Prostate Gland: Definition, Structure, and Function


The prostate is a gland set between the bladder and the penis in human males. The gland secretes prostate fluid, a component of seminal fluid which helps sperm cells swim. The Skene’s gland is the female homolog of the prostate gland, but this article focuses solely on the prostate gland.


The prostate is about the size of a walnut, or 1.5 in, and is penetrated by the urethra that directs urine out of the body. During ejaculation, the prostate will expel an alkaline seminal fluid into the urethra. The alkaline nature of semen counters the acidic environment of the vagina. This protects sperm and prolongs the time in which sperm can be motile in the vaginal tract. The prostate gland also relies on muscles to help eject the sperm.

While the prostate gland has a simple function, it can also be a source of pain and discomfort if it becomes swollen, infected, or damaged by disease. As the gland swells, it also blocks the urethra and holds urine in the bladder. Many men, in old age, will experience a swollen prostate gland for a number of different reasons. This causes pain during urination and an inability to empty the bladder completely, and it can lead to further complications if not corrected.

Prostate Gland Function

Prostate glands have the primary function of secreting prostate fluid. The secretions of the gland, known as prostate fluid, is a part of the seminal fluid that is ejected during ejaculation. The prostate muscles will help eject the seminal fluid into the urethra. The muscles themselves weigh about twenty grams and surround the urethra just below the bladder. During ejaculation, sperm is shuttled through drainage tubes called the vas deferens and into the site of the prostate gland. The prostate’s proteolytic enzymes are able to exit the prostate through ducts that open into the urethra prior to ejaculating.

As the prostate squeezes, with the help of its surrounding muscles, it closes the opening that is found between the urethra and bladder. This directs the fluid into the urethra and pushes the semen out. The seminal fluid itself is composed of citric acid, enzymes, and zinc. While the prostate fluid is slightly acidic, the fluid produced by seminal vesicles makes the semen slightly basic. As mentioned before, is a protective measure to prolong the lifespan of each sperm.

Another element in prostate fluid is an enzyme. Known as PSA, or prostate-specific antigen, the enzyme plays a role in liquefying seminal fluid to allow sperm to swim easily. A physician can order a blood test to measure the levels of PSA in the patient’s blood. When PSA levels are high, the risk of prostate cancer is higher. The site of the prostate makes it a great location for delivering fluid; however, it also creates many difficulties when the gland swells.

Prostate Gland Location

The prostate is the largest accessory gland in males. It is found inferior to the neck of the bladder, and above the urethral sphincter (as pictured in the illustration). Moreover, the prostate lies in front of the rectum, making it easy for physicians to conduct digital rectal exams (DRE) to inspect the health of the gland. Doctors can monitor the prostate for signs of disease, such as swelling.

Prostate gland
Prostate gland and neighboring organs

Prostate Gland Structure

The prostate gland can be divided into four anatomical lobes. But a more significant delineation is a histological parsing into zones.

  • The central zone is the area that surrounds the ejaculation ducts. It derives from the Wolffian duct in human embryos.
  • The transitional zone is the area near the center that surrounds the urethra. It derives from the urogenital sinus.
  • The peripheral zone forms the body of the prostate gland. This area is located toward the backWhat and derives from the urogenital sinus.

The prostate gland is notably vascular and well-innervated. The arterial supply of oxygenated blood feeds the prostate from the prostatic arteries. In contrast, oxygen-depleted blood drains into the prostatic venous plexus and enters the iliac veins of the pelvis. The innervation of the prostate gland is a little simpler. The prostate gland is innervated by the inferior hypogastric nerve plexus. A plexus is more or less a bundle of nerves that innervate the smooth muscle of the prostate.

Prostate Gland Pathology

A swollen prostate gland will press against the urethra and at least partially block urination. This will irritate the bladder and the surrounding area. In fact, urinary discomfort secondary to gland swelling is a frequent occurrence in older gentlemen. Up to half of men over the age of sixty suffer from Benign Prostatic Hyperplasia (BPH), or the enlargement of the prostate gland. This statistic jumps to ninety percent between the ages of seventy and eighty.

The symptoms of this affliction include frequent urination and leaking. Treatment for enlarged prostate can include alpha blockers to relax the muscles around the urethra, and 5-alpha reductase inhibitors to shrink the prostate secondary to reducing the levels of DHT testosterone. Likewise, prostatitis is another condition where an infection inflames the prostate tissue. This is treated with a round(s) of antibiotics. But not all prostate growth is benign.

It is estimated that over 200,000 men are diagnosed with prostate cancer each year, per the National Cancer Institute. The five-year survival rate for men diagnosed with prostate cancer is merely 29 percent. So, a little under 30,000 deaths are caused by this disease each year. Prostate cancer takes third place in the leading causes of death in American men. A combination of surgery, radiation, and chemotherapy is used to treat prostate cancer. Removal of the prostate gland is sometimes necessary, though this can lead to additional issues.

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