The Penis
Given the amount of attention to this important body part, it is strange that there is so much myth, mystery and misinformation about the penis. First off, there are no bones or muscles in the penis. In fact, the penis is made up primarily of spongy tissue, which becomes engorged with blood during erection. Two or three inches of the penis are rooted inside the body in the pubococcygeus muscle (PC muscle) and it is possible to strengthen this muscle for stronger erections, stronger orgasms and better ejaculatory control.

The Testicles
Because normal body temperature is too hot for sperm production, testicles hang down, away from the body. As ejaculation nears, the testicles are pulled toward the body. Sperm move through the vas deferens, a firm tube that extendes from the testicles to the prostate gland, where they mix with secretions to form ejaculate. The sperm are actually only a small part of the ejaculate.

The Prostate
The prostate is a gland that lies at the center of the pelvis and is highly sensitive to sexual stimulation. Some authors have even called it the male G-spot. During erotic stumlation, the prostate becomes increasingly aroused. The closer a man is to orgasm, the more sensitive the prostate is. About 1/3 of the ejaculate comes from the prostate, so keeping the prostate healthy is very important (though examinations can be unpleasant). The prostate can be stimulated externally or through the anus.

The Perineum
The perenium is the area between the base of the testicles and the anus. This area can be very sensitive to sexual stimulation, especially during orgasm.

The Pubococcygeus (PC) Muscle
The PC muscle is actually a group of muscles that run from the pubic bone in front to the tailbone in the back. The PC muscle is used every time he stops the flow of urine from his bladder. It is also the muscle that contracts when he ejaculates, moving the semen up through the penis and out of the body.

The Anus
Due partly to it's proximity to the prostate gland and partly to its own high concentration of sensitive nerve endings, the anus is a highly erogenous zone for many men (both gay and straight). Extra care must be taken while sexually exploring this area, as it is rich with bacteria.