IGCSE Biology glossary
Placenta
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
An organ that develops in the uterus during pregnancy, providing the interface between the mother's blood and the fetus's blood. Nutrients and oxygen diffuse from the mother's blood to the fetus, while carbon dioxide and urea diffuse from the fetus to the mother. The two blood supplies do not mix.
What to include in an exam answer
The mother's blood and fetus's blood do NOT mix. Substances cross the placenta by diffusion (oxygen, CO2, glucose) and active transport (some nutrients). The placenta also acts as a barrier to some pathogens (but not all, e.g. Rubella can cross).
Example in context
Explain two functions of the placenta (2 marks): The placenta allows oxygen and nutrients to pass from the mother's blood to the fetus's blood by diffusion, providing for growth and respiration. It also allows waste products like carbon dioxide and urea to pass from the fetus to the mother for removal.
Related syllabus topic
Reproduction