Physiology, Cervical Dilation

The cervix is a fibromuscular organ linking the uterus to the vagina. The upper two-thirds of the uterus is termed the corpus, or body of the uterus. The lower one-third of the uterus comprises the cervix, with the upper boundary of the cervix being the internal os. The cervix lies anterior to the bowel and posterior to the bladder. Anatomically, internal to external: uterine cavity, internal os, endocervix (endocervical canal), external os, ectocervix, vagina. In pre-menopausal women, the cervix faces downward and protrudes into the vagina. The cervix serves as a passageway between the endometrial cavity and the vagina and is physiologically important in reproduction and childbirth. Towards the end of pregnancy, as the time of labor approaches, the cervix must undergo cervical effacement (thinning) and dilation (widening) to facilitate and accommodate the delivery of the fetus.