Acrosome reaction
The process

The acrosomal reaction typically occurs in the ampulla of the fallopian tube, the site of fertilization, when the sperm penetrates the secondary oocyte. Prior events prepare for the acrosome reaction. The sperm cell undergoes a series of changes, including acquiring a "hyperactive motility pattern" where its flagellum produces vigorous whip-like movements propelling the sperm through the cervical canal and uterine cavity until it reaches the isthmus of the fallopian tube. Various mechanisms, including chemotaxis, aid the sperm in approaching the ovum in the ampulla of the fallopian tube. Once in close proximity, glycoproteins on the outer surface of the sperm bind with glycoproteins on the zona pellucida of the ovum.
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