Further studies have shown that human spermatozoa can be kept in a noncapacitated state if placed in a suspension saturated with cholesterol. For this biologic process to occur, the spermatozoa plasma membrane and the outer acrosomal membrane must be removed. When hyperactivation was blocked in capacitated, acrosome-reacted hamster sperm bound to the zona, they were unable to penetrate it (stauss. Quantitatively, these findings have been demonstrated following artificial insemination in which the percentage of sperm with normal morphology from the inseminated specimen was known ahead of time, thus allowing a more accurate comparison of the postinseminate semen within the cervical mucus.
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The vagina is open to the exterior and thus to infection, especially at the time of coitus; therefore, it is well equipped with antimicrobial defenses. Sperm movement through the fallopian tube relies on a combination of forces: intrinsic sperm motility, tubular muscular contraction, and fluid flow. 1990, 1991a; smith and yanagimachi, 1991; thomas.