In an experiment, sperms removed from epididymis of a man were added in a dish containing appropriate media and oocyte. No fertilisation was seen. However, when sperms from epididymis were directly placed in uterus of an ovulated woman, she became pregnant. These observations suggest that

Options

A. the sperms need to travel some distance to attain fertilising ability
B. the oocyte secretes some biochemicals or factors which help sperms to fertilise
C. the hormones in the female body help sperms to attain fertilising ability
D. the contents of female reproductivity tract interact with sperms and activate them for fertilisation.

Answer

D

Explanation

Although spermatozoa are said to be "mature" when they leave the epiddymis, their activity is held in check by multiple inhibitory factors secreted by the genital duct epithelia. Therefore, when they are first expelled in the semen, they are unable to perform fertilisation of the ovum. However, on coming in contact with the fluids of the female genital tract, multiple changes occur that activatethe sperm for the final processes of fertilisation. The secretions of the female genital tract remove coating substances deposited on the surface of the sperms particularly those on the acrosome. Thus, the receptor sites on the acrosome are exposed and sperm becomes active to penetrate the egg. This phenomenon of sperm activation in mammals is known as capacitation.