Reproduction and Fertility

Reproductive Structures

  • Male Reproductive System

    • Testes: Produce sperm.

    • Sperm Tube: Carries sperm from the testes to the urethra.

    • Prostate Gland: Adds fluid to nourish sperm.

    • Urethra: Tube through which sperm leaves the penis.

    • Scrotum: Sac that holds and protects the testes, maintaining a slightly lower temperature than the body for optimal sperm production.

    • Penis: Organ that introduces sperm into the vagina.

  • Female Reproductive System

    • Ovaries: Produce ova (eggs).

    • Oviducts: Carry the ova to the uterus where fertilization occurs.

    • Uterus: Nourishes the developing fetus.

    • Cervix: Opening of the uterus, widens during childbirth.

    • Vagina: Receives sperm during intercourse.

Sperm Formation and Pregnancy

  • Sperm Cells: Specialized cells formed by meiosis, adapted to fertilization with a haploid nucleus, mitochondria for energy, and a flagellum for swimming.

  • Fertilization: Occurs in the oviduct when a haploid sperm nucleus fuses with a haploid egg nucleus to create a diploid zygote.

  • Zygote Development: The zygote divides by mitosis many times, forming a ball of cells (embryo) as it travels to the uterus.

  • Implantation: The embryo implants in the uterine lining and differentiates into tissues and organs.

  • Placenta: Adapted for nutrient exchange between mother and fetus via diffusion, featuring a large surface area and villi that facilitate this process.

  • Amniotic Fluid: Cushions the fetus within the amniotic sac.

Hormones

  • Sex Hormones:

    • Testosterone: Produced by testes, responsible for male secondary sexual characteristics.

    • Oestrogen: Produced by ovaries, responsible for female secondary sexual characteristics and menstrual cycle regulation.

    • Progesterone: Maintains the endometrium and prepares the uterus for potential pregnancy.

Menstrual Cycle

  • Duration: Approximately 28 days, from puberty until menopause (age 45-55).

  • Phases:

    • Menstruation (Days 1-5): Shedding of uterine lining.

    • Follicular Phase (Days 6-13): Uterine lining rebuilds, preparing for fertilization.

    • Ovulation (Day 14): Release of an egg from the ovary.

  • Hormonal Control: Oestrogen and progesterone regulate this cycle, promoting ovulation and preparing the uterine lining.

Infertility and Treatments

  • Causes of Infertility:

    • Females: Ovary failure, blocked oviducts, non-developing uterus lining.

    • Males: Low sperm count, impotence.

  • Treatments:

    • Fertility Drugs: Stimulate egg production.

    • In Vitro Fertilization (IVF): Eggs collected, fertilized in a lab, and embryos transferred to the uterus.

Contraceptive Methods

  • Mechanical:

    • Condoms: Prevent sperm entry; protect against STIs but can fail if improperly used.

  • Chemical:

    • Contraceptive Pill: Regulates hormone levels to prevent ovulation; potential side effects.

    • Implants: Long-term hormonal release; reliable but does not protect against STIs.

  • Surgical:

    • Vasectomy: Male sterilization; virtually 100% reliable but difficult to reverse.

    • Female Sterilization: Prevents ova from moving through oviducts; virtually 100% reliable but difficult to reverse.