The prostate is an exocrine gland of the male mammalian reproductive system. Its main function is to secrete and store a clear, slightly basic fluid that constitutes up to one-third of the volume of semen. The prostate differs considerably between species anatomically, chemically, and physiologically. A healthy human prostate is slightly larger than a walnut. It surrounds the urethra just below the urinary bladder. It is located in front of the rectum and can be felt during a rectal exam.
The male urethra has two functions: to carry urine from the bladder during urination and to carry semen during ejaculation. Within the prostate, the urethra coming from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts. Semen is composed of sperm and seminal fluid; about 10-30% of the seminal fluid is produced by the prostate gland, the rest is produced by the two seminal vesicles. The prostate also contains some smooth muscle that helps to expel semen during ejaculation.
Prostatic secretions vary between species. They are generally composed of simple sugars, and are often slightly basic. In human prostatic secretions, the protein content is less than 1% and includes proteolytic enzymes, acid phosphatase, and prostate-specific antigen. Its secretions also contain zinc and citric acid.
"Pegging" describes a sexual practice by which a man is anally penetrated by a woman’s use of a strap-on type harness with a g-spot style dildo or the "strapless" dildo, which also provide intense prostate stimulation for some men, especially feeling the "connection" with their partner. Bend over boyfriend, you’re gonna like this! Electroejaculation is a procedure in which nerves are stimulated via an electric probe, which is inserted into the rectum adjacent to the prostate.
Prostate milking (also seen as "prostatic milking") is more commonly encountered as part of BDSM activities, such as games involving the erotic use of sexual denial. It only applies to a male, females not having this type of sexual anatomy.
The release felt by a man as a result of prostatic milking against a background of denial, is described as long, drawn out, but not reaching a resolution phase as with normal orgasm. It is therefore said to always leave an edge of not having had full satisfaction, or a yearning for more, as opposed to the "drop" in responsiveness due to satiation after a full orgasm. For people who engage in lifestyle chastity and erotic sexual denial, this may be desirable, since after orgasm a male is sated and released for some days of the tension which builds up with orgasm denial.
The technique of prostate massage actually involves the prostate gland, the seminal vesicles, and the ampulla, which is the reservoir which actually holds the male sperm just prior to ejaculation. The prostate gland when engorged can be felt by pressing a finger into the middle of the perineum (in back of the scrotum). It is a rounded lump about the size of a large marble. It can also be accessed via the rectum, where it can again be felt as a rounded lump toward the front of the body and just about an index finger’s length inside the rectum. A better way to find it from the rectum is to insert the middle finger, and slide it from just inside the rectum (on the front side) up and in until you feel it move over a lump. That will be the prostate. Just in back of (up from) the prostate is a smaller and roughly triangular wedge shaped nodule that is the bottom portion of the somewhat larger seminal vesicles, which is where most of the fluid of the ejaculate is produced and accumulated. Underneath the seminal vesicles are the ampulla.
During sexual arousal, sperm and ejaculatory fluid accumulate in these glands backing up behind valves in the ejaculatory ducts. When fluid pressure reaches a high enough threshold, the valves open and the urethral bulb fills, triggering the ejaculatory reflex and muscular contractions of orgasm, which empties the glands.
The seminal vesicles, ampulla and prostate can also be emptied by massage of these glands through the rectum. Rhythmically massaging the organs in an in-and-out motion with an anal device or use either the middle finger or the middle finger and index finger together (well lubricated), to apply a firm slow massage over the nodules of the glands inside the rectum. The massage will force the seminal fluid and sperm past the valves in the ejaculatory ducts, and empty the prostate (which discharges directly into the urethra). If arousal is low or penile stimulation is stopped for a brief time before the prostate massage begins, draining of the ejaculate into the urethra will not trigger orgasm. Once ejaculate appears at the meatus, it will help to empty the urethra by running a finger firmly up the underside of the penis from the root to the head, pushing the ejaculate in front of it.
As a side note, part of the mechanism for orgasm for a male involves the accumulation of fluids within the prostate and associated ducts; accordingly once milked, a male will be incapable of achieving orgasm regardless of the degree of stimulation, for some time after.