Sexual arousal results in a number of physical changes in the vulva. Arousal may be broken up into four somewhat arbitrary phases: Excitement, Plateau, Orgasm, and Resolution.

Excitement

Vaginal lubrication begins first. This is caused by vasocongestion of the vaginal walls. Increased blood pooling there causes moisture to seep from the walls. These droplets collect together and flow out of the vagina, moistening the vulva. The labia majora flatten and spread apart, and the clitoris and labia minoraincrease in size.

Unlike in men, where sexual excitement causes readily apparent erections, women experiencing arousal are not necessarily aware that their vaginas have become lubricated and engorged with blood.

Plateau

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, approximately 2–6 times, causing them to spread apart, displaying the vaginal opening. 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.

Orgasm

Immediately prior to the female orgasm, the clitoris becomes exceptionally engorged, causing the glans to appear to retract into the clitoral hood. This is thought to protect the sensitive glans during orgasm. However, there is some doubt that this is the case, since the same engorgement prior to orgasm occurs in the male homologous structure, the penis, the function of which is thought to be to extend the penis as close to the cervix as possible prior to ejaculation.

Rhythmic muscle contractions occur in the outer third of the vagina, as well as the uterus and anus. They occur initially at a rate of about one every 0.8 seconds, becoming less intense and more randomly spaced as the orgasm continues. An orgasm may have as few as one or as many as 15 or more contractions, depending on its intensity. Orgasm may be accompanied by female ejaculation, causing liquid from either the Skene's gland or bladder to be expelled through the urethra.

Immediately after orgasm the clitoris may be so sensitive that any stimulation is either exciting or uncomfortable.

Resolution

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.