In the absence of testosterone, the genital tubercle forms the female phallus, called the clitoris. The clitoris consists of the glans and the internal organ. The clitoral glans is located just above the vaginal opening. Most of the clitoris (the body or shaft) is internal. Just below the mons pubis (that is covered with pubic hair) are the lip-like external structures of the vulva (just below the prominent bone). The labia majora (on the outside) are larger and surround the delicate labia minora (on the inside), which are smaller. They provide protection for the clitoral glans, the urethra and the vaginal opening.
A woman’s sex organ (clitoris) is separate from her internal reproductive anatomy (ovaries, uterus and vagina). The sole function of the clitoris is to be a sex organ. Unlike a man, a woman has separate anatomy for urination (the urethra), reproduction (the vagina) and orgasm (the clitoris). These three functions are all combined for a man and provided by the penis. The female anatomy is more highly evolved (because each part of anatomy has only one function) but a man’s anatomy is more practical and convenient.
The sex organ (penis or clitoris) is the only erectile organ of the body. When a person is aroused (their mind responds positively to eroticism), the brain causes an increase in the rate of blood flowing to the genitals. Our physical arousal, which involves increased blood-flow in the corpus cavernosa causes swelling to varying degrees, called tumescence, of the sex organ (or phallus).
The clitoris is largely an internal organ. Only the tiny glans (or bud) is visible externally. The glans tends to be hidden by the labia majora and pubic hair. The glans is covered by a clitoral hood formed in part by the fusion of the upper part of the two labia minora. The body of the internal clitoral organ has two corpora cavernosa that are smaller but analogous to those of the penis. When aroused these tissues are engorged with blood. After orgasm has been achieved, the excess blood is released back into the circulation.
The clitoris is the homologue of the penis but the two organs develop to a very different extent both before birth and at adolescence. The body of the clitoris consists of two parallel corpora cavernosa of erectile tissue (which may increase to over 2 inches when aroused), smooth muscle and connective tissue (collagen and elastin) surrounded by a fibrous sheath (tunica albuginea). But the clitoris doesn’t have the same mechanism for trapping blood (a muscle within the corpora cavernosa) that the penis has. The clitoris becomes tumescent (swollen) but it does not become erect (rigid) as the penis does. This explains why women are largely unaware of this much lesser physical arousal. When masturbating, a responsive woman needs to use quite extreme (surreal) erotic fantasies to access her subconscious arousal.
It is very evident that men are sensitive to stimulation (capable of reaching orgasm) because of the erection they have due to blood flowing into the penis. Without this arousal, men are incapable of orgasm. The clitoris has equivalent structures (corpora cavernosa). It is inconceivable that these would not have the same function in a woman as for a man. It is equally inconceivable that women have evolved a quite different mechanism (separate from the male) for a response as basic and primitive as orgasm.
However, the clitoris is never rigid and so it lacks the extreme sensitivity of the penis. Since neither the clitoris nor female orgasm are involved in reproduction, women do not experience the acute arousal that men do, from responding to real-world erotic stimuli. A woman may be indifferent to gentle stimulation of the glans (over the hood) but due to hypersensitivity she can also feel discomfort, or even pain, if stimulation is too aggressive. If a woman stimulates her glans without any accompanying mental arousal, there is no pleasure. The clitoris is not an external phallus that can be used to impregnate another person. Consequently, women do not have a sex drive.
Even responsive women do not obtain the same sensational pleasure from clitoral stimulation that men enjoy from penile stimulation. Mental arousal (by focusing on surreal fantasy) and physical arousal (tumescence) provide only mild pleasure. The key pleasures of female masturbation involve the pelvic contractions and the sensation of releasing sexual emotions at the end.
Female orgasm is a miracle for two reasons. Firstly, we usually only evolve functionality for a specific (life-critical) purpose. Secondly, we also lose characteristics that have no useful function. Male orgasm triggers ejaculation but female orgasm has no role in reproduction. Female orgasm is a hangover from how the sexes evolved. As an internal organ, the clitoris has much less significance for a woman than the penis has for a man. The clitoris is the source of female orgasm, which provides a woman’s own personal pleasure.
In younger women there is little externally discernible swelling of the clitoral organ. But in mature women, during periods of subconscious arousal, increased blood-flow can cause the internal clitoral organ to swell. If a woman places her three middle fingers over her vulva, she can feel the top of the pelvic bone. If she then runs her fingers down towards the perineum, she can feel a tingling sensation of the clitoral glans with her index finger. The swollen pubic area is noticeable both to the eye and to touch (by pressing down either side of the labia majora). Clitoral tumescence is not a sign of mental arousal nor does it help with orgasm. The main benefit of clitoral tumescence is an increased sensitivity in the pelvis during intercourse.
The shaft of the clitoris may average something over an inch in length. It has a diameter which is less than that of a pencil. (Alfred Kinsey)
Excerpt from Learn About Sexuality (ISBN 978-0956-894748)