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Unformatted text preview: The vagina (birth canal) serves both as the passageway for a newborn infant and as a depository for semen during sexual intercourse. The upper region of the vagina surrounds the protruding cervix, creating a recess called the fornix. The lower region of the vagina opens to the outside at the vaginal orifice. A thin membrane called the hymen may cover the orifice. The vaginal wall consists of the following layers: The outer adventitia holds the vagina in position. The middle muscularis consists of two layers of smooth muscle that permit expansion of the vagina during childbirth and when the penis is inserted. The inner mucosa has no glands. But bacterial action on glycogen stored in these cells produces an acid solution that lubricates the vagina and protects it against microbial infection. The acidic environment is also inhospitable to sperm. The mucosa microbial infection....
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- Spring '10