The prostate is a gland located at the base of the bladder of most male mammals. A normal prostate gland is about the size of a walnut that encircles the urethra. It has a variety of purposes including helping expel sperm, transport sperm, extend the lifespan of sperm, and prevent urination during ejaculation.
Prostate glands contribute to the volume and alkalinization of semen. Semen is mainly made up of spermatozoa, or sperm, but about 25 percent of semen is comprised of a milky-white, slightly alkaline solution. This liquid, also known as seminal vesicle fluid, helps to counteract the slightly acidic vagina, thereby helping sperm live longer and have a higher chance of causing a pregnancy.
Fluid produced by the prostate gland — also known as prostatic fluid — varies widely in composition among species. It is usually made up of simple sugars. Human prostatic fluid contains less than 1 percent protein and has high levels of zinc.
In most mammals, the urethra — the tube that carries urine from the bladder out of the body — passes through the prostate gland. This portion of the urethra is known as the prostatic urethra. When the prostate is tightened during ejaculation, the prostate gland itself expands to squeeze the prostatic urethra shut, thereby preventing urination. That muscle contraction also helps expel semen during ejaculation.
The prostate gland is susceptible to several unique health issues, several of which are fairly common. Prostatitis is the inflammation of the prostate gland. It can be caused by a variety of things from bacterial infections to leukocytosis.
Benign prostatic hyperplasia (BPH), or an enlarged prostate, usually occurs in older men where the prostate enlarges sufficiently to interfere with urethral function. In a sense, the prostate expands and squeezes the urethra. This can result in hesitant and/or frequent but incomplete urination. It has been said that most any man that lives long enough will develop BPH. Treatments range from taking alpha-blockers to surgeries — including transurethral resection of the prostate (TURP).
An enlarged prostate is occasionally associated with prostate cancer. This type of cancer is one of the most common cancers suffered by men in developed countries. Fortunately, prostate cancer is often detectable early through regular rectal exams and testing Prostate Specific Antigen (PSA) levels.
Skene's gland, or the paraurethral gland, is the female version of a man's prostate gland. In some women, the female prostate also expels fluid during orgasm. This fluid, or female ejaculate, is quite similar to the prostatic fluid produced by the male prostate gland.