Question:

Fertilization in humans is practically feasible only if

The sperms are transported into cervix within 48 hrs of release of ovum in uterus.

The sperms are transported into vagina just after the release of ovum in fallopian tube

The ovum and sperms are transported simultaneously to ampullary - isthmic junction of the cervix.

The ovum and sperms are transported simultaneously to ampullary - isthmic junction of the fallopian tube

Solution:

The correct option is D. The ovum and sperms are transported simultaneously to ampullary-isthmic junction of the fallopian tube. The motile sperms swim rapidly, pass through the cervix, enter into the uterus and finally reach the junction of the isthmus and ampulla (ampullary-isthmic junction) of the fallopian tube. The ovum released by the ovary is also transported to the ampullary-isthmic junction where fertilization takes place. Fertilization can only occur if the ovum and sperms are transported simultaneously to the ampullary-isthmic junction. This is the reason why not all copulations lead to fertilization and pregnancy.