The diagram given below is that of a developing human foetus. Study the diagram and then answer the questions that follow: The diagram given below is that of a developing human foetus. Study the diagram and then answer the questions that follow:
Mention any two functions of the part labelled 2 in the diagram.
Topic: Functions of the placenta
Answer
- It acts as a BARRIER, preventing germs and many harmful substances from entering the foetal blood.
- It SECRETES the hormones OESTROGEN and PROGESTERONE, which maintain the pregnancy.
(Also acceptable: it supplies the foetus with oxygen and nutrition from the mother’s blood, and removes its carbon dioxide and nitrogenous wastes.)
Two functions, one mark. The placenta has several, so choose two that differ in KIND.
THE POINT MOST OFTEN GOT WRONG: the blood of the mother and that of the foetus DO NOT MIX. They flow close together, separated by a thin membrane, and substances cross by diffusion. Writing that the mother’s blood flows into the baby is a definite error.
The placenta is remarkable because it does the work of several organs at once — LUNGS, DIGESTIVE SYSTEM, KIDNEYS and an ENDOCRINE GLAND — since none of the foetus’s own organs is yet functioning.
Note the LIMIT of the barrier function: it stops most germs but not all, and not alcohol, nicotine or many drugs — which is why these harm the foetus.