What is the shape of external os in nulliparous female ?
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.
circular
transvers
veical
oval
Abdomen and pelvis