Sex is regarded as the deepest form of physical and emotional connection. The process is a result of a series of hard-wired biological responses within the brain that stimulate the sexual organs of male and female bodies. A deep love and emotional connection is also sometimes present, although that is certainly not a scientific requirement for an erect penis to be able to penetrate a moist vagina. The following is a clinical look at the biological processes that occur while humans engage in what has historically been their favorite recreation. Using a model developed by human sexuality experts decades ago, the entire process can be divided into four phases. It should be understood that the phases have no predetermined length or ending, and are all interwoven together to form the process, making them simply one large step from another perceptual vantage point.
Excitement Phase (Arousal)
The initial phase of sexual intercourse involves a male and female becoming aroused. This happens very quickly after the initial stimulation. For a male, blood will begin to pump into his penis and it will become anywhere from slightly to moderately erect. The heart rate will increase, and the scrotum will become firmer. In a female, the vaginal area will begin to moisten and transform in length and shape, anatomically and biologically preparing itself to be penetrated. The vaginal opening will tighten slightly, as blood rushes to the inner and outer lips. Engaging in foreplay can serve as a means of allowing time for blood to rush to the proper areas, and natural lubricants to form that can aid in the physical act of intercourse.
During the second phase, breathing and heart rate increases further, and muscles tighten in the legs, thighs, hips, buttocks and hands. In a male, the rush of blood to the penis makes it stiff and fully erect, and the tightening of the veins prevent blood from flowing back out of the penis, keeping it erect. The testes goes up into the scrotum and becomes firmer. During this phase, the female’s nipples becomes erect, firm and the vaginal lips becomes slightly puffy. Glands continue to produce lubrication that cause vagina to become wet and ready for penetration.
Orgasmic Phase (Intercourse)
When the male inserts his erect penis into woman�s vagina, the climax of intercourse begins. This process can take anywhere from a handful of seconds to few minutes based on a variety of factors, including the strength of certain penis muscles. During sex, the male slides his penis in and out of the vagina using a thrusting motion, which pleasures the nerves concentrated near the bottom of the head of the penis until it reaches orgasm. When male reaches the point of orgasm, the semen collects in the urethral bulb before being ejaculated out of the tip of the penis by a series of involuntary spasms. The female body also undergoes a number of physical changes during sex. Breasts swell slightly, the areola and labia becomes larger, and the clitoris withdraws slightly. The diameter of the opening of the vagina continues to narrow, creating what sexual behavior experts refer to as an ‘orgasmic platform,’ or, the natural anatomical preparation for a female orgasm. It is possible for a male and female to hit climax simultaneously, or for them to occur separately. For a female, the opening of the vagina and the first few inches of its canal will twitch spasmodically with pleasure, about once every second and for an average of about ten seconds.
After both parties have achieved orgasm, the penis begins to return to its flaccid state, and the puffiness and swelling of the vaginal area subsides. In male, the penis will slowly go from erect to flaccid, usually over the course of two or three minutes. A few drops of semen that remained in the urethral canal may slide out of the flaccid penis in the following minutes. In female, swelling of the vaginal entry and canal will subside. In short time, both the male and female�s blood pressure and heart rates will return to normal.