(a) Explain the role of placenta in the development of human embryo.
(b) Give example of two bacterial and two viral sexually transmitted diseases. Name the most effective contraceptive which prevents spread of such diseases.
(a) Role of placenta in the development of human embryo:
A special tissue develops between the uterine wall and the embryo (foetus) called placenta, where exchange of nutrients, glucose and oxygen takes place. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta. The development of the child inside the mother’s blood takes approximately nine months.
(b) Sexually transmitted diseases (STDs) transmitted by bacteria are:
(i) Gonorrhoea
(ii) Syphilis STDs transmitted by virus:
(i) AIDS
(ii) Genital warts
The most effective contraceptive which prevents the spread of these diseases is by the use of mechanical barriers such as physical devices like condoms.