What is The Female Orgasm?

Orgasm. The male and female orgasms are very similar subjectively. When women and men are asked to described the sensations they feel during arousal and orgasm but excluding gender-specific anatomical terms, the descriptions are remarkably similar, and involve feelings of inevitability when the orgasm is imminent. Of course there are anatomical differences and women have the general advantage that most can have (or be educated to have) multiple orgasms. Also, a good proportion of women can experience a very prolonged orgasm called a 'status orgasmus' which, as far as I know, no man can. These can last many seconds and must be fun :-). Also, many women are capable of imagining themselves all the way to orgasm though no doubt this may involve a lot of muscle tensing and cannot really be described as being without physical stimulus ­ rather no fingers are involved. Women also tend to have more orgasms in their sleep than men who usually only do this during teenage years, and several, mainly anti-depressant, drugs (e.g. Prozac, Zoloft, Wellbutrin) are known to cause spontaneous orgasms in women though they do not affect men the same way - in these cases the orgasm can even sometimes be brought on voluntarily by yawning!

Pain thresholds increase during arousal (e.g. during masturbation) and reach their maximum during orgasm. It is likely that cerebral endorphins may be involved. Electroencephalography has shown which regions of the brain and brain stem are involved in orgasm, though most of the mechanisms of the physiological rather than psychological processes are in the spinal cord and paraplegics can be stimulated to have orgasm.

The standard textbook description of female excitation and orgasm goes like this: A prolonged period of arousal, a plateau, orgasm proper and resolution. The same phases can be identified in men. Major studies which are still often quoted are those of Kimsey and of Masters and Johnson who tackled the sensitive topic of female sexuality in what was effectively the dark ages of the post-war 20th century.

Arousal
In the excitement phase, often induced by thought alone, involves the following set of processes:

The nipples typically become erect and the clitoris also becomes turgid and it expands a little (though not much), and this may result in it becoming a bit more visible in some women with medium to large ones. Clitoral erection, more properly called tumescence, is due to increased arterial blood flow to the clitoris and reduced venous drainage and so is essentially identical to the process of penile erection but the degree of expansion is much less and involves little change in length, though the change in thickness and turgidity of the long clitoral shaft is very easily appreciated. Increasing heart rate and blood pressure, and increasing genital blood flow also result in gradual expansion of the inner and outer labia and vaginal lubrication. Vaginal lubrication results mostly from a process called transudation ­ that is, the increased blood flow (vasocongestion) of the vaginal wall causes blood and lymphatic fluids to be forced through the tissue into the vagina where it appears as a lot of tiny sweat-like drops on the vaginal walls. Additional vaginal lubrication comes from the cervix which is well-supplied with mucous glands. The amount and thickness of a woman's vaginal lubrication may well depend on her stage in the menstrual cycle primarily because of the changes in the cervical mucus.

There is also lubrication of the inner lips resulting from glandular secretions from the mucous membranes and possibly from the Skene's glands (paraurethral glands) that open at two small, sometimes quite visible, pores, one on either side of the urethral opening (at 5 and 7 o'clock if the genitals are arranged with clitoris at 12 o'clock).

As the arousal continues, the swelling of the labia causes the inner lips to part and spread outwards ­ thus making the opening of the vagina more obvious. The increased blood flow causes the woman's genitals to change colour, from flesh tones to at least pinkish, but in women who have had children (it isn't clear if pregnancy alone causes this or childbirth is important) the colour change can be more extreme and her genitals can become almost a deep wine red.

The colour of the vaginal walls also changes in the same way, and internally the vaginal cavity expands and the inner two thirds can form a rather large space; evolutionarily this is probably to produce a cavity in which sperm will be kept in close proximity to the cervix and not simply run out after the male has shed his load. On the other hand, the outer third of the vagina (the introitus) becomes tighter due to the increased blood flow to the region (reported as a corpus spongiosum ­ i.e. similar tissue to that in the penis and clitoris). Internally the positions of the uterus moves causing the vagina to elongate, and the position of the cervix changes ­ collectively these changes in the internal vaginal arrangement are often referred to as "tenting".

Late in the excitement phase the breasts are reported to swell, though it is hard to find detailed measurements.

Plateau
The plateau is the final phase of excitement when basically all excitement parameters are at max and she is waiting to get herself over the edge, usually focusing her thoughts very much on her genitals or other arousing things. At this time spontaneous contractions of the anal sphincter, and muscles in the upper legs and pelvic region are common, and increased semi-involuntary movements of the hips usually indicates the imminence of orgasm.

Orgasm
The orgasm is a pulsatile event with strong feelings of pleasure centred around the genitala and a demanding pushing feeling. In women this is usually indicated visibly by a series of contractions in the vaginal-anal area which occur at about once every 0.8 seconds approx. and by a "sex flush" which is a rapid change in skin colour of the chest (breasts and area between them up to the neck and face) resulting from an increase in cutaneous blood flow. The rate of perineal contractions may vary from woman to woman, and certainly not all contractions in an orgasmic series are evenly spaced, the first usually being relatively long. Internally, a lot more is going on, and videos of the inside of the vagina during orgasm show the cervix is very active and with each contraction it pushes down and "drinks" up semen from the puddle that would be there after a normal copulation ­ so evolutionarily it only makes sense for the woman to come after the man has and only to do so if she wants to get pregnant by him! There are also waves of contractions of the uterus which are stimulated by the orgasmic surge in the hormone oxytosin. During orgasm the woman's blood pressure and heart rate increase considerably and she often does staccato breathing and may vocalise though this may be both voluntary and involuntary depending on the individual. Some hold their breath. Many also show spastic contractions of muscles in the hands and feet causing curling of toes (carpopedal spasms).

Much of the literature about female orgasm reports that during orgasm the clitoris retracts under the clitoral hood. This obviously comes from the studies of Kinsey and others. However, none of the hundreds of videos of real orgasm shown here is this visible. Also, given that the clitoris is composed of spongiform tissue without skeletal muscle, it is hard to see how this could be achieved mechanically as it certainly does not detumesce during orgasm.

The Bartholin's glands (greater vestibular glands) which open just outside the vaginal opening produce a small amount of mucus (just a few drops) and this seems to be secreted just before orgasm. It may be involved in making the chemistry of the vagina less hostile to sperm.

Resolution
After orgasm many women cannot bear continued direct stimulation of the clitoris and/or vulva (and even the breasts in some) and so pass into a resolution phase, but if the stimulation is maintained at a low level until the sensitivity subsides, avoiding direct clitoral contact, quite a lot of women can have a second or even numerous extra orgasms after the first one, separated by a minute or so. After a few orgasms it seems that clitoral sensitivity subsides and continued stimulation is possible. Possibly multi-orgasmicity is not universal in women, though it is likely that the painful, postorgasmic sensitivity of the clitoris puts many off trying. In men it is possible but is exceedingly rare.

In early resolution there may be one or more infrequent contractions of the perineal muscles and anal sphincter that feel pleasurable (often referred top as aftershocks), but basically this is a time when the swelling of the breast and genitals slowly subsides over a period of many minutes (often about 20 mins). Failure to reach orgasm after reaching plateau can be very uncomfortable for some women because there has been no trigger to start the vascular decongestion of the genitals.

Female Ejaculation
Female ejaculation is still a much debated phenomenon. There is no doubt that many women produce, and may forcibly expel in squirts, small to copious amounts of a clear fluid from their urethral opening during high levels of excitement or orgasm. Sometimes this seems very similar to urine but typically is less yellow and there are several scientific papers that claim it contains enzymes not found in urine but present in male semen (phosphatases formed in men in the prostate gland that is responsible for the bulk of male semen volume). Surprisingly there is considerable lack of agreement about whether these secretions can come from supposed peri-urethral reservoirs. Most likely there is a mixture of urine (especially in women who produce 10s of mls of ejaculate, and some urethral products.

Viagra and other similar drugs that activate the nitrous oxide neurotransmission system which seems to be particularly associated with the genital area, can have very similar effects in men and women. In men they can produce (with appropriate mental stimulus usually) erection. In women they cause (often spectacular) genital swelling and lubrication.

The "orgasm nerve" is only known in women and was discovered accidentally during a conscious spinal operation. Stimulating it causes an instant orgasm. No such nerve has been found in men, though interestingly, paraplegic men can have orgasms and ejaculate either by extreme penile stimulation or intense electrostimulation of the prostate region (via the rectum) though in this case the subject has to be under general anaesthetic as the stimulation levels would otherwise be agonising.