October 7, 2010

Birds and Bees Part II

Let me tell you ‘bout the “Birds and the Bees”
And the flowers and the trees
And the moon above
And a thing called “Love”  (Herb Newman)

Following ejaculation, sperm are deposited as a coagulum of secretions from not only the testicles, where sperm are made, but also from the seminal vesicles, prostate, and other accessory glands within the male reproductive tract. In the vagina this coagulum takes some minutes to liquefy so that sperm can begin their arduous journey through the female reproductive tract in search of the elusive egg. While some sperm may swim quite fast, appearing in the upper female reproductive tract (fallopian tubes also called oviducts) within minutes, the majority of ejaculated sperm are destined to die an inglorious death within the acidic secretions of the vagina. Although, at the time of ovulation (when the egg is released from her confines within the ovary), cervical secretions increase in an attempt to neutralize the otherwise caustic (to sperm) environment. Some sperm (the lucky ones) enter this rather neutral cervical mucus and hide in the cervical crevices where they may be safely stored and remain alive for two or three days. It is here in the sanctuary of the cervical crypts that sperm acquire their ability to fertilize in a process called capacitation. During this respite, sperm are released over time and aggressively swim up into the uterus, through the tubal openings called ostia and, into the fallopian tubes. This is why it is not necessary to have intercourse every day (at least to get pregnant), even though the egg is only able to be fertilized for about 24 hours. At least 11 million moving sperm are needed in the vagina to achieve a pregnancy even though only one victorious sperm is normally allowed the privilege of fertilizing the egg that was made receptive by the hormonal machinations leading up to and including ovulation.

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Joseph A. Hill, III, M.D.

Joseph A. Hill, III, M.D. Board-Certified in Reproductive Endocrinology and Infertility