16.4Reproduction

Sexual reproduction in humans — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 9 parts Lesson 7 of 11 1 quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision

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Lesson summary

16.4 Sexual reproduction in humans — IGCSE BIOLOGY notes: Describe the human reproductive systems, gametes and fertilisation, and pregnancy including the placenta.StructureFunctionTestisProduces sperm and testosteroneScrotumHolds the testes outside the body so sperm are slightly …

Sperm flagellum
Sperm acrosome
Sperm mitochondria
Egg cytoplasm
Egg jelly coat
Amniotic sac

Part 1 of 7Male reproductive system

Structure	Function
Testis	Produces sperm and testosterone
Scrotum	Holds the testes outside the body so sperm are slightly cooler than body temperature
Sperm duct	Carries sperm to the urethra
Prostate gland	Produces fluid that mixes with sperm to form semen
Urethra	Carries urine or semen; a ring of muscle prevents mixing
Penis	Passes urine out and places semen in the vagina

Part 2 of 7Female reproductive system

Structure	Function
Ovary	Contains ova which mature when hormones are released
Oviduct	Carries the ovum to the uterus; ciliated; fertilisation occurs here
Uterus	Muscular bag with a soft lining where the zygote implants
Cervix	Ring of muscle at the lower end of the uterus holding the foetus in place
Vagina	Muscular tube that receives the penis and sperm

Part 3 of 7Gametes and fertilisation

Fertilisation

Fertilisation the fusion of the nuclei of a sperm and an egg cell, usually in the oviduct.

Sperm flagellum

Sperm flagellum a tail that lets the sperm swim to the egg.

Sperm acrosome

Sperm acrosome enzymes in the head digest a route into the egg.

Sperm mitochondria

Sperm mitochondria supply energy for movement of the flagellum.

Egg cytoplasm

Egg cytoplasm an energy store for cell division after fertilisation.

Egg jelly coat

Egg jelly coat changes after fertilisation to stop more sperm entering.

Part 4 of 7Sperm and egg compared

Feature	Sperm	Egg
Size	Very small (about 45 µm)	Large (about 0.15 mm)
Structure	Head, flagellum, many adaptations	Round, covered in a jelly coating
Movement	Capable of locomotion	Not capable of locomotion
Numbers	Around 100 million made each day	Thousands of immature eggs but one released each month

Part 5 of 7Development in pregnancy

The zygote travels along the oviduct, dividing repeatedly to form a ball of cells, the embryo.

The embryo embeds in the thick uterus lining (implantation).

Over the first 12 weeks the organs develop, with nutrients reaching the embryo by diffusion.

After this the placenta has formed and the embryo is called a foetus.

The rest of the 9 months is growth in size.

1Amniotic sac

Amniotic sac contains amniotic fluid, made from the mother's blood plasma, which cushions the foetus.

2Umbilical cord

Umbilical cord joins the foetal blood supply to the placenta.

Part 6 of 7The placenta

Exchange

Exchange glucose, amino acids, fats, water and oxygen pass from mother to foetus.

Waste

Waste carbon dioxide and urea pass from foetus to mother.

Diffusion

Diffusion all movement is by diffusion down concentration gradients.

Adaptations

Adaptations a large surface area and a thin wall.

Blood

Blood maternal and foetal blood flow close together but never mix.

Barrier

Barrier it blocks many toxins and pathogens, but some, such as nicotine and the rubella virus, cross.

Part 7 of 7More from the specification

Human Male Reproductive Anatomy

Testes suspended within the scrotum produce flagellated spermatozoa and testosterone,
which travel along the vas deferens and mix with alkaline seminal fluid before ejaculation.

Human Female Reproductive Anatomy

Paired ovaries release secondary oocytes into fallopian tubes (oviducts);
- upon fertilisation, the resulting zygote cleaves as it travels to implant into the vascularised endometrium of the uterus.

Role of the Placenta and Umbilical Cord

The placenta acts as an exchange organ where maternal and fetal bloodstreams come into close proximity, enabling diffusion of nutrients, oxygen,
- and antibodies into fetal blood while expelling urea and carbon dioxide.

Oestrogen

The main female sex hormone, made in the ovaries.

Progesterone

A hormone that maintains the uterus lining.

Asexual reproduction

Reproduction from one parent giving genetically identical offspring.

Menstrual cycle

A monthly series of changes in the female reproductive system controlled by hormones.

Genetically identical

Having the same alleles

Pituitary gland

The master gland whose hormones control other glands.

Genetic variation

Differences in alleles within a population.

Pollen

Grains made by plants, each type with a different shape.

Pollination

Transfer of pollen from an anther to a stigma.

Variation

Differences between individuals of the same species.

Germination

The start of growth of a seed.

Key terms

Term	Meaning
Fertilisation	The fusion of the nuclei of a sperm and an egg cell.
Zygote	The fertilised egg cell.
Implantation	Embedding of the embryo in the uterus lining.
Placenta	The organ where substances are exchanged between mother and foetus.
Umbilical cord	Links the foetus to the placenta.
Amniotic fluid	Fluid that cushions the foetus.
Acrosome	The enzyme-containing head region of a sperm.

Avoid these mistakes

Saying the mother's blood flows into the baby — substances diffuse across the placenta and the bloods never mix.

Giving vague answers like waste products or nutrients — name specific substances such as urea and glucose.

Saying fertilisation occurs in the uterus — it usually occurs in the oviduct.

Saying the foetus forms immediately — the embryo becomes a foetus after about 12 weeks.

Last updated: 14 October 2026