Sexual arousal
Sexual arousal results in a number of physical changes in the vulva. During arousal vaginal lubrication increases. Vulva tissue is highly vascularised; arterioles dilate in response to sexual arousal and the smaller veins will compress after arousal, so that the clitoris and labia minora increase in size. Increased vasocongestion in the vagina causes it to swell, decreasing the size of the vaginal opening by about 30%. The clitoris becomes increasingly erect, and the glans moves towards the pubic bone, becoming concealed by the hood. The labia minora increase considerably in thickness. The labia minora sometimes change considerably in color, going from pink to red in lighter skinned women who have not borne a child, or red to dark red in those that have. Immediately prior to an orgasm, the clitoris becomes exceptionally engorged, causing the glans to appear to retract into the clitoral hood. Rhythmic muscle contractions occur in the outer third of the vagina, as well as the uterus and anus. Contractions become less intense and more randomly spaced as the orgasm continues. The number of contractions that accompany an orgasm vary depending on its intensity. An orgasm may be accompanied by female ejaculation, causing liquid from either the Skene's gland or bladder to be expelled through the urethra. The pooled blood begins to dissipate, although at a much slower rate if an orgasm has not occurred. The vagina and vaginal opening return to their normal relaxed state, and the rest of the vulva returns to its normal size, position and color.