Question

How does sperm reach ovum?

Answer 1

Sexual reproduction is the formation of a new individual following the union of two gametes.
For fertilization to occur, sperm must be deposited in the vagina within a few (5) days before or on the day of ovulation. Sperm transfer is accomplished by copulation. Sexual excitation dilates the arterioles supplying blood to the penis. Blood accumulates in three cylindrical spongy sinuses that run lengthwise through the penis. The resulting pressure causes the penis to enlarge and erect and thus able to penetrate the vagina. Movement of the penis back and forth within the vagina causes sexual tension to increase to the point of ejaculation.
Once deposited within the vagina, the sperm proceed on their journey into and through the uterus and on up into the fallopian tubes. It is here that fertilization may occur if an "egg" is present. Sperms swim towards the egg by chemotaxis following a gradient of progesterone secreted by cells surrounding the egg.
Fertilization begins with the binding of a sperm head to the glycoprotein coating of the egg (called the zona pellucida). Exocytosis of the acrosome at the tip of the sperm head releases enzymes that digest a path through the zona and enable the sperm head to bind to the plasma membrane of the egg.