Anatomy and physiology

The cervix is the narrow neck of the uterus and is located between the vagina and the uterus. It projects into the vagina and the cavity of the cervix is known as the cervical canal. The cervical canal's glands secrete a mucus that blocks the entry of sperm except in the midcycle when a reduction in viscosity allows sperm to pass (Marieb and Hoehn [96]) (Figure 20.3).
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Figure 20.3  The cervix. Source: Dougherty and Lister ([38]).