CBSE Class 10 Science 2017 · Paper 31/1/1 · Question 20

(a) The testes (singular testis) produce sperms and also secrete a hormone. The hormone is testosterone. Its functions: it regulates the formation of sperms, and it brings about the changes in appearance seen in boys at puberty (such as the growth of facial and body hair and the deepening of the voice). (b) Fertilisation occurs in the oviducts (fallopian tubes): the egg released by an ovary passes into an oviduct, the sperms travel up through the uterus into the oviduct, and they meet there. (c) After fertilisation the zygote is implanted in the thick, blood-rich lining of the uterus and develops into an embryo. It gets nutrition from the mother's blood through a special tissue, the placenta, a disc embedded in the uterine wall and joined to the embryo by the umbilical cord. The placenta has villi on the embryo's side, and on the mother's side there are blood spaces surrounding the villi. The villi provide a large surface area, so glucose and oxygen pass from the mother's blood to the embryo, and the wastes produced by the embryo pass into the mother's blood to be removed.