The clitoris is made of spongy tissue which can up fill with blood. This engorgement of tissue is vaso-congestion. Upon sexual arousal, extra blood from the pelvic arteries is pumped into the tissue, filling up the spongy spaces so that the clitoris swells in size. The muscles on each side contract and squeeze the only vein which runs along the top of the clitoris. This traps the extra blood inside; it cannot drain out. As more blood is pumped in, the swollen clitoris stiffens, rises, and lengthens to its maximum size. This is the process by which both the clitoris and penis become erect.
At the same time, extra blood is pumped into the vulva area, which thickens and flushes a deep red or purple. The outer labia swell to two or three times their pre-arousal size. The vagina responds with the sweating phenomenon. The walls are coated with moisture. The extensive system of connecting veins and muscles throughout the pelvis all respond to vaso-congestion. There is a feeling of fullness and heaviness, known as pelvic congestion. All this assists to move the woman towards the "orgasmic platform".
The nipples also contain erectile tissue. At an early stage in arousal, they begin to harden and erect. The areola swells and spreads. The entire breasts are affected; they plump up and feel more tender; they are erotically charged when touched.
The Big O!
The clitoris and nipples are the main organs of arousal. If one or both are erotically stimulated for long enough, excitement increases until sexual tension becomes almost overpowering. As orgasm draws near, the clitoris becomes exquisitely sensitive; it cannot tolerate any more direct stimulation. It retracts, pulling back and retiring beneath its hood. Less often, the nipples become equally sensitive, and require no further stimulation.
Sexual tension is built by rhythmic friction. The thrusting of the penis causes maximum friction, maximum sensation, on the outer third of the vagina walls. In the missionary position, man on top, thrusting puts rhythmic pressure on the labia, which allows stimulation of the clitoris, though to a milder degree. Sucking or stroking the nipples in rhythmic movement produces the same effect. Erotic friction can be gentle or tough, slow or rapid, depending upon the particular needs at the time. Whichever, it must be rhythmic and persistent to build maximum sexual tension. As excitement increases, the entire body is charged with waves of tense pleasure. Muscle contractions ripple throughout the system. Like a waiting sneeze which has been building up, the persistency of the "friction factor" finally becomes explosive. The orgasmic platform has arrived. Now is the point of no return.
The vagina and surrounding tissues, the uterus, and sometimes the anus muscles all contract to a rhythmic beat at 0.8 second intervals; the same beat as in male orgasm. This beat can occur from between 3 to a maximum of 15 times, the same beat as in men. The last contractions are little more than ripples or shudders, again as in men. The more intense the orgasm, the longer the contractions last. A few women (and men) can have orgasms with no erotic friction whatsoever. They do it by fantasy, by imagination alone. Other women can have orgasms simply when they are kissed; the neck, earlobes, palms of the hands, toes -- any part can be an erogenous zone.
The big "O' varies. It is not always so big. There can be physical and emotional pleasure of such exquisite intensity that the feelings seem unendurable. There can be pleasing but low-key sensations which feel on a par with the satisfaction of a long-awaited sneeze. The degree of sensation at orgasm does not necessarily reflect on the woman, her partner, or the situation. They reflect on life. Orgasm is as variable as life itself.