The lower half is the neck or cervix and is cylindrical; it projects into the anterior wall of the vagina, into the cavity of which it opens by the os uteri externum.
This opening in a uterus which has never been pregnant is a narrow transverse slit, rarely a circular aperture, but in those uteri in which pregnancy has occurred the slit is much wider and its lips are thickened and gaping and often scarred.
The apex leads into the canal of the cervix, but between the two there is a slight constriction known as the os uteri internum.
The uterus may be double, each division opening by a separate os uteri into a common vagina, as in Leporsdae, Sciuridae, and Hydrochoerus, or two-horned, as in most species.
There are two series of ovaries extending through a large part of the body and accompanied by two uteri; the latter open by two oviducts which debouch into an atrium which also receives the intestine and a single receptaculum seminis, and is continued backward as the cloaca; this opens posteriorly.
The two uteri join behind and open to the exterior by a median opening.