What is What is the shape of external os in nulliparous female ? and explain in detail?
In a nulliparous woman, i.e. a woman who has not borne children, the external os is small and circular. However, in multiparous women, the external os is bounded by anterior and posterior lips, both of which are in contact with the posterior wall of the vagina. Ref : B D Chaurasia's Human Anatomy , seventh edition, volume 2, pg.no.421.