Reproductive System

Sexual Response and Conception

How many sperm are required to ensure fertilization?

Although millions of sperm may enter the vaginal canal during sexual intercourse, only one sperm enters and fertilizes an ovum. The additional sperm are necessary to increase the chance that one sperm will survive the acidic conditions of the vagina and will successfully complete the journey to the uterine tubes for fertilization. Once the sperm reaches the ovum it releases an enzyme that dissolves the outer wall of the ovum, allowing the sperm to enter. Following fertilization the outer membrane of the ovum thickens to prevent other sperm from entering the now fertilized egg.


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