i) Explain the terms:

a. implantation


b. placenta


ii) What is the average duration of human pregnancy?

i) a. Implantation: The fertilised egg (zygote) starts dividing and form a ball of cells or embryo. The embryo is implanted in the lining of the uterus where they continue to grow and develop organs to become foetus. Hence the uterus prepares itself every month to receive and nurture the growing embryo. The lining thickens and is richly supplied with blood to nourish the growing embryo. This whole process is called implantation.


b) Placenta: The embryo or child in the womb gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta.


ii) The sexual act always has the potential to lead to pregnancy. The average duration of human pregnancy is approximately about nine months.


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