a stretchable passage from the external sex organs to the cervix and uterus. It is a tube with walls that are made of wrinkled tissue that lay against each other. The walls open just enough to allow something to go into the vagina—a tampon, finger or penis. The vagina is 2-4 inches long when a woman is not aroused and 4-8 inches long when she is sexually aroused. The vagina allows menstrual flow (blood) to leave the body, allows for sexual penetration, and allows the fetus to pass through during a vaginal delivery.