Why the Cervix Is More Amazing Than You Realized

Technically, the cervix is the bottom chunk of the uterus, a circular plug-like mass of tissue dividing the uterine space from the vagina. But where most of the uterine wall is made of smooth muscle, up to 90% of the cervix is built of stiff and unyielding connective tissue. At least, it's stiff most of the time.