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 Cervix:

 The cervix is the lower most part of the uterus and is made up of strong muscles. It also provides support to the uterus due to attachment of muscles from the pelvic bone. The cervix protrudes and opens through a canal into the vagina.

The function of the cervix is to allow flow of menstrual blood from the uterus into the vagina, and direct the sperms into the uterus during intercourse.

The opening of the cervical canal is normally very narrow. However under the influence of the body hormones and the pressure from the fetal head, this opening widens to about 4 inches (10 cm.) during labor, to allow the birth of a baby.

Read more: Cervix - Anatomy & Function | Medindia http://www.medindia.net/patients/patientinfo/cervix-function.htm#ixzz2ePe7kTnC