Describe the structure and functions of the placenta.

The placenta is formed from the chorionic villi of the embryo interlocking with the uterine tissue of the mother. It allows oxygen and nutrients to pass to the foetus and carbon dioxide and nitrogenous wastes to pass back, it secretes hormones including human chorionic gonadotrophin, oestrogen and progesterone that maintain the pregnancy, and it acts as a barrier to many harmful substances and pathogens.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

Maternal and foetal blood never mix.