Increases genetic diversity in offspring.

OOGENESIS Process

  1. Oogonium (2n): The diploid germ cell in oogenesis.

  2. Primary oocyte (2n): Arrested in prophase I until puberty.

  3. Secondary oocyte + polar body: Generated after meiosis I.

  4. Ovulation: The secondary oocyte is released.

  5. Meiosis II: Only completed upon fertilization.

Why Only One Egg?

  • Resources are concentrated into one viable oocyte for effective nourishment of the embryo.

FERTILIZATION & IMPLANTATION

Fertilization

  • Occurs in the ampulla of the fallopian tube and requires sperm penetration of the Zona Pellucida surrounding the egg.

Implantation

  • Occurs within the uterine endometrium.

  • Correct location is vital to prevent ectopic pregnancy and to allow placenta formation.

PREGNANCY Stages

  • Zygote: The fertilized egg after union of sperm and egg.

  • Cleavage: Rapid cell division following fertilization.

  • Morula: A solid ball of cells formed from cleavage.

  • Blastocyst: The stage before implantation.

  • Implantation: Embedding of blastocyst in the endometrium.

  • Embryo: Early stage of development post-implantation.

  • Fetus: The developing organism after the embryonic stage.

  • Birth: The final stage of development.

Birth Canal Pathway

  • Pathway during childbirth is: Uterus → Cervix → Vagina.

SITUATIONAL QUESTIONS REVIEW

  • Temperature Regulation (Scrotum): High temperatures lead to decreased sperm count and quality, hindering fertility.

  • Blocked Fallopian Tubes: Prevent fertilization as the sperm cannot meet the egg.

  • Non-dilating Cervix: Can lead to difficult labor as the baby cannot pass through.

  • Corpus Luteum Fate:

    • If no pregnancy occurs, the corpus luteum degenerates.

    • If pregnancy occurs, it is maintained by human Chorionic Gonadotropin (hCG).

PATHWAYS TO REMEMBER

  • Sperm Pathway:
    Testis → Epididymis → Vas Deferens → Seminal Vesicle → Prostate → Urethra → Exit.

  • Hormone Pathway:
    Hypothalamus → GnRH → Pituitary Gland → FSH/LH → Ovary/Testes → Production of Gametes + Hormones.

  • Egg Pathway:
    Ovary → Fallopian Tube → Uterus.

Discussion of Understanding Each Phase

  • Helps with:

    • Fertility awareness and planning.

    • Timing intercourse for conception.

    • Avoiding pregnancy through natural family planning.

    • Recognizing hormonal imbalances.

    • Planning reproductive health decisions, including understanding ovulation cycles.

Overview of Menstrual Cycle Phases

  • Follicular Phase: Egg growth and preparation for ovulation.

  • Ovulation: The fertile window when conception is possible.

  • Luteal Phase: Possible implantation of a fertilized egg.

  • Proliferative Phase: The endometrium thickens in anticipation of embryo implantation.

  • Secretory Phase: The endometrium is maintained by progesterone.

  • Menstrual Phase: Shedding of the endometrial lining if no implantation occurs.