The opening of the vagina is located at the bottom of the vulval vestibule, toward the perineum. The term introitus is more technically correct than "opening", since the vagina is usually collapsed, with the opening closed, unless something is inserted. The introitus is sometimes partly covered by a membrane called thehymen. The hymen will rupture during the first episode of vigorous sex, and the blood produced by this rupture has been seen as a sign ofvirginity. However, the hymen may also rupture spontaneously during exercise (includinghorseback riding) or be stretched by normal activities such as use oftamponsandmenstrual cups, or be so minor as to be unnoticeable. In some rare cases, the hymen may completely cover the vaginal opening, requiring asurgical incision. Slightly below and to the left and right of the vaginal opening are twoBartholin glandswhich produce a waxy,pheromone-containing substance, the purpose of which is not yet fully known.
The appearance of the vulva and the size of the various parts vary a great deal from one female to another, and it is also common for the left and right sides to differ in appearance. Fluids and odor
There are a number of different secretions associated with the vulva, includingurine,sweat,menses, skin oils (sebum), Bartholin's andSkene's glandsecretions, and vaginal wall secretions. These secretions contain a mix of chemicals, includingpyridine,squalene,urea,acetic acid,lactic acid, complexalcohols,glycols,ketones, andaldehydes. During sexual arousal,vaginal lubricationincreases.