Excitement in both sexes
Among both sexes, the excitement phase results in an increase in heart rate (tachycardia), an increase in breathing rate, and a rise in blood pressure. An erection of the nipples, especially upon direct stimulation, will occur in nearly all females[citation needed] and approximately 60% of males[citation needed]. Vasocongestion of the skin, commonly referred to as the sex flush, will occur in approximately 50-75%[citation needed] of females and 25% of males[citation needed]. The sex flush tends to occur more often under warmer conditions[citation needed] and may not appear at all under cooler temperatures[citation needed]. It has also been commonly observed that the marked degree of the sex flush can predict the intensity of orgasm to follow[citation needed].
During the female sex flush, pinkish spots develop under the breasts, then spread to the breasts, torso, face, hands, soles of the feet, and possibly over the entire body. Vasocongestion is also responsible for the darkening of the clitoris and the walls of the vagina during sexual arousal. During the male sex flush, the coloration of the skin develops less consistently than in the female, but typically starts with the epigastrium (upper abdomen), spreads across the chest, then continues to the neck, face, forehead, back, and sometimes, shoulders and forearms.
The sex flush typically disappears soon after orgasm occurs, but this may take up to two hours or so, and sometimes, intense sweating will occur simultaneously. The flush usually diminishes in reverse of which it appeared.
An increase in muscle tone (myotonia) of certain muscle groups, occurring voluntarily and involuntarily, begins during this phase among both sexes. Also, the external anal sphincter may contract randomly upon contact (or later during orgasm without contact).
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Excitement in females
In females, venous patterns across the breasts become more visible and the breasts very slightly increase in size, which becomes more observable if lying on the back. The
labia majora become flatter, thinner, and rise upwards and outwards in nulliparous women (those who have not given birth)[
citation needed]. In
parous women (those who have given birth), they may increase two or threefold in size[
citation needed]. The
labia minora may increase in size and may protrude from the labia majora, depending on the size they are in a normal, relaxed state. The
clitoral glans becomes
tumescent, or swollen, like the
glans of the penis. Following stimulation,
vaginal lubrication is produced by the vasocongestion of the vaginal walls. They darken in color and become smoother than normal. Also, the
uterus elevates, more vertically as time passes, and the inner two-thirds of the
vagina expand, usually a total of 7 to 10 cm[
citation needed]
