Polyspermy means an egg has been fertilized by more than one sperms. The zona pellucida is modified by proteases. The proteases destroy the protein link between the cell membrane and the vitelline membrane, remove any receptors that other sperm have bound to, and help to form the fertilization membrane that prevents polyspermy.

Prolactin hormone controls the synthesis of milk proteins in the mammary glands, Progesterone controls the development of alveoli of mammary glands and the release of milk during lactation is stimulated by the rise in the level of oxytocin.

The placenta secretes hormones like human gonadotropins, human placental lactogen, oestrogen and progesterone that are necessary to maintain pregnancy. Due to the secretion of these hormones, it is called an endocrine gland.

(i) A - Utreus B - Fallopian tube C - Ovary D - Vagina 
(ii) The penis reaches into the vaginal area thus, the sperms are released in vagina.

The high concentrations of LH induce rupture of mature Graafian follicle and causes the release of secondary oocyte thereby causing ovulation in females.

Differences between spermatogenesis and spermiogenesis are

Amoeba, Euglena; blastos.

Activation of sperms within the female tract of mammals is called capacitation, without which fertilization is impossible.

During pregnancy,the corpus luteum secretes large quantity of progesterone,which inhibits maturation of any other follicle or ovulation;hence menstrual cycles are absent.

Gametogenesis \(\rightarrow \) Insemination \(\rightarrow \) Fertilisation \(\rightarrow \) Implantation \(\rightarrow \) Gestation \(\rightarrow \) Parturition .