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Cambridge IGCSE Biology · 0610

Chapter 16: Reproduction (Part 2)

Human reproductive systems

Male system
Includes testes (sperm and testosterone production), scrotum (holds testes), sperm ducts (transport sperm), prostate gland (secretes nutritive fluid for semen), urethra, and penis.
Female system
Includes ovaries (egg production), oviducts (site of fertilisation; contain cilia), uterus (where the foetus develops), cervix (holds the baby in place), and vagina.
Human male and female reproductive systems with labelled organs
Diagram 1: Human male and female reproductive systems. Clear labels of all organs mentioned above in their correct anatomical positions.

Exam Traps

  • Do not say fertilisation takes place in the uterus or vagina.
  • Avoid confusing the prostate gland (nutritive fluid for semen) with the testes (sperm production).

Human gametes

Sperm adaptations
Have a flagellum (tail) for movement, many mitochondria for energy, and enzymes in the acrosome to digest the egg wall.
Egg adaptations
Much larger than sperm; contain energy stores for early development; have a jelly coat that changes after fertilisation to prevent further sperm entry.

Exam Traps

  • Do not say the egg has a flagellum or that sperm store energy for early embryo development.
  • Avoid placing acrosome enzymes in the egg rather than the sperm.

Fertilisation and development

  1. Fertilisation: Fusion of sperm and egg nuclei in the oviduct.
  2. Implantation: The zygote divides (mitosis) to form an embryo (ball of cells), which implants into the uterus lining.
  3. Support structures:
    • Amniotic sac/fluid: Protects the foetus from physical damage.
    • Placenta: Facilitates exchange of nutrients (oxygen, glucose, amino acids, antibodies) and waste (carbon dioxide, urea) between mother and foetus via diffusion.
    • Pathogens: Some toxins (nicotine) and pathogens (rubella virus) can cross the placenta.

Exam Traps

  • Do not say the placenta is impermeable to all pathogens — some can cross.
  • Avoid confusing implantation (embryo into uterus lining) with fertilisation (in the oviduct).

Sex hormones and the menstrual cycle

Puberty
Testosterone (males) and oestrogen (females) regulate secondary sexual characteristics.
The menstrual cycle
A roughly 28-day cycle where an egg is released and the uterus lining thickens.
Hormonal control
  • FSH: Triggers egg development and oestrogen production.
  • Oestrogen: Thickens the uterus lining and stimulates LH.
  • LH: Triggers ovulation (egg release) and progesterone production.
  • Progesterone: Maintains the uterus lining; levels drop if the egg is not fertilised, leading to menstruation.

Examiner Report Insights

  • State the hormone sequence clearly — examiners penalise mixing up FSH, LH, oestrogen, and progesterone roles.

Exam Traps

  • Do not say LH triggers egg development — that is FSH; LH triggers ovulation.
  • Avoid claiming testosterone regulates the menstrual cycle in females.

Sexually transmitted infections (STIs)

Definition
Infections transmitted through sexual contact via bodily fluids.
HIV/AIDS
HIV is a pathogen that attacks lymphocytes, reducing the body’s ability to produce antibodies. This leads to AIDS, making the host vulnerable to fatal infections.
Control
Abstinence, using protection (condoms), and avoiding risky practices.

Exam Traps

  • Do not say HIV is a bacterium or that antibiotics cure viral STIs such as HIV.
  • Avoid confusing HIV (virus attacking lymphocytes) with a bacterial STI treated by antibiotics.

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