The Vagina
In females, orgasm begins with strong, rhythmic contractions of the outer onethird of the vagina, which Masters and Johnson call the orgasmic platform. These contractions, which may number from three to fifteen, first recur within less than a second, then, as they become weaker, at longer intervals.

Uterus and Anal Sphincter
Almost at the same time, the uterus begins to contract. However, the uterine contractions are irregular. They start at the top, working their way down, not unlike the contractions during the first stage of labor. The sphincter muscles of the rectum may also contract a few times at the same intervals as the orgasmic platform.

Muscular Tension, Pulse Rate and Blood Pressure
In general, there is great muscular tension, not only in the entire pelvic area, but also in other parts of the body, such as the neck, arms, hands, legs, and feet. The pulse rate and blood pressure rise slightly even beyond the level reached during the plateau phase, and breathing is very fast. The intensity of all of these physical reactions depends, of course, on the degree and duration of sexual tension.