Sexual Reproduction in Humans - IGCSE Biology Revision Notes

The Male Reproductive System

Structures

• Prostate Gland: Produces seminal fluid providing nutrients to sperm.
• Sperm Duct: Carries sperm to mix with glandular fluids before ejaculation.
• Urethra: Tube for urine or semen; muscle ring prevents mixing.
• Testis: Produces sperm and testosterone; located in the scrotum.
• Scrotum: Sac holding testes; maintains lower temperature for sperm.
• Penis: Excretes urine and introduces semen into the female during intercourse.

Diagram

• Visual representation of the male reproductive structures.

The Female Reproductive System

Structures

• Oviduct (Fallopian Tube): Connects ovaries to the uterus; site of fertilization; lined with cilia.
• Ovary: Contains and matures ova.
• Uterus: Muscular cavity for fetus development post-implantation.
• Cervix: Maintains fetus in place during pregnancy.
• Vagina: Muscular tube for intercourse and sperm reception.

Diagram

• Visual representation of the female reproductive structures.

Gametes & Fertilization

Key Concepts

• Fertilization: Fusion of sperm and egg nuclei, occurs in oviducts.
• Gametes have adaptations to improve fertilization success.

Gamete Adaptations

• Sperm:
  • Flagellum (tail) for movement.
  • Enzymes in acrosome to penetrate egg.
  • Mitochondria for energy.
• Egg:
  • Energy stores in cytoplasm.
  • Protective jelly coating changes post-fertilization to block further sperm.

Comparison

• Sperm: Small, motile, produced in large numbers.
• Egg: Larger, not motile, produced less frequently.

Pregnancy: Growth & Development of the Fetus

• Post-fertilization, zygote travels to uterus, becomes embryo.
• Gestation lasts 9 months; major organ development within first 12 weeks.
• Embryo receives nutrients via diffusion before placenta formation.
• Fetus grows after organ formation; placenta supports nutrient/waste exchange.
• Amniotic sac and fluid protect fetus; umbilical cord connects fetus to placenta.

The Placenta & Umbilical Cord

Functions

• Fetus gains nutrients (glucose, amino acids, fats, oxygen) from the mother.
• Blood exchange in placenta prevents mixing; umbilical cord links fetal blood.
• Placenta removes waste (carbon dioxide, urea) from fetal blood.
• Diffusion of substances across placenta, aided by a large surface area and thin walls.

Toxins and Pathogens

• Placenta acts as a barrier, though some toxins/pathogens can pass (e.g., nicotine, certain viruses).
• Importance of avoiding smoking during pregnancy to protect fetal health.

Exam Tips

• Know specific substances that exchange between mother and fetus.

Diagram

• Visual representation of placenta and umbilical cord.

Conclusion

• Understanding the reproductive systems, processes of fertilization, and fetal development is crucial for IGCSE Biology.
• Detailed knowledge of adaptations, structures, and pregnancy stages ensures a comprehensive grasp of human reproduction.