Sexual Reproduction in Humans - IGCSE Biology Revision Notes

Male Reproductive System

Structures and Functions

• Prostate gland: Produces semen to provide nutrients to sperm cells.
• Sperm duct: Passageway for sperm to mix with gland fluids before ejaculation.
• Urethra: Carries urine or semen; a muscle prevents mixing.
• Testis: Produces sperm and testosterone; contained in the scrotum.
• Scrotum: Supports testes outside body, maintaining lower temperature for sperm.
• Penis: Facilitates urination and semen transfer during intercourse.

Diagram

• Diagram illustrating male reproductive system components (not shown here).

Female Reproductive System

Structures and Functions

• Oviduct: Connects ovary to uterus, site of fertilization.
• Ovary: Contains and matures ova upon hormonal stimulation.
• Uterus: Site for embryo implantation and fetal development.
• Cervix: Muscle ring maintaining fetus position during pregnancy.
• Vagina: Muscular tube for semen reception during intercourse.

Diagram

• Diagram illustrating female reproductive system components (not shown here).

Gametes and Fertilization

Fertilization

• Fusion of nuclei from male (sperm) and female (egg) gametes.
• Occurs in the oviducts.
• Gametes have adaptations for successful fertilization and embryo development.

Adaptations of Gametes

Sperm

• Flagellum: Assists in swimming towards the egg.
• Enzymes (acrosome): Digest path to egg.
• Mitochondria: Provide energy for movement.

Egg

• Cytoplasm: Energy store for post-fertilization cell division.
• Jelly-like coating: Becomes impenetrable post-fertilization.

Comparison of Gametes

• Size: Sperm is small; egg is larger.
• Structure: Sperm has a head and tail; egg is round.
• Motility: Sperm is mobile; egg is not.
• Numbers: Sperm produced daily in millions; one egg released monthly.

Pregnancy: Growth and Development of the Fetus

• Zygote travels to uterus, dividing to form an embryo.

• Gestation period: 9 months.

  • Initial 12 weeks for organ development.
  • Placenta forms; embryo becomes fetus.
  • Remaining time for fetal growth.

• Amniotic sac: Cushions fetus with fluid.

• Umbilical cord: Connects fetus to placenta for nutrient exchange.

The Placenta and Umbilical Cord

Functions

• Facilitates nutrient and gas exchange between mother and fetus.
• Diffusion: Across placenta due to concentration gradients.
• Barrier: Prevents some toxins and pathogens from reaching the fetus.

Diagram

• Diagram illustrating placenta and umbilical cord structure (not shown here).

Important Notes

• Not all toxins/pathogens are blocked; pregnant women should avoid smoking due to nicotine passage.
• Exam tip: Know specific substances transferred across placenta for exams.