The uterus is about 7.5 cm in length in the nonpregnant woman, and consists of a main portion (body) with an elongated lower part (neck), at the extremity of which is the opening (os). The upper rounded portion of the uterus, opposite the os, is the fundus, at each extremity of which is the horn marking the part where the uterine tube joins the uterus and through which the ovum reaches the uterine cavity after leaving the ovary. The organ is supported in the pelvic cavity by the broad ligaments, round ligaments, cardinal ligaments, and rectouterine (relating to rectum and uterus) and vesicouterine (relating to bladder and uterus) folds or ligaments.