<Tr> <Th> FMA </Th> <Td> 17740 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The cervix or cervix uteri (Latin: neck of the uterus) is the lower part of the uterus in the human female reproductive system . The cervix is usually 2 to 3 cm long (~ 1 inch) and roughly cylindrical in shape, which changes during pregnancy . The narrow, central cervical canal runs along its entire length, connecting the uterine cavity and the lumen of the vagina . The opening into the uterus is called the internal os, and the opening into the vagina is called the external os . The lower part of the cervix, known as the vaginal portion of the cervix (or ectocervix), bulges into the top of the vagina . The cervix has been documented anatomically since at least the time of Hippocrates, over 2,000 years ago . </P> <P> The cervical canal is a passage through which sperm must travel to fertilize an egg cell after sexual intercourse . Several methods of contraception, including cervical caps and cervical diaphragms aim to block or prevent the passage of sperm through the cervical canal . Cervical mucus is used in several methods of fertility awareness, such as the Creighton model and Billings method, due to its changes in consistency throughout the menstrual period . During vaginal childbirth, the cervix must flatten and dilate to allow the fetus to progress along the birth canal . Midwives and doctors use the extent of the dilation of the cervix to assist decision - making during childbirth . </P>

The opening of the uterus is referred to as