What Is a Prostate and Its Functions

2010-12-13T18:03:00.000-08:00

The more you know about the normal development and function of the prostate, where it’s located, and what it’s attached to, the better you can understand how prostate cancer develops and impacts a man’s life over time—due either to cancer growth or as a result of treatments.

Normal Anatomy

The normal prostate is a small, squishy gland about the size of a walnut (20 milliliters). It sits under the bladder and in front of the rectum. The urethra—the narrow tube that runs the length of the penis and carries both urine and semen out of the body—runs directly through the prostate. The rectum, or lower end of the bowel, sits just behind the prostate and the bladder.

Sitting just above the prostate are the seminal vesicles—two little glands that secrete about 60% of the substances that make up semen. Running alongside and attached to the sides of the prostate are the nerves that control erectile function.

Normal Physiology

The prostate is not essential for life, but it’s important for reproduction. It seems to supply substances that facilitate fertilization and sperm transit and survival. Enzymes like PSA are actually used to loosen up semen to help sperm reach the egg during intercourse. (Sperm is not made in the prostate, but rather the testes.)

Other substances made by the seminal vesicles and prostate—such as zinc, citrate, and fructose—give sperm energy to make this journey. Substances like antibodies may protect the urinary tract and sperm from bacteria and other pathogens.

The prostate typically grows during adolescence under the control of the male hormone testosterone and its byproduct DHT, or dihydrotestosterone.

Prostate Zones

The prostate is divided into several anatomic regions, or zones. Most prostate cancer develops from the peripheral zone near the rectum. That’s why a digital rectal exam (DRE) is a useful screening test.

BPH, a non-cancerous prostate condition, typically develops from the transition zone that surrounds the urethra, or urinary tube. This explains why the condition is typically more symptomatic than prostate cancer.

Treatment-Related Changes

Because the prostate is close to several vital structures, prostate cancer and its treatment strategies can disrupt normal urinary, bowel, and sexual functioning.

Urinary function—Under normal circumstances, the urinary sphincters (bands of muscle tissue at the base of the bladder and at the base of the prostate) remain tightly shut, preventing urine that’s stored in the bladder from leaking out. During urination, the sphincters are relaxed and the urine flows from the bladder through the urethra and out of the body.

During prostatectomy—the surgical removal of the prostate—the bladder is pulled downward and connected to the urethra at the point where the prostate once sat. If the sphincter at the base of the bladder is damaged during this process, or if it’s damaged during radiation therapy, some measure of urinary incontinence or leakage will occur.

Bowel function—Solid waste that’s filtered out of the body moves slowly down the intestines, and, under normal circumstances, the resultant stool is excreted through the anus following conscious relaxation of the anal sphincter. Damage to the rectum caused by radiation, or more rarely, by surgery, can result in bowel problems, including rectal bleeding, diarrhea, or urgency.

Sexual function—If the erectile nerves are damaged during prostatectomy, which was standard during this type of surgery up until the mid 1980s, the ability to achieve erection is lost. Sexual desire is not affected, but severing or otherwise damaging the nerves can lead to erectile dysfunction. These nerves can also be damaged by radiation, though this process usually occurs much more slowly over time.

Modern techniques in surgery (nerve-sparing), radiation (intensity modulated radiation therapy, positioning devices, 3-D conformal technologies), and seed placement (brachytherapy) have been developed to try to minimize these side effects, and this process continues to improve.

Fertility—About 10% of men with prostate cancer have what is known as seminal vesicle invasion. This means the cancer has either spread into the seminal vesicles or has spread around them. If that occurs, seminal vesicles are typically removed during prostatectomy and targeted during radiation therapy. The loss of the prostate and the seminal vesicles renders men infertile. After surgical removal, ejaculation is dry, but orgasms may still occur.

What Is A Prostate

2009-07-21T17:47:00.000-07:00

What Is A Prostate

The prostate is a round cluster of glands located at the bottom of the bladder, about midway between the rectum and the base of the penis. The prostate encircles the urethra, the tube that expels urine from the bladder by way of the penis. The ping pong ball sized gland produces most of the fluid in semen. Contraction of the muscles in the prostate squirt fluid from into the urethra tract during ejaculation. This fluid makes up the majority of the ejaculate and transports and nourishes the sperm.

Prostate cancer is the leading cause of cancer related death for American men who don’t smoke. It is primarily a disease of aging. Men in their thirties and forties rarely develop prostate cancer, but the incidence grow steadily after the age of fifty-five. About 80 percent of all prostate cancer cases occur in men over the age of sixty-five. By the age of eighty, 4 out of 5 men have some degree of prostate cancer. Many experts feel that all men will eventually develop prostate cancer if they live long enough. The three most common prostate problems are prostatitis or inflection, prostate enlargement, and prostate cancer.

Medical professionals recommend that men have annual rectal exams as part of a health checkup from ages 40 to 70, and those with high risk and all men 50 and over should add a PSA (prostate-specific antigen) blood test every year as well. When prostate cancer is detected early and treated it has a high cure rate. Men are encouraged to discuss the options with their doctor. Based on past screenings doctors have observed that in men ages 50 to 59, the prostate cancer detection rate was basically the same whether men were screened every year or every two years. Therefore normal-risk men in their 50s can to be safely screened every other year. Since there is no cure for advanced prostate cancer, early diagnosis and treatment are essential. Since early prostate cancer normally doesn’t have any symptoms, it is extremely difficult to detect without testing. Screenings using both PSA and DRE tests have proven to be the best and only reliable method of identifying the disease when it can be still be cured easily. Almost fifty-eight percent of all cases are discovered while the cancer is still isolated and at its most treatable stage. A doctor can detect prostate cancer by digital rectal examination and by a PSA (prostate-specific antigen) blood test.

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